The document summarizes findings from the Mars Exploration Rover Opportunity regarding ancient aqueous environments at Endeavour Crater on Mars. CRISM orbital data identified a location with a spectral signature of Fe3+-rich smectite clay minerals. Opportunity investigated this area in detail called the Matijevic formation. It found fine-grained layered rocks containing spherical concretions and was cut by calcium sulfate veins. Composition data suggests the rocks formed from aqueous leaching that altered the rocks to aluminum-rich smectites. This provides evidence for water-rock interactions before and after the impact, under slightly acidic to neutral pH environments that could have been more favorable for prebiotic chemistry.
The Curiosity rover analyzed samples of Martian fines from the Rocknest site using its Sample Analysis at Mars (SAM) instrument suite. SAM detected water, sulfur dioxide, carbon dioxide, and oxygen as the major gases released when heating the fines. The water content and release temperature suggest the water is bound in amorphous materials. Much of the carbon dioxide was likely released from the decomposition of fine-grained iron or magnesium carbonates. Elevated levels of deuterium indicate recent interaction with the atmosphere. Several simple organic compounds were detected but are not definitively of Martian origin.
The ChemCam instrument on the Curiosity rover identified two main soil types on Mars - a fine-grained mafic soil and a coarse-grained felsic soil locally derived. The mafic soil is similar to widespread martian soils and dust, and possesses a ubiquitous hydrogen signature from hydrated amorphous phases. This hydration may account for a significant fraction of hydrogen detected globally on Mars. ChemCam analyses did not reveal water vapor exchange between the soil and atmosphere. The observations provide constraints on the nature and hydration of amorphous phases in the soil.
The x-ray diffraction analysis of soil samples from Rocknest at Gale Crater on Mars revealed:
1) Crystalline components including plagioclase, olivine, augite, pigeonite, and minor amounts of other phases.
2) 27±14% of the soil was amorphous material, likely containing multiple iron-bearing and volatile phases including possibly hisingerite.
3) The crystalline components are similar to martian basalts and meteorites, while the amorphous component is similar to soils on Earth like those on Mauna Kea, Hawaii.
Curiosity at gale_crater_characterization_and_analysis_of_the_rocknest_sand_s...Sérgio Sacani
The Rocknest sand shadow analyzed by the Curiosity rover on Mars was similar to coarse-grained ripples analyzed by previous rovers. It consisted of an upper layer of very coarse sand grains armoring the surface, underlain by finer grains. Analysis found the sand was around 55% crystalline material of basaltic composition and 45% amorphous iron-rich glass. This amorphous component contained the volatiles detected and was similar to soils analyzed at other Mars sites, implying the materials were locally derived from similar basaltic sources globally on Mars.
The petrochemistry of_jake_m_a_martian_mugeariteSérgio Sacani
The rock "Jake_M" was the first rock analyzed by Curiosity on Mars. It has a distinct chemical composition compared to other known Martian rocks. Jake_M has a basaltic composition but is alkaline, with over 15% normative nepheline content. Its chemical makeup is similar to terrestrial mugearites, fractionated alkaline rocks found at ocean islands and rifts. This suggests Jake_M formed through extensive fractional crystallization of an alkaline magma at elevated pressure, possibly with water. The discovery of an alkaline rock expands the diversity of known Martian igneous compositions.
A habitable fluvio_lacustrine_at_gale_crater_mars1Sérgio Sacani
The Curiosity rover discovered fine-grained sedimentary rocks in Yellowknife Bay, Gale crater, Mars that are inferred to represent an ancient lake environment. Analysis found the environment would have been habitable by microorganisms, with a neutral pH, low salinity, and variable redox states of iron and sulfur. Key biogenic elements like carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorus were detected, suggesting the environment could have supported a Martian biosphere based on chemolithoautotrophy. The habitable conditions were likely present for hundreds to tens of thousands of years. These results highlight the potential for fluvial-lacustrine environments on Mars after the Noachian period to
In situ radiometric_and_exposure_age_dating_of_the_martian_surfaceSérgio Sacani
The document summarizes research on the Sheepbed mudstone sample collected by the Curiosity rover in Gale crater on Mars. Key points:
- Potassium-argon dating of the mudstone yielded an age of 4.21 ± 0.35 billion years, consistent with the expected antiquity of rocks in Gale crater.
- Cosmogenic neon-21, helium-3, and argon-36 isotopes in the mudstone yielded concordant surface exposure ages of 78 ± 30 million years, indicating recent exposure by wind erosion rather than during initial transport and deposition.
- The mudstone's composition and mineralogy suggest it has not been heated above 200°C and may preserve
Mineralogy of a_mudstone_at_yellowknife_bay_gale_crater_marsSérgio Sacani
The document summarizes the mineralogical analysis of two mudstone samples, John Klein and Cumberland, collected from Yellowknife Bay on Mars by the Curiosity rover. X-ray diffraction analysis found that the samples contain detrital basaltic minerals, calcium sulfates, iron oxides/hydroxides, iron sulfides, amorphous material, and trioctahedral smectites. The smectite in John Klein has a basal spacing of ~10 Å indicating little water interlayer hydration, while Cumberland smectite has a spacing of ~13.2 Å, suggesting partial chloritization or interlayer ions that facilitate water retention. The mudstone minerals are similar to nearby eolian deposits but
The Curiosity rover analyzed samples of Martian fines from the Rocknest site using its Sample Analysis at Mars (SAM) instrument suite. SAM detected water, sulfur dioxide, carbon dioxide, and oxygen as the major gases released when heating the fines. The water content and release temperature suggest the water is bound in amorphous materials. Much of the carbon dioxide was likely released from the decomposition of fine-grained iron or magnesium carbonates. Elevated levels of deuterium indicate recent interaction with the atmosphere. Several simple organic compounds were detected but are not definitively of Martian origin.
The ChemCam instrument on the Curiosity rover identified two main soil types on Mars - a fine-grained mafic soil and a coarse-grained felsic soil locally derived. The mafic soil is similar to widespread martian soils and dust, and possesses a ubiquitous hydrogen signature from hydrated amorphous phases. This hydration may account for a significant fraction of hydrogen detected globally on Mars. ChemCam analyses did not reveal water vapor exchange between the soil and atmosphere. The observations provide constraints on the nature and hydration of amorphous phases in the soil.
The x-ray diffraction analysis of soil samples from Rocknest at Gale Crater on Mars revealed:
1) Crystalline components including plagioclase, olivine, augite, pigeonite, and minor amounts of other phases.
2) 27±14% of the soil was amorphous material, likely containing multiple iron-bearing and volatile phases including possibly hisingerite.
3) The crystalline components are similar to martian basalts and meteorites, while the amorphous component is similar to soils on Earth like those on Mauna Kea, Hawaii.
Curiosity at gale_crater_characterization_and_analysis_of_the_rocknest_sand_s...Sérgio Sacani
The Rocknest sand shadow analyzed by the Curiosity rover on Mars was similar to coarse-grained ripples analyzed by previous rovers. It consisted of an upper layer of very coarse sand grains armoring the surface, underlain by finer grains. Analysis found the sand was around 55% crystalline material of basaltic composition and 45% amorphous iron-rich glass. This amorphous component contained the volatiles detected and was similar to soils analyzed at other Mars sites, implying the materials were locally derived from similar basaltic sources globally on Mars.
The petrochemistry of_jake_m_a_martian_mugeariteSérgio Sacani
The rock "Jake_M" was the first rock analyzed by Curiosity on Mars. It has a distinct chemical composition compared to other known Martian rocks. Jake_M has a basaltic composition but is alkaline, with over 15% normative nepheline content. Its chemical makeup is similar to terrestrial mugearites, fractionated alkaline rocks found at ocean islands and rifts. This suggests Jake_M formed through extensive fractional crystallization of an alkaline magma at elevated pressure, possibly with water. The discovery of an alkaline rock expands the diversity of known Martian igneous compositions.
A habitable fluvio_lacustrine_at_gale_crater_mars1Sérgio Sacani
The Curiosity rover discovered fine-grained sedimentary rocks in Yellowknife Bay, Gale crater, Mars that are inferred to represent an ancient lake environment. Analysis found the environment would have been habitable by microorganisms, with a neutral pH, low salinity, and variable redox states of iron and sulfur. Key biogenic elements like carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorus were detected, suggesting the environment could have supported a Martian biosphere based on chemolithoautotrophy. The habitable conditions were likely present for hundreds to tens of thousands of years. These results highlight the potential for fluvial-lacustrine environments on Mars after the Noachian period to
In situ radiometric_and_exposure_age_dating_of_the_martian_surfaceSérgio Sacani
The document summarizes research on the Sheepbed mudstone sample collected by the Curiosity rover in Gale crater on Mars. Key points:
- Potassium-argon dating of the mudstone yielded an age of 4.21 ± 0.35 billion years, consistent with the expected antiquity of rocks in Gale crater.
- Cosmogenic neon-21, helium-3, and argon-36 isotopes in the mudstone yielded concordant surface exposure ages of 78 ± 30 million years, indicating recent exposure by wind erosion rather than during initial transport and deposition.
- The mudstone's composition and mineralogy suggest it has not been heated above 200°C and may preserve
Mineralogy of a_mudstone_at_yellowknife_bay_gale_crater_marsSérgio Sacani
The document summarizes the mineralogical analysis of two mudstone samples, John Klein and Cumberland, collected from Yellowknife Bay on Mars by the Curiosity rover. X-ray diffraction analysis found that the samples contain detrital basaltic minerals, calcium sulfates, iron oxides/hydroxides, iron sulfides, amorphous material, and trioctahedral smectites. The smectite in John Klein has a basal spacing of ~10 Å indicating little water interlayer hydration, while Cumberland smectite has a spacing of ~13.2 Å, suggesting partial chloritization or interlayer ions that facilitate water retention. The mudstone minerals are similar to nearby eolian deposits but
Volatile and organic_composition_of_sedimentary_rocks_in_yellowknife_bay_gale...Sérgio Sacani
This document summarizes the results of experiments analyzing the volatile and organic compositions of sedimentary rock samples from Yellowknife Bay in Gale Crater, Mars. The samples were obtained using the Curiosity rover's drill. Analysis found the samples released water, carbon dioxide, sulfur dioxide, oxygen, and other gases when heated. The water and oxygen releases suggest the presence of hydrated minerals like phyllosilicates and oxychlorine compounds. Small amounts of organic compounds, including chlorinated hydrocarbons, were also detected, though the carbon source is uncertain. The sediments appear to have preserved evidence of past environmental conditions and potential habitability in Yellowknife Bay.
The document summarizes the elemental geochemistry of sedimentary rocks analyzed by the Curiosity rover at Yellowknife Bay, Mars. Key findings include:
1) The rocks have compositions similar to iron-rich basalt and contain elevated levels of iron, chlorine, and calcium sulfate compared to most Martian soils.
2) Mineralogical analysis found phyllosilicates, magnetite, calcium sulfates, and an amorphous component in the mudstones.
3) Geochemical evidence suggests magnetite is likely a diagenetic mineral that formed after deposition rather than a detrital mineral delivered from another source.
4) Ternary diagrams of elemental compositions indicate secondary alteration minerals
Olivine in an_unexpected_location_on_vesta_surfaceSérgio Sacani
The document reports on the discovery of olivine on the surface of the asteroid Vesta in unexpected locations, based on data from the Dawn spacecraft's VIR instrument. Specifically:
- Olivine was found in the northern hemisphere of Vesta, rather than the southern basins where mantle rocks were expected based on previous models.
- The olivine occurs in large patches hundreds of meters across mixed with howardite regolith, unlike in meteorites where it is a minor component of diogenites.
- The amount and distribution of olivine-rich material suggests a complex evolutionary history for Vesta and is not consistent with previous ideas of olivine occurrence being associated with diogenites
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
The habitability of Proxima Centauri b - I. Irradiation, rotation and volatil...Sérgio Sacani
Proxima b is a planet with a minimum mass of 1.3 M⊕ orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass,
active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b
and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet
and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time
evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima
b’s obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and
level of triaxiality. Next we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute
the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find
that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EOH) before it reached the HZ 100–200 Myr after
its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We
conclude that Proxima b is a viable candidate habitable planet.
Radial velocity monitoring has found the signature of a Msin i = 1:3 M planet located within the Habitable Zone of Proxima
Centauri, the Sun’s closest neighbor (Anglada-Escudé et al. 2016). Despite a hotter past and an active host star the planet Proxima b
could have retained enough volatiles to sustain surface habitability (Ribas et al. 2016). Here we use a 3D Global Climate Model (GCM)
to simulate Proxima b’s atmosphere and water cycle for its two likely rotation modes (the 1:1 and 3:2 spin-orbit resonances) while
varying the unconstrained surface water inventory and atmospheric greenhouse eect (represented here with a CO2-N2 atmosphere.)
We find that a broad range of atmospheric compositions can allow surface liquid water. On a tidally-locked planet with a surface water
inventory larger than 0.6 Earth ocean, liquid water is always present (assuming 1 bar of N2), at least in the substellar region. Liquid
water covers the whole planet for CO2 partial pressures & 1 bar. For smaller water inventories, water can be trapped on the night side,
forming either glaciers or lakes, depending on the amount of greenhouse gases. With a non-synchronous rotation, a minimum CO2
pressure of 10 mbar (assuming 1 bar of N2) is required to avoid falling into a completely frozen snowball state if water is abundant.
If the planet is dryer, 0.5 bar of CO2 would suce to prevent the trapping of any arbitrary small water inventory into polar ice
caps. More generally, any low-obliquity planet within the classical habitable zone of its star should be in one of the climate regimes
discussed here.
We use our GCM to produce reflection/emission spectra and phase curves for the dierent rotations and surface volatile inventories.
We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes thanks to an angular
separation of 7=D at 1 m (with the E-ELT) and a contrast of 10 7. The magnitude of the planet will allow for high-resolution
spectroscopy and the search for molecular signatures, including H2O, O2, and CO2.
The observation of thermal phase curves, although challenging, can be attempted with JWST, thanks to a contrast of 210 5 at 10 m.
Proxima b will also be an exceptional target for future IR interferometers. Within a decade it will be possible to image Proxima b and
possibly determine whether this exoplanet’s surface is habitable.
Analysis of Surface Materials by Curiosity Mars Rover - Special CollectionCarlos Bella
Curiosity used its instruments to analyze materials along its traverse on Mars, yielding three key results:
1) It found a unique alkaline volcanic rock called "Jake_M" that is compositionally similar to rare mugearite rocks on Earth.
2) It analyzed windblown deposits and found two soil types - a common mafic type similar to global Martian soils, and a locally derived felsic type from broken down bedrock.
3) Chemical analysis of the soils found evidence of hydration in the amorphous soil components, suggesting absorbed water plays a role in Mars' global hydration signal detected from orbiters.
The Mastcam instrument on the Curiosity rover observed isolated outcrops of cemented pebbles and sand grains with textures typical of fluvial sedimentary conglomerates at three locations along the rover's traverse. The rounded pebbles indicate substantial fluvial abrasion by water flows. ChemCam analysis found the conglomerate to have a predominantly feldspathic composition, consistent with minimal aqueous alteration. The sediments were mobilized by ancient water flows that were deep and fast enough to transport pebbles several centimeters in diameter. This evidence suggests Mars once had a warmer, wetter climate that could support overland water flows, in contrast to the current hyper-arid conditions.
Evidence for widespread hydrated minerals on asteroid (101955) BennuSérgio Sacani
Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRISREx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the
form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there
is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the
visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming
previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic
chemistry to Earth.
Extensive Noachian fluvial systems in Arabia Terra: Implications for early Ma...Sérgio Sacani
Valley networks are some of the strongest lines of evidence for
extensive fluvial activity on early (Noachian; >3.7 Ga) Mars. However,
their purported absence on certain ancient terrains, such as
Arabia Terra, is at variance with patterns of precipitation as predicted
by “warm and wet” climate models. This disagreement has contributed
to the development of an alternative “icy highlands” scenario,
whereby valley networks were formed by the melting of highland ice
sheets. Here, we show through regional mapping that Arabia Terra
shows evidence for extensive networks of sinuous ridges. We interpret
these ridge features as inverted fluvial channels that formed in
the Noachian, before being subject to burial and exhumation. The
inverted channels developed on extensive aggrading flood plains. As
the inverted channels are both sourced in, and traverse across, Arabia
Terra, their formation is inconsistent with discrete, localized sources
of water, such as meltwater from highland ice sheets. Our results are
instead more consistent with an early Mars that supported widespread
precipitation and runoff.
Predictions of the_atmospheric_composition_of_gj_1132_bSérgio Sacani
GJ 1132 b is a nearby Earth-sized exoplanet transiting an M dwarf, and is amongst the most highly
characterizable small exoplanets currently known. In this paper we study the interaction of a magma
ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more
than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the
amount of O2
that can build up in the atmosphere as a result of hydrogen dissociation and loss.
We find that the magma ocean absorbs at most ∼ 10% of the O2 produced, whereas more than
90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132 b from our
simulations is a tenuous atmosphere dominated by O2
, although for very large initial water abundances
atmospheres with several thousands of bars of O2
are possible. A substantial steam envelope would
indicate either the existence of an earlier H2
envelope or low XUV flux over the system’s lifetime. A
steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132 b. Further
modeling is needed to study the evolution of CO2
or N2
-rich atmospheres on GJ 1132 b.
Phosphine gas in the cloud decks of VenusSérgio Sacani
The document reports the discovery of phosphine (PH3) gas in Venus's atmosphere based on millimeter-wave spectral detections from the JCMT and ALMA telescopes. Detections of absorption at the predicted wavelength of the PH3 1-0 rotational transition were observed to be consistent with Venus' velocity. The inferred PH3 abundance is approximately 20 parts per billion. However, the presence of PH3 in Venus' atmosphere is currently unexplained as there are no known abiotic production mechanisms for PH3 under Venus' atmospheric conditions. The PH3 could potentially originate from unknown photochemistry or geochemistry, or from the presence of life by analogy to biological PH3 production on Earth. Further observations are needed to confirm the detection
An Earth-sized exoplanet with a Mercury-like compositionSérgio Sacani
Earth, Venus, Mars and some extrasolar terrestrial planets1
have a mass and radius that is consistent with a mass fraction
of about 30% metallic core and 70% silicate mantle2
. At the
inner frontier of the Solar System, Mercury has a completely
different composition, with a mass fraction of about 70%
metallic core and 30% silicate mantle3
. Several formation or
evolution scenarios are proposed to explain this metal-rich
composition, such as a giant impact4, mantle evaporation5
or the depletion of silicate at the inner edge of the protoplanetary
disk6. These scenarios are still strongly debated.
Here, we report the discovery of a multiple transiting planetary
system (K2-229) in which the inner planet has a radius
of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth
masses. This Earth-sized planet thus has a core-mass fraction
that is compatible with that of Mercury, although it was
expected to be similar to that of Earth based on host-star
chemistry7
. This larger Mercury analogue either formed with
a very peculiar composition or has evolved, for example, by
losing part of its mantle. Further characterization of Mercurylike
exoplanets such as K2-229 b will help to put the detailed
in situ observations of Mercury (with MESSENGER and
BepiColombo8) into the global context of the formation and
evolution of solar and extrasolar terrestrial planets.
This document discusses the provenance of quartz arenite sandstones from the early Paleozoic midcontinent region of the USA. The authors present new detrital zircon geochronology data from 15 Cambrian and Ordovician quartz arenite samples. They compare this to existing data from older sedimentary basins in the region, including the Huron basin and midcontinent rift deposits. Mixing models using the older basin zircon populations indicate the early Paleozoic sandstones represent mixtures derived primarily from erosion of these two source areas.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
Abundance and isotopic_composition_of_gases_in_the_martian_atmosphere_from_th...Sérgio Sacani
The Curiosity rover measured the composition and isotopic ratios of gases in the Martian atmosphere using its Sample Analysis at Mars (SAM) instrument suite. Key findings include:
- Carbon dioxide makes up 96% of the atmosphere.
- Argon-40 and nitrogen levels are consistent with previous Viking measurements, but the 40Ar/36Ar ratio is lower and the 40Ar/N2 ratio is higher than Viking.
- Isotopic signatures of carbon and other gases support the hypothesis that Mars has lost a significant portion of its original atmosphere over geological time through atmospheric escape processes.
The GRAIL spacecraft measured the gravity field of the Moon at high resolution, allowing determination of the bulk density and porosity of the lunar crust. The analysis found:
1) The bulk density of the lunar highlands crust is 2550 kg/m3, substantially lower than previous estimates due to impact-induced porosity.
2) The average porosity of the crust is 12%, varying regionally from 4-21% and correlated with impact basins.
3) A new global crustal thickness model was constructed satisfying seismic constraints with an average thickness of 34-43 km, indicating the Moon's composition is not highly enriched compared to Earth.
Craters, boulders and regolith of (101955) Bennu indicative of an old and dyn...Sérgio Sacani
- NASA's OSIRIS-REx mission arrived at the near-Earth asteroid Bennu in December 2018 and obtained images revealing its shape and surface features.
- Bennu has a diameter of 492 meters and is classified as a rubble pile asteroid, consisting of loosely bound fragments with high porosity.
- Images show numerous large boulders on Bennu's surface, some over 50 meters in size, indicating impacts in its past. Fractured boulders and impact breccias further suggest a dynamic history.
- The surface shows signs of both ancient features from the main asteroid belt as well as more recent mass movement, with clusters of boulders in low areas and incomplete crater
The green valley_is_a_red_herring_galaxy_zoo_reveals_two_evolutionary_pathwaysSérgio Sacani
This document summarizes research using data from Galaxy Zoo, SDSS, and GALEX to study how star formation is quenched in low-redshift galaxies. The key findings are:
1) Taking galaxy morphology into account, the "green valley" is not a single transitional state, as was previously thought.
2) Only a small population of blue early-type galaxies rapidly transition across the green valley as their morphology transforms from disk to spheroid and star formation is quenched quickly.
3) The majority of blue star-forming galaxies have significant disks and retain their late-type morphology as their star formation rates decline very slowly.
4) Different evolutionary pathways are observed for early- and late-type
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
Dust production and_particle_acceleration_in_supernova_1987_a_revealed_with_almaSérgio Sacani
This document presents spatially resolved submillimeter observations of supernova remnant SN 1987A using the Atacama Large Millimeter/Submillimeter Array (ALMA). The observations reveal that at longer wavelengths (2.8 mm - 1.4 mm), the emission is from a torus associated with the supernova shock wave, while at shorter wavelengths (870 μm - 450 μm) the emission is dominated by the inner supernova ejecta. For the first time, the dust emission is unambiguously shown to originate from the inner ejecta rather than from the surrounding material, supporting theoretical models of significant dust production in supernovae. The observations also allow separation of synchrotron emission from shock-accelerated particles in
The clustering of_galaxies_in_the_sdss_iii_bossSérgio Sacani
This document summarizes the key results from a study measuring baryon acoustic oscillations (BAO) in galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of the Sloan Digital Sky Survey III (SDSS-III). The study uses a sample of nearly 1 million galaxies covering 8,500 square degrees and redshifts between 0.2-0.7. It detects the BAO feature at over 7 sigma significance in both the correlation function and power spectrum. Fittings of the BAO feature measure distances of DV=1264 Mpc at z=0.32 and DV=2056 Mpc at z=0.57, with a 1% precision, the
Volatile and organic_composition_of_sedimentary_rocks_in_yellowknife_bay_gale...Sérgio Sacani
This document summarizes the results of experiments analyzing the volatile and organic compositions of sedimentary rock samples from Yellowknife Bay in Gale Crater, Mars. The samples were obtained using the Curiosity rover's drill. Analysis found the samples released water, carbon dioxide, sulfur dioxide, oxygen, and other gases when heated. The water and oxygen releases suggest the presence of hydrated minerals like phyllosilicates and oxychlorine compounds. Small amounts of organic compounds, including chlorinated hydrocarbons, were also detected, though the carbon source is uncertain. The sediments appear to have preserved evidence of past environmental conditions and potential habitability in Yellowknife Bay.
The document summarizes the elemental geochemistry of sedimentary rocks analyzed by the Curiosity rover at Yellowknife Bay, Mars. Key findings include:
1) The rocks have compositions similar to iron-rich basalt and contain elevated levels of iron, chlorine, and calcium sulfate compared to most Martian soils.
2) Mineralogical analysis found phyllosilicates, magnetite, calcium sulfates, and an amorphous component in the mudstones.
3) Geochemical evidence suggests magnetite is likely a diagenetic mineral that formed after deposition rather than a detrital mineral delivered from another source.
4) Ternary diagrams of elemental compositions indicate secondary alteration minerals
Olivine in an_unexpected_location_on_vesta_surfaceSérgio Sacani
The document reports on the discovery of olivine on the surface of the asteroid Vesta in unexpected locations, based on data from the Dawn spacecraft's VIR instrument. Specifically:
- Olivine was found in the northern hemisphere of Vesta, rather than the southern basins where mantle rocks were expected based on previous models.
- The olivine occurs in large patches hundreds of meters across mixed with howardite regolith, unlike in meteorites where it is a minor component of diogenites.
- The amount and distribution of olivine-rich material suggests a complex evolutionary history for Vesta and is not consistent with previous ideas of olivine occurrence being associated with diogenites
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
The habitability of Proxima Centauri b - I. Irradiation, rotation and volatil...Sérgio Sacani
Proxima b is a planet with a minimum mass of 1.3 M⊕ orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass,
active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b
and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet
and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time
evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima
b’s obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and
level of triaxiality. Next we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute
the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find
that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EOH) before it reached the HZ 100–200 Myr after
its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We
conclude that Proxima b is a viable candidate habitable planet.
Radial velocity monitoring has found the signature of a Msin i = 1:3 M planet located within the Habitable Zone of Proxima
Centauri, the Sun’s closest neighbor (Anglada-Escudé et al. 2016). Despite a hotter past and an active host star the planet Proxima b
could have retained enough volatiles to sustain surface habitability (Ribas et al. 2016). Here we use a 3D Global Climate Model (GCM)
to simulate Proxima b’s atmosphere and water cycle for its two likely rotation modes (the 1:1 and 3:2 spin-orbit resonances) while
varying the unconstrained surface water inventory and atmospheric greenhouse eect (represented here with a CO2-N2 atmosphere.)
We find that a broad range of atmospheric compositions can allow surface liquid water. On a tidally-locked planet with a surface water
inventory larger than 0.6 Earth ocean, liquid water is always present (assuming 1 bar of N2), at least in the substellar region. Liquid
water covers the whole planet for CO2 partial pressures & 1 bar. For smaller water inventories, water can be trapped on the night side,
forming either glaciers or lakes, depending on the amount of greenhouse gases. With a non-synchronous rotation, a minimum CO2
pressure of 10 mbar (assuming 1 bar of N2) is required to avoid falling into a completely frozen snowball state if water is abundant.
If the planet is dryer, 0.5 bar of CO2 would suce to prevent the trapping of any arbitrary small water inventory into polar ice
caps. More generally, any low-obliquity planet within the classical habitable zone of its star should be in one of the climate regimes
discussed here.
We use our GCM to produce reflection/emission spectra and phase curves for the dierent rotations and surface volatile inventories.
We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes thanks to an angular
separation of 7=D at 1 m (with the E-ELT) and a contrast of 10 7. The magnitude of the planet will allow for high-resolution
spectroscopy and the search for molecular signatures, including H2O, O2, and CO2.
The observation of thermal phase curves, although challenging, can be attempted with JWST, thanks to a contrast of 210 5 at 10 m.
Proxima b will also be an exceptional target for future IR interferometers. Within a decade it will be possible to image Proxima b and
possibly determine whether this exoplanet’s surface is habitable.
Analysis of Surface Materials by Curiosity Mars Rover - Special CollectionCarlos Bella
Curiosity used its instruments to analyze materials along its traverse on Mars, yielding three key results:
1) It found a unique alkaline volcanic rock called "Jake_M" that is compositionally similar to rare mugearite rocks on Earth.
2) It analyzed windblown deposits and found two soil types - a common mafic type similar to global Martian soils, and a locally derived felsic type from broken down bedrock.
3) Chemical analysis of the soils found evidence of hydration in the amorphous soil components, suggesting absorbed water plays a role in Mars' global hydration signal detected from orbiters.
The Mastcam instrument on the Curiosity rover observed isolated outcrops of cemented pebbles and sand grains with textures typical of fluvial sedimentary conglomerates at three locations along the rover's traverse. The rounded pebbles indicate substantial fluvial abrasion by water flows. ChemCam analysis found the conglomerate to have a predominantly feldspathic composition, consistent with minimal aqueous alteration. The sediments were mobilized by ancient water flows that were deep and fast enough to transport pebbles several centimeters in diameter. This evidence suggests Mars once had a warmer, wetter climate that could support overland water flows, in contrast to the current hyper-arid conditions.
Evidence for widespread hydrated minerals on asteroid (101955) BennuSérgio Sacani
Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRISREx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the
form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there
is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the
visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming
previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic
chemistry to Earth.
Extensive Noachian fluvial systems in Arabia Terra: Implications for early Ma...Sérgio Sacani
Valley networks are some of the strongest lines of evidence for
extensive fluvial activity on early (Noachian; >3.7 Ga) Mars. However,
their purported absence on certain ancient terrains, such as
Arabia Terra, is at variance with patterns of precipitation as predicted
by “warm and wet” climate models. This disagreement has contributed
to the development of an alternative “icy highlands” scenario,
whereby valley networks were formed by the melting of highland ice
sheets. Here, we show through regional mapping that Arabia Terra
shows evidence for extensive networks of sinuous ridges. We interpret
these ridge features as inverted fluvial channels that formed in
the Noachian, before being subject to burial and exhumation. The
inverted channels developed on extensive aggrading flood plains. As
the inverted channels are both sourced in, and traverse across, Arabia
Terra, their formation is inconsistent with discrete, localized sources
of water, such as meltwater from highland ice sheets. Our results are
instead more consistent with an early Mars that supported widespread
precipitation and runoff.
Predictions of the_atmospheric_composition_of_gj_1132_bSérgio Sacani
GJ 1132 b is a nearby Earth-sized exoplanet transiting an M dwarf, and is amongst the most highly
characterizable small exoplanets currently known. In this paper we study the interaction of a magma
ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more
than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the
amount of O2
that can build up in the atmosphere as a result of hydrogen dissociation and loss.
We find that the magma ocean absorbs at most ∼ 10% of the O2 produced, whereas more than
90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132 b from our
simulations is a tenuous atmosphere dominated by O2
, although for very large initial water abundances
atmospheres with several thousands of bars of O2
are possible. A substantial steam envelope would
indicate either the existence of an earlier H2
envelope or low XUV flux over the system’s lifetime. A
steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132 b. Further
modeling is needed to study the evolution of CO2
or N2
-rich atmospheres on GJ 1132 b.
Phosphine gas in the cloud decks of VenusSérgio Sacani
The document reports the discovery of phosphine (PH3) gas in Venus's atmosphere based on millimeter-wave spectral detections from the JCMT and ALMA telescopes. Detections of absorption at the predicted wavelength of the PH3 1-0 rotational transition were observed to be consistent with Venus' velocity. The inferred PH3 abundance is approximately 20 parts per billion. However, the presence of PH3 in Venus' atmosphere is currently unexplained as there are no known abiotic production mechanisms for PH3 under Venus' atmospheric conditions. The PH3 could potentially originate from unknown photochemistry or geochemistry, or from the presence of life by analogy to biological PH3 production on Earth. Further observations are needed to confirm the detection
An Earth-sized exoplanet with a Mercury-like compositionSérgio Sacani
Earth, Venus, Mars and some extrasolar terrestrial planets1
have a mass and radius that is consistent with a mass fraction
of about 30% metallic core and 70% silicate mantle2
. At the
inner frontier of the Solar System, Mercury has a completely
different composition, with a mass fraction of about 70%
metallic core and 30% silicate mantle3
. Several formation or
evolution scenarios are proposed to explain this metal-rich
composition, such as a giant impact4, mantle evaporation5
or the depletion of silicate at the inner edge of the protoplanetary
disk6. These scenarios are still strongly debated.
Here, we report the discovery of a multiple transiting planetary
system (K2-229) in which the inner planet has a radius
of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth
masses. This Earth-sized planet thus has a core-mass fraction
that is compatible with that of Mercury, although it was
expected to be similar to that of Earth based on host-star
chemistry7
. This larger Mercury analogue either formed with
a very peculiar composition or has evolved, for example, by
losing part of its mantle. Further characterization of Mercurylike
exoplanets such as K2-229 b will help to put the detailed
in situ observations of Mercury (with MESSENGER and
BepiColombo8) into the global context of the formation and
evolution of solar and extrasolar terrestrial planets.
This document discusses the provenance of quartz arenite sandstones from the early Paleozoic midcontinent region of the USA. The authors present new detrital zircon geochronology data from 15 Cambrian and Ordovician quartz arenite samples. They compare this to existing data from older sedimentary basins in the region, including the Huron basin and midcontinent rift deposits. Mixing models using the older basin zircon populations indicate the early Paleozoic sandstones represent mixtures derived primarily from erosion of these two source areas.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
Abundance and isotopic_composition_of_gases_in_the_martian_atmosphere_from_th...Sérgio Sacani
The Curiosity rover measured the composition and isotopic ratios of gases in the Martian atmosphere using its Sample Analysis at Mars (SAM) instrument suite. Key findings include:
- Carbon dioxide makes up 96% of the atmosphere.
- Argon-40 and nitrogen levels are consistent with previous Viking measurements, but the 40Ar/36Ar ratio is lower and the 40Ar/N2 ratio is higher than Viking.
- Isotopic signatures of carbon and other gases support the hypothesis that Mars has lost a significant portion of its original atmosphere over geological time through atmospheric escape processes.
The GRAIL spacecraft measured the gravity field of the Moon at high resolution, allowing determination of the bulk density and porosity of the lunar crust. The analysis found:
1) The bulk density of the lunar highlands crust is 2550 kg/m3, substantially lower than previous estimates due to impact-induced porosity.
2) The average porosity of the crust is 12%, varying regionally from 4-21% and correlated with impact basins.
3) A new global crustal thickness model was constructed satisfying seismic constraints with an average thickness of 34-43 km, indicating the Moon's composition is not highly enriched compared to Earth.
Craters, boulders and regolith of (101955) Bennu indicative of an old and dyn...Sérgio Sacani
- NASA's OSIRIS-REx mission arrived at the near-Earth asteroid Bennu in December 2018 and obtained images revealing its shape and surface features.
- Bennu has a diameter of 492 meters and is classified as a rubble pile asteroid, consisting of loosely bound fragments with high porosity.
- Images show numerous large boulders on Bennu's surface, some over 50 meters in size, indicating impacts in its past. Fractured boulders and impact breccias further suggest a dynamic history.
- The surface shows signs of both ancient features from the main asteroid belt as well as more recent mass movement, with clusters of boulders in low areas and incomplete crater
The green valley_is_a_red_herring_galaxy_zoo_reveals_two_evolutionary_pathwaysSérgio Sacani
This document summarizes research using data from Galaxy Zoo, SDSS, and GALEX to study how star formation is quenched in low-redshift galaxies. The key findings are:
1) Taking galaxy morphology into account, the "green valley" is not a single transitional state, as was previously thought.
2) Only a small population of blue early-type galaxies rapidly transition across the green valley as their morphology transforms from disk to spheroid and star formation is quenched quickly.
3) The majority of blue star-forming galaxies have significant disks and retain their late-type morphology as their star formation rates decline very slowly.
4) Different evolutionary pathways are observed for early- and late-type
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
Dust production and_particle_acceleration_in_supernova_1987_a_revealed_with_almaSérgio Sacani
This document presents spatially resolved submillimeter observations of supernova remnant SN 1987A using the Atacama Large Millimeter/Submillimeter Array (ALMA). The observations reveal that at longer wavelengths (2.8 mm - 1.4 mm), the emission is from a torus associated with the supernova shock wave, while at shorter wavelengths (870 μm - 450 μm) the emission is dominated by the inner supernova ejecta. For the first time, the dust emission is unambiguously shown to originate from the inner ejecta rather than from the surrounding material, supporting theoretical models of significant dust production in supernovae. The observations also allow separation of synchrotron emission from shock-accelerated particles in
The clustering of_galaxies_in_the_sdss_iii_bossSérgio Sacani
This document summarizes the key results from a study measuring baryon acoustic oscillations (BAO) in galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of the Sloan Digital Sky Survey III (SDSS-III). The study uses a sample of nearly 1 million galaxies covering 8,500 square degrees and redshifts between 0.2-0.7. It detects the BAO feature at over 7 sigma significance in both the correlation function and power spectrum. Fittings of the BAO feature measure distances of DV=1264 Mpc at z=0.32 and DV=2056 Mpc at z=0.57, with a 1% precision, the
The baryon oscillation_spectroscopic_survey_of_sdss_iiiSérgio Sacani
This document provides an overview of the Baryon Oscillation Spectroscopic Survey (BOSS) which aims to measure baryon acoustic oscillations (BAO) in galaxy clustering over a larger volume than previous surveys. BOSS uses over 1.5 million luminous galaxies out to redshift 0.7 and over 150,000 quasar spectra between redshifts 2.15-3.5 to constrain BAO. Early BOSS results include the first detection of large-scale Lyman-alpha forest clustering and a strong BAO detection in galaxy clustering at redshift 0.57. The survey is projected to yield 1% measurements of angular diameter distance and 1.7-1.8% measurements of the expansion rate at red
This document summarizes the discovery of Kepler-413b, a Neptune-sized circumbinary planet orbiting the eclipsing binary star system Kepler-413. The planet has an orbital period of approximately 66 days and an eccentric orbit with a semimajor axis of 0.355 AU. Analysis of the Kepler light curve revealed the planet's orbit is misaligned with the binary star plane by about 2.5 degrees, causing it to sometimes fail to transit one of the stars. The orbital configuration of the system places the planet interior to the habitable zone but its obliquity may undergo fluctuations on precession timescales.
Mars surface radiation_environment_measured_with_curiositySérgio Sacani
The Radiation Assessment Detector on the Curiosity rover measured the radiation environment on the surface of Mars over approximately 300 days. It found:
1) The average absorbed radiation dose from galactic cosmic rays was 0.210 mGy/day, varying due to atmospheric and solar conditions.
2) An additional absorbed dose of about 50 μGy was measured from a solar particle event.
3) Extrapolating the surface measurements, the absorbed dose was estimated to be 76 mGy/year at 1 meter below the surface, decreasing substantially at greater depths.
Transient water vapour_at_europas_south_poleSérgio Sacani
This document summarizes observations from the Hubble Space Telescope in November and December 2012 that detected statistically significant surpluses of hydrogen and oxygen emissions above Europa's southern hemisphere. This suggests the presence of two plumes of water vapor extending 200 km high with column densities of about 1020 m-2. Previous observations in 1999 and November 2012 did not detect these plumes, indicating the plume activity varies and may depend on Europa's changing orbital phases and tidal stresses. Models of the observations are consistent with intermittent vapor plumes erupting from fractures on Europa's surface near its south pole.
Probing the jet_base_of_blazar_pks1830211_from_the_chromatic_variability_of_i...Sérgio Sacani
This document summarizes ALMA observations of the blazar PKS 1830-211 taken over multiple epochs in 2012. The blazar is lensed by a foreground galaxy, producing two resolved images (NE and SW) separated by 1". The observations were taken at frequencies corresponding to 350-1050 GHz in the blazar rest frame. Analysis of the flux ratio between the two images over time and frequency revealed a remarkable frequency-dependent behavior, implying a "chromatic structure" in the blazar jet. This is interpreted as evidence for a "core-shift effect" caused by plasmon ejection very near the base of the jet. The observations provide a unique probe of activity in the region where plasma acceleration occurs in blazar
This document summarizes evidence that submillimeter galaxies (SMGs) at redshift 3-6 may be progenitors of compact quiescent galaxies observed at redshift 2. It compares properties of a sample of z~2 quiescent galaxies with a statistical sample of z>3 SMGs in the COSMOS field. It finds that the formation redshifts of the z~2 galaxies match the observed redshift distribution of z>3 SMGs. It also finds that the space densities and properties such as sizes, stellar masses, and internal velocities of the two populations are consistent with an evolutionary connection, assuming SMG starbursts have a duty cycle of 42+40 Myr. This suggests SMGs may represent an early burst
This document introduces a special section on advances in time-lapse geophysics. It summarizes that time-lapse geophysics is an important method for monitoring complex subsurface processes over time, with applications in resource management, geohazards, environmental issues, and more. Recent innovations allow for improved 4D signal detection, more frequent/continuous monitoring, and extraction of more detailed subsurface information in near real-time. The special section aims to present state-of-the-art technical articles on time-lapse geophysics across applications, theories, data acquisition, and analysis to convey new developments and stimulate further research.
An interval of high salinity in ancient Gale crater lake on MarsSérgio Sacani
The document summarizes findings from the Curiosity rover regarding salt deposits discovered in sedimentary rocks within Gale crater on Mars. Specifically:
1) The rocks contain intermittent bulk enrichments of 30-50% calcium sulfate over about 150 meters of stratigraphy, as well as a thinner section enriched in 26-36% hydrated magnesium sulfate.
2) The salts are consistent with early diagenetic precipitation from evaporating brines, including highly concentrated magnesium-rich brines.
3) This saline interval represents a substantial change in the lake hydrology, likely reflecting variations in Mars' obliquity and orbital parameters, and supports models of stepwise climate change during the Hesperian period making environments
Evidence for plumes of water on Europa has previously been found using the Hubble Space Telescope using two
different observing techniques. Roth et al. found line emission from the dissociation products of water. Sparks et al.
found evidence for off-limb continuum absorption as Europa transited Jupiter. Here, we present a new transit
observation of Europa that shows a second event at the same location as a previous plume candidate from Sparks
et al., raising the possibility of a consistently active source of erupting material on Europa. This conclusion is
bolstered by comparison with a nighttime thermal image from the Galileo Photopolarimeter-Radiometer that shows
a thermal anomaly at the same location, within the uncertainties. The anomaly has the highest observed brightness
temperature on the Europa nightside. If heat flow from a subsurface liquid water reservoir causes the thermal
anomaly, its depth is ≈1.8–2 km, under simple modeling assumptions, consistent with scenarios in which a liquid
water reservoir has formed within a thick ice shell. Models that favor thin regions within the ice shell that connect
directly to the ocean, however, cannot be excluded, nor modifications to surface thermal inertia by subsurface
activity. Alternatively, vapor deposition surrounding an active vent could increase the thermal inertia of the surface
and cause the thermal anomaly. This candidate plume region may offer a promising location for an initial
characterization of Europa’s internal water and ice and for seeking evidence of Europa’s habitability.
1) A hydrogeophysical survey was conducted on an earthen dam to investigate factors contributing to its long-term successful operation without apparent seepage issues. 2) Geophysical methods including seismic refraction, self-potential, and electrical resistivity tomography were used to map the subsurface hydrostratigraphy and groundwater flow patterns. 3) The data indicated a preferential flow pathway beneath the dam, corresponding to a sandy-gravel layer that connects the reservoir to a downstream seepage zone. This layer may explain the dam's success by providing a controlled pathway for seepage.
Molecular water detected on the sunlit Moon by SOFIASérgio Sacani
Widespread hydration was detected on the lunar surface
through observations of a characteristic absorption feature
at 3 µm by three independent spacecraft1–3
. Whether the
hydration is molecular water (H2O) or other hydroxyl (OH)
compounds is unknown and there are no established methods to distinguish the two using the 3 µm band4. However, a
fundamental vibration of molecular water produces a spectral
signature at 6 µm that is not shared by other hydroxyl compounds5
. Here, we present observations of the Moon at 6 µm
using the NASA/DLR Stratospheric Observatory for Infrared
Astronomy (SOFIA). Observations reveal a 6 µm emission
feature at high lunar latitudes due to the presence of molecular water on the lunar surface. On the basis of the strength
of the 6 µm band, we estimate abundances of about 100 to
400 µg g−1
H2O. We find that the distribution of water over the
small latitude range is a result of local geology and is probably
not a global phenomenon. Lastly, we suggest that a majority of
the water we detect must be stored within glasses or in voids
between grains sheltered from the harsh lunar environment,
allowing the water to remain on the lunar surface.
The Moonraker mission is a proposed ESA M-class mission to study Enceladus through multiple flybys. Its goals are to 1) assess the habitability of Enceladus' subsurface ocean by analyzing plume composition, 2) understand communication between the ocean and surface, and 3) determine Enceladus' formation conditions. It would carry advanced instruments to precisely measure species, isotopes, and physical properties in the plume and on the surface. The mission aims to characterize Enceladus' potential as an abiotic and biological oasis.
Martian soil as revealed by ground-penetrating radar at the Tianwen-1 landing...Sérgio Sacani
Much of the Martian surface is covered by a weathering layer (regolith or soil) produced
by long-term surface processes such as impact gardening, eolian erosion, water weathering,
and glacial modifications. China’s first Martian mission, Tianwen-1, employed the Mars
Rover Penetrating Radar (RoPeR) to unveil the detailed structure of the regolith layer and
assess its loss tangent. The RoPeR radargram revealed the local regolith layer to be highly
heterogeneous and geologically complex and characterized by structures that resemble partial
or complete crater walls and near-surface impact lenses at a very shallow depth. However,
comparable radar data from the Lunar far side are rather uniform, despite the two surfaces
being geologically contemporary. The close-to-surface crater presented in this study shows
no detectable surface expression, which suggests an accelerated occultation rate for small
craters on the surface of Mars as compared to the rate on the Moon. This is probably due to
the relentless eolian processes on the Martian surface that led to the burial of the crater and
thus shielded it from further erosion. The high loss tangent indicates that the regolith at the
Tianwen-1 landing site is not dominated by water ice.
1) A hydro-geophysical investigation was conducted at a closed landfill site in southwestern Ontario, Canada to map the distribution of landfill leachate and subsurface geology.
2) Electromagnetic and resistivity surveys revealed an anomalous high-conductivity zone in the western half of the site, indicating the presence of landfill leachate in the upper aquifer and partially in the underlying silt/sand aquitard. No contamination was detected in the lower sand aquifer.
3) Hydrological modeling predicted that the landfill leachate plume will occupy the entire upper aquifer and most of the silt/sand aquitard within 1000 years, but the lower sand aquifer will remain
Mars exploration has been guided by the search for water. The more complex quest by Mars Science
Laboratory for habitable environments should illuminate the Martian environmental history, and
possibly deliver insights into extraterrestrial life.
The document summarizes observations of water in Jupiter's stratosphere made by the Herschel Space Observatory. Herschel/HIFI obtained a 5x5 pixel map of a water emission line, finding that water decreases from southern to northern latitudes. Herschel/PACS also obtained water maps. Infrared Telescope Facility observations of methane were used to constrain stratospheric temperatures. The latitudinal distribution of water cannot be explained by temperature variations and rules out interplanetary dust as the main water source. The observations provide evidence that Jupiter's stratospheric water originated from the 1994 Shoemaker-Levy 9 comet impacts.
The US government agencies developed a coordinated strategy from 1996-2000 to study environmental effects of historical mining on federal lands and remediate contaminated sites. The resulting dataset was compiled from state and federal sources to meet these objectives. The document discusses how geospatial data on mineralized veins/faults, iron/manganese deposits, mine portal pH values, and mining features in the Animas River watershed were analyzed in ArcGIS to understand their relationship to watershed pH levels and identify naturally occurring versus mining-related acid drainage. Spatial analysis of density rasters and 3D modeling helped illustrate this geo-spatial relationship and could be expanded in the future with additional data analysis.
An infrared transient from a star engulfing a planetSérgio Sacani
Planets with short orbital periods (roughly under 10 days) are common around stars like the Sun1,2. Stars expand as they evolve and thus we expect their close planetary companions to be engulfed, possibly powering luminous mass ejections from the host star3–5. However, this phase has never been directly observed. Here we report observations of ZTF SLRN-2020, a short-lived optical outburst in the Galactic disk accompanied by bright and long-lived infrared emission. The resulting light curve and spectra share striking similarities with those of red novae6,7—a class of eruptions now confirmed8 to arise from mergers of binary stars. Its exceptionally low optical luminosity (approximately 1035 erg s−1) and radiated energy (approximately 6.5 × 1041 erg) point to the engulfment of a planet of fewer than roughly ten Jupiter masses by its Sun-like host star. We estimate the Galactic rate of such subluminous red novae to be roughly between 0.1 and several per year. Future Galactic plane surveys should routinely identify these, showing the demographics of planetary engulfment and the ultimate fate of planets in the inner Solar System.
This document reviews exoplanet habitability. It discusses how the conventionally habitable planet requires surface liquid water, but the diversity of known exoplanets suggests planets can be habitable even if different from Earth. Over 1000 exoplanets are now known, and thousands more candidates have been identified. The habitable zone is defined as the region where a planet can have surface temperatures allowing liquid water. However, a planet in the habitable zone is not guaranteed to be habitable, as Venus and Earth demonstrate. Considering the diversity of exoplanets, a broader view of planetary habitability will maximize the chances of identifying a habitable world.
Modern water at low latitudes on Mars: Potential evidence from dune surfacesSérgio Sacani
Landforms on the Martian surface are critical to understanding the nature of surface processes in the recent
past. However, modern hydroclimatic conditions on Mars remain enigmatic, as explanations for the formation
of observed landforms are ambiguous. We report crusts, cracks, aggregates, and bright polygonal ridges on the
surfaces of hydrated salt-rich dunes of southern Utopia Planitia (~25°N) from in situ exploration by the Zhurong
rover. These surface features were inferred to form after 1.4 to 0.4 million years ago. Wind and CO2 frost processes can be ruled out as potential mechanisms. Instead, involvement of saline water from thawed frost/snow is
the most likely cause. This discovery sheds light on more humid conditions of the modern Martian climate and
provides critical clues to future exploration missions searching for signs of extant life, particularly at low latitudes with comparatively warmer, more amenable surface temperatures.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
IRJET- Space Technology on Erosion Histories of Earth and Mars IRJET Journal
This document discusses using space technology to analyze erosion histories on Earth and Mars by reconstructing ancient river channels. It proposes mapping channels identified in seismic data from the North Atlantic and Mars to model uplift rates over time. This could provide insights into mantle dynamics beneath the North Atlantic and test theories of early plate tectonics and water cycling on Mars. The methodology involves reconstructing drainage networks from terrain data, modeling river profiles, and inverting models to determine uplift histories that fit observed profiles. Analyzing erosion patterns in this way could improve understanding of geological processes on multiple planets.
Solar system exploration with space resources - Aiaa asm 2014_bp_9 final paperBryan Palaszewski
Solar System Exploration Augmented by
Lunar and Outer Planet Resource Utilization:
Historical Perspectives and Future Possibilities
Bryan Palaszewski 1
NASA John H. Glenn Research Center
Lewis Field
Cleveland, OH 44135
(216) 977-7493 Voice
(216) 433-5802 FAX
bryan.a.palaszewski@nasa.gov
Fuels and Space Propellants Web Site:
http://www.grc.nasa.gov/WWW/Fuels-And-Space-Propellants/foctopsb.htm
Establishing a lunar presence and creating an industrial capability on the Moon may lead to important new discoveries for all of human kind. Historical studies of lunar exploration, in-situ resource utilization (ISRU) and industrialization all point to the vast resources on the Moon and its links to future human and robotic exploration. In the historical work, a broad range of technological innovations are described and analyzed. These studies depict program planning for future human missions throughout the solar system, lunar launched nuclear rockets, and future human settlements on the Moon, respectively. Updated analyses based on the visions presented are presented. While advanced propulsion systems were proposed in these historical studies, further investigation of nuclear options using high power nuclear thermal propulsion, nuclear surface power, as well as advanced chemical propulsion can significantly enhance these scenarios.
Robotic and human outer planet exploration options are described in many detailed and extensive studies. Nuclear propulsion options for fast trips to the outer planets are discussed. To refuel such vehicles, atmospheric mining in the outer solar system has also been investigated as a means of fuel production for high energy propulsion and power. Fusion fuels such as Helium 3 (3He) and hydrogen can be wrested from the atmospheres of Uranus and Neptune and either returned to Earth or used in-situ for energy production. Helium 3 and hydrogen (deuterium, etc.) were the primary gases of interest with hydrogen being the primary propellant for nuclear thermal solid core and gas core rocket-based atmospheric flight. A series of analyses have investigated resource capturing aspects of atmospheric mining in the outer solar system. These analyses included the gas capturing rate, storage options, and different methods of direct use of the captured gases. While capturing 3He, large amounts of hydrogen and 4He are produced. With these two additional gases, the potential for fueling small and large fleets of additional exploration and exploitation vehicles exists.
A measurement of water vapour amid a largelyFelipe Hime
- Galileo observations of Europa showed its surface consists of chaotic terrains like pits, domes, and irregular uplifts, suggesting Europa contains a global ocean under an icy crust.
- The authors conducted a survey from 2016-2017 using infrared spectroscopy at the Keck Observatory to directly measure water vapor on Europa, resulting in non-detections on 16 of 17 dates with strict upper limits.
- On one date (April 26, 2016), a measurement of water vapor was detected at Europa's leading hemisphere, corresponding to a column density of 1.4×1019 H2O m-2 and a total water production rate exceeding previous exogenic estimates, suggesting an isolated localized endogenic plume event.
Localized aliphatic organic material on the surface of CeresSérgio Sacani
This document summarizes research on the detection of organic material on the surface of the dwarf planet Ceres. Spectral data from the Dawn spacecraft's VIR instrument shows a clear detection of an organic absorption feature at 3.4 micrometers localized near the Ernutet crater on Ceres. This signature is characteristic of aliphatic organic matter. The presence of organics as well as other compounds like ammonia-bearing minerals, water ice, carbonates and salts indicates a complex chemical environment on Ceres that could be favorable for prebiotic chemistry. The organics are concentrated in a 1000 square kilometer region near Ernutet crater, and their origin is unclear but may be from an impactor or endogenous to Ceres
The cores contain 2-4 m thick sequences of hemipelagic siliceous mud and ooze deposited under seasonally open marine conditions on the continental shelf of Mac. Robertson Land, East Antarctica over the past 15,000 years. Geochemical records from five sediment cores spanning the inner, mid, and outer shelf suggest episodes of increased accumulation of biogenic material, particularly diatoms, at around 5.5, 1.2, 3.8, 6.2, and 10.8 thousand years ago. These features likely reflect periods of enhanced diatom production over the shelf, possibly related to climatic warming. In contrast, the inner shelf core indicates relatively constant seasonal diatom production maintained by a coastal polynya
Similar to Ancient aqueous environments_at_endeavour_crater_mars (20)
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
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collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
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level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
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LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
Ancient aqueous environments_at_endeavour_crater_mars
1. Ancient Aqueous Environments at Endeavour Crater, Mars
R. E. Arvidson et al.
Science 343, (2014);
DOI: 10.1126/science.1248097
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2. RESEARCH ARTICLE
Ancient Aqueous Environments
at Endeavour Crater, Mars
R. E. Arvidson,1* S. W. Squyres,2 J. F. Bell III,3 J. G. Catalano,1 B. C. Clark,4 L. S. Crumpler,5
P. A. de Souza Jr.,6 A. G. Fairén,2 W. H. Farrand,4 V. K. Fox,1 R. Gellert,7 A. Ghosh,8
M. P. Golombek,9 J. P. Grotzinger,10 E. A. Guinness,1 K. E. Herkenhoff,11 B. L. Jolliff,1
A. H. Knoll,12 R. Li,13 S. M. McLennan,14 D. W. Ming,15 D. W. Mittlefehldt,15 J. M. Moore,16
R. V. Morris,15 S. L. Murchie,17 T. J. Parker,9 G. Paulsen,18 J. W. Rice,19 S. W. Ruff,3
M. D. Smith,20 M. J. Wolff4
Opportunity has investigated in detail rocks on the rim of the Noachian age Endeavour crater, where
orbital spectral reflectance signatures indicate the presence of Fe+3-rich smectites. The signatures
are associated with fine-grained, layered rocks containing spherules of diagenetic or impact
origin. The layered rocks are overlain by breccias, and both units are cut by calcium sulfate veins
precipitated from fluids that circulated after the Endeavour impact. Compositional data for fractures
in the layered rocks suggest formation of Al-rich smectites by aqueous leaching. Evidence is
thus preserved for water-rock interactions before and after the impact, with aqueous environments
of slightly acidic to circum-neutral pH that would have been more favorable for prebiotic chemistry
and microorganisms than those recorded by younger sulfate-rich rocks at Meridiani Planum.
he Mars Exploration Rover Opportunity
has been exploring Endeavour crater, an
impact crater ~22 km in diameter formed
in ancient Noachian materials, since August 2011
(1). Opportunity arrived at Cape York, an eroded
segment of Endeavour’s rim, where the rover traversed from the younger Burns formation sulfaterich sandstones onto the older rim rocks (2) (Fig. 1).
The rover initially traversed onto the southern tip
of Cape York, named Spirit Point, where impact
breccias were detected and characterized (1). After traversing along the western side of Cape
York and spending the martian winter near its
northern end, Opportunity traversed back south-
ward along the eastern side of Cape York when
spring arrived.
Observations from the Mars Reconnaissance
Orbiter’s (MRO’s) Compact Imaging Spectrometer for Mars (CRISM) (3, 4), acquired in an alongtrack oversampled (ATO) mode to sharpen spatial
details, were used to identify and map a Fe+3-rich
smectite mineral locality in an area on the eastern
side of Cape York called Matijevic Hill (5) (Fig. 1).
Opportunity and its Athena instrument payload
(6, 7) were then used to investigate this area in
detail for a total of 200 sols (8) to determine the
source of this mineral signature and implications
for past environmental conditions (Fig. 1).
1
CRISM Observations
An extensive ensemble of standard-mode CRISM
data with ~18 m/pixel spatial resolution has been
acquired over Endeavour crater and its rim segments since 2006 to help identify areas that expose minerals formed in aqueous environments
(9–11). CRISM observations using the ATO mode
were acquired beginning in 2010 over Cape York
to identify and map aqueous minerals in detail so
that Opportunity could then be directed to those
localities to make ground-based observations of
the relevant deposits. The CRISM ATO data were
collected by gimbaling the instrument optical system to space the normally ~18-m pixels (projected
onto the ground) to a few meters apart in the
along-track direction. Damped least-squares processing techniques were then used to sharpen the
spatial resolution to 9 m/pixel in this direction
(supplementary materials). Because Cape York is
approximately aligned along the MRO ground
track, this approach allowed identification of outcrops at a much finer spatial scale than was possible
with previous observations. Using a first-principles
approach to model the atmospheric gases, aero-
T
Department of Earth and Planetary Sciences, Washington
University in Saint Louis, St. Louis, MO 63130, USA. 2Department of Astronomy, Cornell University, Ithaca, NY 14853, USA.
3
School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA. 4Space Science Institute, Boulder,
CO 80301, USA. 5New Mexico Museum of Natural History and
Science, Albuquerque, NM 87104, USA. 6Commonwealth Scientific and Industrial Research Organization (CSIRO) Computational Informatics, Hobart 7001 TAS, Australia. 7Department of
Physics, University of Guelph, Guelph, Ontario, N1G 2W1, Canada. 8Tharsis Inc., Gaithersburg, MD 20877, USA. 9Jet Propulsion Laboratory, California Institute of Technology, Pasadena,
CA 91109, USA. 10Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125,
USA. 11U.S. Geological Survey, Astrogeology Science Center,
Flagstaff, AZ 86001, USA. 12Botanical Museum, Harvard University, Cambridge, MA 02138, USA. 13Department of Civil, Environmental, and Geodetic Engineering, Ohio State University,
Columbus, OH 43210, USA. 14Department of Geosciences,
State University of New York, Stony Brook, NY 11794, USA.
15
Astromaterials Research and Exploration Science (ARES),
NASA Johnson Space Center, Houston, TX 77058, USA. 16NASA
Ames Research Center, Moffett Field, CA 94035, USA. 17Applied Physics Laboratory, Laurel, MD 20723, USA. 18Honeybee
Robotics Spacecraft Mechanisms Corporation, Pasadena, CA
91103, USA. 19Planetary Science Institute, Tucson, AZ 85719,
USA. 20NASA Goddard Space Flight Center, Greenbelt, MD
20771, USA.
*Corresponding author. E-mail: arvidson@wunder.wustl.edu
www.sciencemag.org
SCIENCE
VOL 343
sols, and surface scattering behavior, CRISM data
for each wavelength band were reduced to surface
single scattering albedo (SSA), a parameter that
is independent of lighting and viewing conditions
(supplementary materials). For this study, the retrieved SSAs were recast to spectral radiance coefficients using the lighting and viewing conditions
for laboratory data acquired with the Brown University RELAB spectrometer system. This allowed
direct spectral feature and magnitude comparisons between RELAB and CRISM data.
Retrieved SSA spectra (0.45 to 2.5 mm) were
examined interactively for all of Cape York and
surrounding plains, along with use of standard
band depth mapping to search for evidence of
clay mineral signatures. Results show that there is
one small region, located on the Endeavour crater
side of Cape York on Matijevic Hill, that shows
2.28 and 2.39 mm Fe-OH combination absorptions diagnostic of an Fe+3-rich smectite best
matched by the mineral nontronite (12–15) (Fig. 2).
The locations exhibiting these features were mapped
using >1.0% absorption band depth criteria (Fig.
1). The ~1.9-mm band depth for the average spectrum for this location is indistinguishable from
the average spectrum for all of Cape York, which
implies a high degree of desiccation of the interlayer water (16, 17) (supplementary materials).
The lack of ~1.4-mm absorption is also consistent
with substantial desiccation. Further, the 2.28- and
2.39-mm absorptions are shallow, even compared
to laboratory-derived spectra of a mix of anhydrous
basalt and 5% by weight of Fe+3-rich smectite
(18, 19) (Fig. 2). This implies that the Fe+3-rich
smectite on Cape York likely occurs at only a few
weight percent of the exposed material.
Opportunity Observations
Overview
Opportunity was commanded to turn uphill and
start a detailed investigation of the rocks on
Matijevic Hill at the location where CRISM data
showed the Fe+3-rich smectite signature (Fig. 1).
These localities correspond to rocks subsequently
named the Matijevic formation that range from
light-toned, planar outcrops with a discontinuous
surface of darker veneers to erosionally resistant
ridges with high concentrations of small spherules
(Figs. 3 and 4). In a few locations, apparent bedding exposed in cross section is expressed as
millimeter- to centimeter-scale layers (Fig. 5).
The Matijevic formation rocks are fine-grained,
with subrounded particles ranging from ~0.3 mm
in size to below the limit of Microscopic Imager
(MI) resolution (supplementary materials). Rare
dark particles are present, with shapes that range
from angular to subrounded. The energy per volume required to grind into spherule-free exposures
of these rocks with the rover’s Rock Abrasion
Tool (RAT) is ~2.8 J/mm3, similar to soft sulfaterich sandstones elsewhere at the Opportunity site
(20) and to some of the weakest rocks found by
the rover Spirit (21).
24 JANUARY 2014
1248097-1
3. Exploring Martian Habitability
Fig. 1. Inset, top left, is a portion of a false-color HiRISE image centered on Cape York. Black outlines
Matijevic Hill as shown in the main figure with initial traverses accomplished by Opportunity to evaluate
the geologic setting of the region for which CRISM data showed the presence of Fe+3-rich smectite. Key
named locations and the Espérance target are shown, along with the location from which the sol 3132
Navcam mosaic shown in Fig. 3 was taken. Lower left shows a portion of CRISM ATO FRT0001D86B
centered on Cape York and processed to 9 m/pixel along track and projecting RGB as 2.2, 1.8, and
1.2 mm (see supplementary materials). The red region in the CRISM insert delineates where CRISM
spectra show 2.28- and 2.39-mm absorptions diagnostic of Fe+3-rich smectite. HiRISE observation
ESP_032573_1775_color.jp2.
Spherules
The spherules that are present in many Matijevic
formation rocks are found in concentrations that
range up to ~40% by volume, with highest values
at the Kirkwood locality (Fig. 7). Spherules are
typically 2 to 3 mm in diameter, with a ~5-mm
maximum diameter. Wind erosion of the spherules
has exposed concentric structures, with resistant
outer shells, less resistant interiors that are visually similar to the surrounding matrices, and
irregular and resistant internal structures. Spherules
are mostly matrix-supported, even at the Kirkwood
locality, although some are in contact with one
another. Kirkwood lacks laminar bedding, although
roughly horizontal partings accentuated by wind
erosion are weakly expressed. Spherule-rich outcrops like Kirkwood are resistant to erosion relative to materials around them and, thus, stand out
in positive relief. The RAT specific grind energy
of Kirkwood is ~23 J/mm3, ~8 times that of
spherule-free Matijevic formation rocks.
Spherules exhibit subtle compositional differences compared to the matrix in which they
Fig. 2. (A) CRISM-based, continuumremoved mean spectrum for the Fe+3rich smectite locations on Matijevic Hill,
together with a laboratory spectrum for
the mix of 95% basalt and 5% nontronite (18, 19). As explained in Supplementary materials, the increased noise
level for wavelengths less than ~2.2 mm
precludes identification of subtle metalOH absorption features for this wavelength interval. (B) Continuum-removed
laboratory spectra of 100% fine-grained
(clay-sized) montmorillonite (Al-rich),
nontronite (Fe+3-rich), and saponite
(Mg-rich) smectites are plotted. Nontronite (12) is the best spectral match to
the CRISM spectrum. Saponite spectrum
is from sample LASA59 in the RELAB archives at Brown University. Montmorillonite
spectrum is from sample SWY-2, documented in (37).
1248097-2
24 JANUARY 2014
The elemental composition of most Matijevic
formation rocks, as determined by the Alpha Particle X-Ray Spectrometer (APXS) (Table 1), is
similar to average martian soil (i.e., basaltic)
(22), similar to average martian upper crust on a
S- and Cl-free basis (23), and slightly higher in Si
and Al and lower in Fe than the Shoemaker formation impact breccias that make up most of
Cape York (1). Analysis of photon-scattering
peaks (24) in APXS data from Matijevic materials does not reveal excess light elements within
detection limits. This observation places an upper limit of ~5 weight percent (wt %) H2O in the
rock. The inferred lack of hydration is consistent
with the CRISM-based Fe+3-rich smectite detection that shows Fe-OH combination bands at 2.28
and 2.39 mm but lacks evidence for 1.4- or 1.9-mm
bands indicative of extensive interlayer water
(see the supplementary materials).
The Fe+3-rich smectite signature seen in
CRISM data likely results from the presence of
the veneers because these deposits are enriched in
elements (Zn, S, Cl, and Br) that are mobile
under aqueous conditions and match the signature from CRISM data maps to locations where
veneers are present (Figs. 1 and 3). Panoramic
camera (Pancam) spectra show that, where dust
has been brushed away using the RAT, the veneers
exhibit a subtle absorption centered over the
0.934-mm band (Fig. 6). This feature is consistent
with, but not uniquely indicative of, the presence
of a Fe+3-rich smectite electronic transition absorption (12). An equivalent feature is not apparent in CRISM spectra retrieved for the CRISM S
data (~0.45 to 1.0 mm) for the region where the
2.28- and 2.39-mm absorptions are present. This is
likely because of the subtle nature of the 0.934-mm
absorption and obscuration by wind-blown dust
that dominates spectra for these wavelengths in
most areas of Mars, including Endeavour’s rim
segments.
VOL 343
SCIENCE
www.sciencemag.org
4. RESEARCH ARTICLE
are embedded (Fig. 8). FeOT increases with
increasing spherule abundance, whereas CaO,
Al2O3, and MnO decrease. The FeOT/MnO ratio varies from <50 in spherule-free Matijevic
formation materials to >75 in spherule-rich targets, extrapolating to >100 in pure spherules.
Spherules are also slightly redder in Pancam
color images than the matrix in which they are
embedded, and cuttings produced by RAT abrasion of dense accumulations of spherules show
a subtle 0.535-mm absorption in Pancam data that
is consistent with the presence of fine-grained
iron oxides.
Impact Breccias
Overlying the Matijevic formation is a unit that is
best exposed at Copper Cliff (Figs. 1, 3, and 9A).
The contact at this location is planar and likely
an unconformity, with an abrupt transition from
the light-toned, fine-grained, orthogonally jointed
Matijevic formation rocks upward into darker rock
exposures in Copper Cliff with coarse, poorly
Fig. 3. A portion of a Navcam image mosaic acquired on sol 3132 (see Fig. 1 for
the location on Cape York) looking to the north and northeast at recessive, bright,
finely layered Matijevic formation outcrops partially covered by dark veneers.
Opportunity in situ observations were acquired for the Onaping, Sandcherry, and
Espérance targets, in addition to several targets at Whitewater Lake and Kirkwood
(see Fig. 4). The Matijevic formation materials are overlain by impact breccias
(including rocks exposed on Copper Cliff) on the upslope portion of the scene.
sorted rock clasts and no visible jointing. MI
images show Copper Cliff rocks are breccias, with
clasts up to a few centimeters in size (Fig. 9B).
Some spherules are present and show a decrease
in abundance up section.
The elemental composition of the Copper Cliff
breccias (Table 1) differs from that of Shoemaker
formation impact breccias found elsewhere on
Cape York (1), particularly near the bottom of the
section on Matijevic Hill. The lowermost target,
Onaping, has higher Al2O3 and lower FeOT than
These breccias may or may not be part of the Shoemaker formation breccias
exposed over much of Cape York. Matijevic formation outcrops extend to the
right and downhill of the scene for ~30 m, whereas in the Whitewater Lake and
Kirkwood areas, these rocks extend only ~4 m along the downslope direction.
Stratigraphic section for the local area and surroundings is shown bottom
right. The Grasberg unit includes materials that form the bench that surrounds
Cape York (1).
Fig. 4. Portion of a Pancam false-color mosaic acquired between sols 3064 to 3070 of the Kirkwood
(dark outcrop at bottom of figure) and Whitewater
Lake (planar bright outcrops with dark veneers)
areas showing the targets Azilda, Chelmsford (veneer),
and the Ortiz (veins). For scale, the distance between
the Azilda and Ortiz targets is ~60 cm. Pancam bands
L2 (0.753 mm), L5 (0.535 mm), and L7 (0.432 mm)
shown as RGB.
www.sciencemag.org
SCIENCE
VOL 343
24 JANUARY 2014
1248097-3
5. Exploring Martian Habitability
Shoemaker formation breccias, whereas other rocks
sampled that lie stratigraphically above Onaping
(Vermillion Cliffs, Vermillion Lake, and Maley)
become increasingly similar to Shoemaker formation breccias. All of these targets have high
Ni compared with other Shoemaker formation
breccias, but similar to those of the Matijevic
formation rocks.
Sulfate-Rich Veins
Both Matijevic formation rock exposures and the
overlying Copper Cliff breccias locally contain
narrow, light-toned fracture-filling veins (Fig. 10A).
Maximum widths are ~1 cm, and most are much
narrower. Multiple APXS measurements on dense
concentrations of veins show a strong correlation
of CaO with SO4 (Fig. 10B), in a ratio consistent
with a dominance by Ca-sulfate. Pancam multispectral images of the veins show a marked downturn in reflectance from 0.934 to 1.009 mm. This
same downturn has been observed for much larger
Ca-sulfate veins west of Cape York, where it was
attributed to a H2O overtone feature indicative of
the hydrated CaSO4 mineral gypsum (1, 25).
defined by planar fins and vertical laminae
that lie parallel to quasi-orthogonal joint planes.
A distinctive linear zone along one of the joint
planes, named Espérance, is ~0.5 m long, with
an irregular width reaching ~0.1 m. This area
was the site of an intensive measurement campaign. The bulk of the material in Espérance is
brighter than the host rock, with patchy darker
coatings. The chemical composition of Espérance
(Table 1) is noteworthy. After partial RAT abrasion of the target Espérance6, APXS data show
the lowest values of FeOT (4.4 wt %) and CaO
(2.1 wt %), and the highest values of SiO2
(62.5 wt %) and Al2O3 (15.4 wt %) measured
by Opportunity at Meridiani Planum. In addition, Pancam images of the brightest regions of
Espérance show a downturn in reflectance from
0.934 to 1.009 mm, consistent with the presence
of one or more hydrated mineral phases [e.g.,
hydrated silica (25)], although APXS scatterpeak ratios constrain the water content to be less
than ~5 wt %.
Boxwork Fractures
In a few locations, Matijevic formation outcrops
are cut by decimeter-scale boxwork fractures
Interpretations
The origin of Matijevic formation rocks is constrained, although not uniquely, by their finegrained and locally layered character. These rocks
have been observed, to date, only on Matijevic
Hill, and thus, broader geologic context for their
formation is lacking. Fine-grained clastic rocks
can form by impact, explosive volcanic, eolian,
or fluvial and/or lacustrine processes, and without
context, we cannot distinguish confidently among
these possibilities. If the deposits are an impactite, the fine-grained nature, with overlying coarse
breccias, implies that they are distal ejecta from
an impact that predates Endeavour, not from the
Endeavour impact itself. Whatever their origin, the
Matijevic formation exposes the oldest materials
investigated to date by Opportunity.
Fig. 5. Pancam false-color view acquired on sol 3066 of fine-scale layering in the Whitewater Lake
locality. Veneers have been resistant to wind erosion and enhanced the layered appearance of the
outcrop. Layers are typically several millimeters thick.
Table 1. Elemental chemistry of selected samples as determined by the APXS instrument, under the standard assumption of a homogeneous
APXS target matrix. FeOT denotes total iron oxides. MfLM, Matijevic formation matrix; MfLV, Matijevic formation veneer; MfSR, Matijevic formation spherulerich; CCB, Copper Cliff breccia; ESP, Espérance.
MfLM
MfLV
MfLM
MfLM
MfSR
MfSR
MfSR
CCB
CCB
CCB
CCB
ESP
ESP
ESP
Concn. (mg g−1)
Portion (wt %)
Sample
MgO
Al2O3
SiO2
2.55 7.91
Azilda1
Sandcherry1
2.83 8.64
Ortiz (no veins)
2.21 6.58
Ortiz2b (vein-rich) 2.09 6.28
Kirkwood2
2.44 8.47
Fullerton2
2.25 8.22
Sturgeon River1
2.21 9.29
Onaping
2.24 8.21
Vermilion Cliffs
2.25 8.09
Vermilion Lake
1.93 7.28
Maley2
2.24 8.17
Espérance2
2.16 6.49
Espérance63
2.25 4.73
Lihir
1.66 5.89
Dark soil4
2.34 7.33
Average error
T0.21 T0.11
Na2O
10.60
9.02
9.62
8.57
9.91
10.47
9.61
11.26
10.27
8.60
8.94
10.36
15.37
12.92
9.65
T0.13
51.2 1.50
44.7 1.33
46.5 1.23
42.0 1.17
49.1 0.74
50.1 0.89
49.5 0.59
47.0 0.99
45.0 1.04
44.4 1.14
43.6 0.99
50.6 1.26
62.5 1.14
58.4 1.19
47.0 0.85
T0.4 T0.08
1
Sample abraded using the RAT.
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2
Sample brushed using the RAT.
24 JANUARY 2014
P2O5
SO3
Cl
K2O
2.47 0.53 0.28
6.42 1.75 0.31
7.87 0.92 0.32
13.51 0.95 0.27
4.50 1.08 0.49
4.64 0.85 0.33
3.32 0.47 0.36
6.74 1.04 0.27
8.71 1.27 0.31
9.27 1.52 0.50
9.79 1.70 0.41
8.93 2.61 0.45
3.28 2.32 0.24
6.25 1.58 0.37
4.68 0.59 0.51
T0.09 T0.02 T0.06
3
CaO
MnO
FeOT
Ni
Zn
Br
5.98 0.87 0.24 0.36
7.05 0.86 0.24 0.39
7.91 0.92 0.23 0.47
10.35 0.78 0.22 0.47
5.03 0.79 0.30 0.22
5.81 0.96 0.29 0.28
5.11 0.81 0.36 0.29
6.99 0.90 0.28 0.39
7.16 0.83 0.26 0.40
7.27 1.01 0.29 0.38
7.02 0.87 0.25 0.36
5.80 0.99 0.28 0.27
2.14 0.93 0.34 0.19
4.03 1.16 0.32 0.16
7.38 0.90 0.39 0.39
T0.05 T0.07 T0.03 T0.01
15.4
16.3
15.1
13.2
16.7
14.7
17.9
13.6
14.2
16.2
15.5
9.6
4.4
5.8
17.6
T0.1
922
914
723
670
881
738
1165
684
868
818
863
707
622
644
349
T50
134
373
193
144
134
176
132
212
216
600
414
484
238
304
199
T20
48
332
157
208
112
159
57
62
312
80
85
233
35
114
24
T20
Sample partially abraded using the RAT.
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TiO2
Cr2O3
4
Typical Meridiani basaltic sand composition
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6. RESEARCH ARTICLE
Fig. 6. (A) Pancam false-color
view showing the Chelmsford
veneer after brushing using the
RAT. Brushed areas are ~3.8 cm
wide. Data acquired on sol 3098.
(B) Pancam-based spectra of
undisturbed bright layer, together with Chelmsford veneer
undisturbed and brushed surfaces. Note the presence of the
subtle absorption associated
with the Pancam data acquired
on sol 3098.
Fig. 7. (A) Pancam falsecolor image acquired on
sol 3208 of Matijevic formation rocks at the Whitewater Lake locality, showing
embedded spherules. Approximate scale across image is 40 cm. (B) MI mosaic
acquired on sol 3064 showing a dense concentration of spherules at the
Kirkwood target and locality. Approximate scale
across the scene is 5 cm,
and illumination is from
the top.
The veneers are likely the carrier of the Fe+3rich smectite signature detected from CRISM data
and are inferred to have formed either as surface
deposits or along bedding plane fractures as mildly acidic (>5 pH) (26, 27) waters were neutralized
by reactions with the finely layered strata These
produced a small amount of Fe+3-rich smectite
and salts.
Two hypotheses are considered for the origin
of the spherules: (i) diagenetic concretions and (ii)
accretionary lapilli (impact or volcanic). Textural
arguments do not by themselves eliminate either
hypothesis. Concretions with concentric zoning
(i.e., hard exteriors) similar to those observed in
Matijevic Hill spherules can form under conditions of diffusion limitation from pore waters characterized by variable pH and low, but variable,
oxygen availability (28–30). However, concentric structures are also found in some impact
lapilli (31, 32). Spherules in Matijevic formation
rocks are found dispersed through finely layered
bedding (Fig. 5). Hydraulic segregation according to particle size (and hence settling velocity)
during entrainment by fluids should lead to sorting and deposition of coarse particles before fine
particles (33). The observed dispersion of spherules
across fine bedding in Matijevic formation rocks
therefore favors an origin as concretions. Dense
concentrations of spherules are observed at
Kirkwood that fall near the high end of concretion densities found on Earth. This would require
unusual bed-by-bed variation in rates of fluid flow
or availability of nucleation sites, which occasionally does happen on Earth during formation of
concretions. Dense decimeter-thick layers of accretionary lapilli are also well documented in impact deposits and occur within a finer-grained
matrix (34).
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VOL 343
Perhaps the strongest evidence favoring a
spherule origin as concretions is the difference in
chemistry between the spherules and their matrix,
but this difference is subtle (Fig. 8). If the spherules
are concretions, they must be lightly cemented as
compared to the hematite-rich concretions of the
Meridiani plains (2). Extrapolating compositional
data for spherule-rich rocks to 100% spherules
suggests only about 20% FeOT (Fig. 8). If the
change in FeOT concentration reflects an increase
in Fe+3, then cementation may involve a small
proportion of ferric oxide or oxyhydroxide, consistent with the spectral properties of spherule
cuttings. The increased FeOT/MnO in spherulerich targets is consistent with changing redox
and/or pH conditions such that Fe+2 in solution
oxidized to Fe+3 and precipitated as a thin cement, whereas Mn+2 continued in solution to
precipitate elsewhere. Interpretation of spherules
as lapilli would require layer-specific alteration
during diagenesis; therefore, both hypotheses invoke groundwater flow within Matijevic formation rocks.
The rocks exposed at Copper Cliff and higher
up the side of Matijevic Hill are impact breccias
that probably date from the Endeavour impact
event. They are either part of or are overlain by
Shoemaker formation breccias exposed over
much of Cape York (1) and are the stratigraphically lowest breccias examined by Opportunity
to date. The spherules they contain may have been
released from the Matijevic formation rocks during impact and mixed into the breccias. The different chemical compositions of the lower Copper
Cliff breccias, as compared to Shoemaker formation breccias, also suggests some admixture of
Matijevic materials, moderate aqueous alteration
after emplacement, and/or a differing provenance
reflected in a higher feldspathic/mafic ratio in the
lithic fragments. The high Ni content suggests Ni
mobilization by alteration fluids subsequent to
emplacement of the breccias.
The sulfate-rich veins observed in both the
Matijevic formation and at Copper Cliff formed
when narrow fractures were filled by calcium
sulfate precipitated from fluids generated within
the underlying Noachian crust. Calcium sulfate
was likely precipitated closest to the Noachian
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1248097-5
7. Exploring Martian Habitability
source rocks, rather than other sulfates (e.g.,
MgSO4·nH2O; FeSO4·nH2O) or chlorides, because of its lower solubility in most aqueous
fluids. The veins postdate the Copper Cliff breccias,
so this aqueous activity postdates the Endeavour
impact, which suggests that impact-driven hydrothermal flow could have been a factor. Centimeterwidth, linear gypsum veins have also been observed
adjacent to Cape York (1), and the narrower and less
regular veins of Matijevic Hill could date from
the same episode, although no observed geologic
relations confirm this.
The distinctive chemistry of Espérance indicates substantial aqueous alteration, particularly
when viewed in the classical ternary diagram of
mole fraction Al2O3 – (CaO + Na2O + K2O) –
(FeOT + MgO) (Fig. 11B). In this diagram, silicate
minerals that plot along and below the feldspar–
(FeOT + MgO) join are igneous, whereas, above
the join, secondary clay minerals dominate (35).
Data for spherule-rich rocks plot toward the
FeOT + MgO apex, whereas data for veins plot
toward the CaO + Na2O + K2O apex, consistent
with compositional inferences discussed in previous paragraphs. Six APXS measurements were
made on Espérance, culminating in the target
Espérance6 that was partially abraded with the
RAT, plus a seventh nearby point called Lihir
(Fig. 11A). These data define a near-vertical trend
in the diagram that is interpreted as a mixing line
between typical Matijevic formation rocks and
the underlying altered rock best represented by
Espérance6. Results are consistent with a high
concentration of an Al-rich smectite. The Espérance
data also show a positive correlation between
Al2O3 and SiO2, with excess silica indicated at
low Al2O3 values (Table 1). A mineral assemblage that includes substantial amounts of Al-rich
smectite and a siliceous phase or phases provides
compelling evidence for substantial aqueous alteration. In addition, the loss of iron implies that
the fluid was reducing because ferric oxides would
have been generated under oxidizing conditions
at all but very low pH values.
The boxwork fractures at Espérance and elsewhere are similar to the parallel slablike foliations
commonly associated with mineral volume changes
at uniform depths on rock exteriors and could
have presented pathways for fluid flow. The strong
localization of alteration along these fractures
indicates that the alteration occurred in place, after the fractures formed.
The events recorded at Matijevic Hill imply
an aqueous environment different from those
that produced the overlying sulfate-rich Burns
formation sandstones. Deposition began with
fluvial, eolian, distal impact or explosive volcanic
emplacement of layered, fine-grained deposits
that dominate the Matijevic formation. These
materials underwent minor aqueous modification that generated Fe+3-rich smectite and locally more intense alteration by enhanced fluid
flow along fractures that generated relatively high
concentrations of clay minerals and hydrated
silica-rich materials. Breccias were subsequently
Fig. 8. Oxide concentrations in spherulebearing targets are plotted as a function of the fraction of the APXS field of
view filled by spherules as determined
from MI images. Error bars represent 2-s
error for precision of the measurements.
Fig. 9. (A) Portion of a Pancam false-color
mosaic acquired over sols 3137-3150, showing dark-toned impact breccias of the
Copper Cliff outcrop overlying lightertoned Matijevic formation materials. The
width across the dark outcrops is ~1.5 m.
Location of Onaping MI mosaic shown in
(B) is indicated by circle. (B) MI mosaic acquired on sol 3158, showing breccia clasts,
spherules, and light-toned veins in the
target Onaping. Approximate scale across
the image is 6 cm, and illumination is from
the top.
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8. RESEARCH ARTICLE
Fig. 10. (A) MI mosaic acquired on sol 3189 of the vein-rich
location named “Ortiz” at the Whitewater Lake locality,
merged with coregistered Pancam enhanced color data.
Circles show the fields of view of four APXS measurements.
Circle diameters are 3.8 cm. (B) CaO versus SO3 for the APXS
placements on Ortiz tragets (multiple measurements were
made at some locations). Error bars are relative counting
statistics, 2s.
Fig. 11. (A) Pancam false-color view acquired on sol 3230 showing the boxwork structure and examined in detail. Circle indicates the targets Espérance6
(which was abraded with the RAT) and Lihir. Approximate scale across the scene
is 70 cm. (B) Ternary plot of mole fraction Al2O3 – (CaO + Na2O + K2O) – (FeOT + MgO)
emplaced above the Matijevic formation, probably
by the Endeavour impact. Subsequently, postimpact fluid circulation, perhaps including impacttriggered hydrothermal flow, led to precipitation
of Ca-sulfate veins in fractures that cut through
both the Matijevic formation and the overlying
Copper Cliff breccias.
The aqueous modification of Matijevic materials provides evidence for the earliest episode
of water activity documented by Opportunity. In
particular, the unusual chemistry of Espérance
points to an early period of localized intense al-
for selected rocks from Matijevic Hill (Table 1) and other materials. Mineral
compositions based on idealized stoichiometry, the field for montmorillonite
based on structural formulae of 25 natural montmorillonites (38, 39), and
average martian crust and soils taken from (23).
teration under fluid-dominated, near-neutral to
modestly low pH and reducing conditions that
would, at least transiently, have been more favorable to life or prebiotic chemistry (36) than the
very low acidic conditions recorded by younger
Burns formation sulfate-rich sandstones.
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9. Exploring Martian Habitability
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Acknowledgments: This work was supported by NASA. The
CRISM operations team at the Applied Physics Laboratory,
Johns Hopkins University, and the Opportunity operations team
at the Jet Propulsion Laboratory, California Institute of
Technology were responsible for planning and acquiring the
relevant data. The NASA Planetary Data System through the
Geosciences Node (http://pds-geosciences.wustl.edu/)
provides access to the CRISM and Opportunity data used
in this paper.
Supplementary Materials
www.sciencemag.org/content/343/6169/1248097/suppl/DC1
Materials and Methods
Figs. S1 to S8
Table S1
References (40–46)
10.1126/science.1248097
www.sciencemag.org