The two largest impact basins recently discovered at Vesta's south pole are Rheasilvia and Veneneia. Rheasilvia is ~500 km wide and 19 km deep, making it one of the largest impact features on Vesta. It has a central massif and spiral ridge patterns on its floor. Veneneia is an older, partially buried ~400 km basin located beneath Rheasilvia. Crater counts date both basins to 1-2 billion years old, indicating major geological resetting of Vesta occurred relatively recently.
Reptilian Undersea Base Destroyed - 5.1 Quake Nicobar IslandsTolec
A 5.1 magnitude earthquake occurred at 18:31:57 PM (UTC), Thursday night, February 15, 2012 in the area of Nicobar Islands, south east of the Bay of Bengal. This specific quake was the trigger event for the Procyon people of the Andromeda Council to take out & destroy a massive, extensive, Draco & Hydra Reptilian controlled & operated undersea base located on the top of the "Ninetyeast Ridge". A written transcript of this official news report can be downloaded for free at: www.andromedacouncil.com.
the slides about the solar system and beyond. to assist the grade seven and eight with better understandin of the planets and the sun, and how are they scintificaly linked.
Reptilian Undersea Base Destroyed - 5.1 Quake Nicobar IslandsTolec
A 5.1 magnitude earthquake occurred at 18:31:57 PM (UTC), Thursday night, February 15, 2012 in the area of Nicobar Islands, south east of the Bay of Bengal. This specific quake was the trigger event for the Procyon people of the Andromeda Council to take out & destroy a massive, extensive, Draco & Hydra Reptilian controlled & operated undersea base located on the top of the "Ninetyeast Ridge". A written transcript of this official news report can be downloaded for free at: www.andromedacouncil.com.
the slides about the solar system and beyond. to assist the grade seven and eight with better understandin of the planets and the sun, and how are they scintificaly linked.
Star formation at the smallest scales; A JWST study of the clump populations ...Sérgio Sacani
We present the clump populations detected in 18 lensed galaxies at redshifts 1 to 8.5 within the lensing cluster field SMACS0723.
The recent JWST Early Release Observations of this poorly known region of the sky have revealed numerous point-like sources
within and surrounding their host galaxies, undetected in the shallower HST images. We use JWST multiband photometry and
the lensing model of this galaxy cluster to estimate the intrinsic sizes and magnitudes of the stellar clumps. We derive optical
restframe effective radii from <10 to hundreds pc and masses ranging from ∼ 105
to 109 M, overlapping with massive star
clusters in the local universe. Clump ages range from 1 Myr to 1 Gyr. We compare the crossing time to the age of the clumps
and determine that between 45 and 60 % of the detected clumps are consistent with being gravitationally bound. On average,
the dearth of Gyr old clumps suggests that the dissolution time scales are shorter than 1 Gyr. We see a significant increase in the
luminosity (mass) surface density of the clumps with redshift. Clumps in reionisation era galaxies have stellar densities higher
than star clusters in the local universe. We zoom in into single galaxies at redshift < 6 and find for two galaxies, the Sparkler and
the Firework, that their star clusters/clumps show distinctive colour distributions and location surrounding their host galaxy that
are compatible with being accredited or formed during merger events. The ages of some of the compact clusters are between
1 and 4 Gyr, e.g., globular cluster precursors formed around 9-12 Gyr ago. Our study, conducted on a small sample of galaxies,
shows the potential of JWST observations for understanding the conditions under which star clusters form in rapidly evolving
galaxies.
NEAR-IR SPECTRAL OBSERVATIONS OF THE DIDYMOS SYSTEM - DAILY EVOLUTION BEFORE ...Sérgio Sacani
Ejecta from Dimorphos following the DART mission impact, significantly increased the brightness of
the Didymos-Dimorphos system, allowing us to examine sub-surface material. We report daily nearIR spectroscopic observations of the Didymos system using NASA’s IRTF, that follow the evolution
of the spectral signature of the ejecta cloud over one week, from one day before the impact. Overall,
the spectral features remained fixed (S-type classification) while the ejecta dissipated, confirming both
Didymos and Dimorphos are constructed from the same silicate material. This novel result strongly
supports binary asteroid formation models that include breaking up of a single body, due to rotational
breakup of km-wide bodies.
At impact time +14 and +38 hours, the spectral slope decreased, but following nights presented
increasing spectral slope that almost returned to the pre-impact slope. However, the parameters of
the 1 µm band remained fixed, and no ”fresh” / Q-type-like spectrum was measured. We interpret
these as follow: 1. The ejecta cloud is the main contributor (60 − 70%) to the overall light during
the ∼ 40 hours after impact. 2. Coarser debris (≥ 100 µm) dominated the ejecta cloud, decreasing
the spectral slope (after radiation pressure removed the fine grains at ≤ 10 hours after impact); 3.
after approximately one week, the ejecta cloud dispersed enough to make the fine grains on Didymos
surface the dominating part of the light, increasing the spectral slope to pre-impact level. 4. a
negligible amount of non-weathered material was ejected from Dimorphos’ sub-surface, suggesting
Dimorphos was accumulated from weathered material, ejected from Didymos surface.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
The Schwadron IBEX Ribbon Retention Theory and its possible Impact on Astrono...Peter Palme 高 彼特
Ribbon in Space around our Solar Syxstem discovered by IBEX – NASA
Will it have an impact on the current solar system and planet formation theory ?
Further:
Researchers from the University of Michigan announced today the discovery of tiny amounts of water in the moon rocks brought back to Earth by the Apollo missions were native water, and not water brought by meteors or other objects from space crashing into it. This discovery could in turn invalidate the current theory of how our Moon was formed
Youxue Zhang -
Peter Higgs - Higgs Boson - vacuum instability -
cylcle Universe formation - Galaxy formation
Joseph Lykken, a theoretical physicist at the Fermi National Accelerator Laboratory in Batavia, Ill., said Monday (Feb. 18) at the annual meeting of the American Association for the Advancement of Science
A YOUNG PROTOPLANET CANDIDATE EMBEDDED IN THE CIRCUMSTELLAR DISK
Sascha P. Quanz1,2, Adam Amara2, Michael R. Meyer2, Matthew A. Kenworthy3, Markus Kasper4, and Julien H. Girard are currently observing a formation of a protoplanet
Hector Acre Yale University Herbig-Haro 46/47 ALMA Astrophysical Journal
NASA Van Allen Probes
Geoff Reeves
Andrew Hodges, mathematical physicist at Oxford University
Jacob Bourjaily, theoretical physicist at Harvard University
quantum field theory
Nima Arkani-Hamed, lead author, professor of physics at the Institute for Advanced Study in Princeton, N.J.
Amplituhedron
David Skinner, theoretical physicist at Cambridge University
Parke and Taylor guessed a simple one-term expression
BCFW recursion relations, named for Ruth Britto, Freddy Cachazo, Bo Feng and Edward Witten.
leading mathematicians such as Pierre Deligne, Arkani-Hamed and his collaborators discovered that the recursion relations and associated twistor diagrams corresponded to a well-known geometric object. In fact, as detailed in a paper posted to arXiv.org in December by Arkani-Hamed, Bourjaily, Cachazo, Alexander Goncharov, Alexander Postnikov and Jaroslav Trnka, the twistor diagrams gave instructions for calculating the volume of pieces of this object, called the positive Grassmannian.
Hermann Grassmann, a 19th-century German linguist and mathematici
Arkani-Hamed and Trnka discovered that the scattering amplitude equals the volume of a brand-new mathematical object — the amplituhedron
Neal Turner and colleagues at NASA's Jet Propulsion Laboratory developped a three dimensional model where magnetism plays a key role in planet formation.
Laura Mersini-Houghton has so far the best theory to answer for the formation of galaxies. The Theory of the Landscape Multiverse The theory and its predictions are derived from fundamental physics and first principles by using quantum cosmology for the wavefunction of the universe on the landscape and calculating decoherence and quantum entanglement among various surviving branches
Chariklo Felipe Braga-Ribas National Observatory in Brazil
Similar to Geologically recent big_impact_basins_in_vesta (20)
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⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
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.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
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- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
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Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
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Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
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Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
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Elevating Tactical DDD Patterns Through Object CalisthenicsDorra BARTAGUIZ
After immersing yourself in the blue book and its red counterpart, attending DDD-focused conferences, and applying tactical patterns, you're left with a crucial question: How do I ensure my design is effective? Tactical patterns within Domain-Driven Design (DDD) serve as guiding principles for creating clear and manageable domain models. However, achieving success with these patterns requires additional guidance. Interestingly, we've observed that a set of constraints initially designed for training purposes remarkably aligns with effective pattern implementation, offering a more ‘mechanical’ approach. Let's explore together how Object Calisthenics can elevate the design of your tactical DDD patterns, offering concrete help for those venturing into DDD for the first time!
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
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A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
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GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
1. The Geologically Recent Giant Impact Basins at Vesta's South Pole
Paul Schenk et al.
Science 336, 694 (2012);
DOI: 10.1126/science.1223272
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2. REPORTS
main-belt impact rate. The knowledge that the event Acknowledgments: We thank the Dawn Science, Instrument, Supplementary Materials
did happen in 4.5 Gy implies a 25% probability of and Operations Teams for support. This work was supported www.sciencemag.org/cgi/content/full/336/6082/690/DC1
occurrence in the past 1 Gy. by the Italian Space Agency and NASA’s Dawn at Vesta Participating Materials and Methods
29. F. Marzari et al., Astron. Astrophys. 316, 248 (1996). Scientists Program. A portion of this work was performed at the Figs. S1 to S3
30. M. C. De Sanctis et al., Science 336, 697 (2012). Jet Propulsion Laboratory, California Institute of Technology, References (32–43)
31. A. Morbidelli, W. F. Bottke, D. Nesvorny, H. F. Levison, under contract with NASA. S. Marchi thanks Istituto Nazionale 5 January 2012; accepted 16 April 2012
Icarus 204, 558 (2009). d’Astrofisica for the support in carrying on this work. 10.1126/science.1218757
posite sides of the basin. Fractured slump blocks
The Geologically Recent Giant Impact are observed at the base of these rim scarps
[figure 3 in (10)]. The ridged slump material on
Basins at Vesta’s South Pole the rim has a more coherent structure than that
of the rugged slump material on the flank of the
Paul Schenk,1* David P. O’Brien,2 Simone Marchi,3 Robert Gaskell,2 Frank Preusker,4 central massif. This may reflect a difference in
Thomas Roatsch,4 Ralf Jaumann,4 Debra Buczkowski,5 Thomas McCord,6 Harry Y. McSween,7 rock properties, with the rim flank being less
David Williams,8 Aileen Yingst,2 Carol Raymond,9 Chris Russell10 fragmented than the central massif.
All terrains within ~100 km of Rheasilvia’s
Dawn’s global mapping of Vesta reveals that its observed south polar depression is composed of two rim (and further in some areas) show evidence
overlapping giant impact features. These large basins provide exceptional windows into impact processes at of extensive mantling by debris (Fig. 3), which
Downloaded from www.sciencemag.org on May 10, 2012
planetary scales. The youngest, Rheasilvia, is 500 kilometers wide and 19 kilometers deep and finds its is consistent with ejecta deposition. Smooth and
nearest morphologic analog among large basins on low-gravity icy satellites. Extensive ejecta deposits occur, striated surfaces are common, and nearly com-
but impact melt volume is low, exposing an unusual spiral fracture pattern that is likely related to faulting plete erasure of craters within 50 km or so of
during uplift and convergence of the basin floor. Rheasilvia obliterated half of another 400-kilometer-wide the rim (Fig. 1) gives way to the north to de-
impact basin, Veneneia. Both basins are unexpectedly young, roughly 1 to 2 billion years, and their creasing degrees of partial burial of craters
formation substantially reset Vestan geology and excavated sufficient volumes of older compositionally (Fig. 3), which is consistent with the observed in-
heterogeneous crustal material to have created the Vestoids and howardite–eucrite–diogenite meteorites. crease in crater densities away from the Rheasilvia
rim (11) and the thinning of ejecta. Differences
ubble Space Telescope (HST) imaging and central depressions associated with large in crater density provide indirect evidence for
H of asteroid Vesta revealed a major de-
pression at the south pole that is inferred
to be a giant impact basin (1) nearly as large as
multiring basins on the Moon or Mercury (8)—
are absent at Rehasilvia. Dawn instead observed
three main structural components (Fig. 1 and fig.
nonunoform ejecta deposition, but no direct evi-
dence for the extreme predicted asymmetric ejec-
ta deposition due to rotation (12) has as yet been
Vesta itself. A large basin fit well with the par- S1): a large central massif, a broad sloping basin found. The multispectral color signature most
adigm of Vesta as the parent body of the HED floor, and an outer margin. The central massif is a consistent with diogenite (13, 14) is offset from
(howardite–eucrite–diogenite) meteorites, on the 180-km-wide, 20-to-25-km-high conical dome the basin center toward 45°E longitude (fig. S1)
basis of spectroscopic and petrologic evidence (Fig. 1), with a “craggy” surface of small irregular (15) and suggests either oblique impact and en-
(2, 3), proximity to asteroid resonances that can rounded knobs and patches of relatively smooth hanced ejecta deposition in one direction or that
deliver material to near-Earth space (4), and the material on steep slopes. The knobs may represent the impact occurred in a compositionally heter-
dynamically related family of “Vestoids” (5), with exposures of uplifted fractured or disrupted bed- ogenous region, possibly because of the forma-
the basin as the likely source of these bodies. rock material, and the smoother material may be tion of older basins such as Veneneia.
Determination of the structure, shape, and age of unconsolidated debris, impact melt drained down The basic structure at Rheasilvia is surprising-
this feature—all of which provide critical param- slope, or both. Two arcuate scarps ~5 to 7 km high ly similar to that observed in very large craters on
eters for modeling the formation of Vestoids and near the crest of the central massif suggest partial low-gravity worlds elsewhere in the solar system
HEDs—are key Dawn objectives (6). failure of the central massif. The rugged surface (Fig. 1) (15). Large impact craters on the midsize
Dawn has resolved Vesta’s south polar fea- morphology is consistent with uplift of highly icy satellites Hyperion, Rhea, and Iapetus are also
ture into two large distinct overlapping impact ba- disrupted material during impact, as observed in characterized by deep steep-sided depressions
sins. The largest and youngest of these, Rheasilvia large complex craters on other bodies (8). and broad domical central peaks that account for
(Fig. 1 and fig. S1), is centered at 301° W, 75° S, The bowl-shaped floor of Rheasilvia is a 0.35 to 0.5 of the crater diameter (D) (compared
~15° from the south pole and, at ~500 T 25 km broad annular unit characterized by rolling plains. with 0.36 for Rheasilvia). These basins also have
(or ~114° of arc) in diameter and 19 T 6 km deep The floor is pervasively deformed by linear and Dcrater /Dtarget ratios of 0.4 to 0.9 compared with
(7), is both deeper and larger than estimated curvilinear ridge and inward-facing scarps 1 to 5 0.95 for Rheasilvia. This basic morphology, in
from HST (1). The multiple concentric terraces km high (Fig. 2) forming well-organized radial which large central uplift (Fig. 1 and fig. S2) dom-
and ring scarps—broad flat-lying melt sheets and (clockwise) spiral patterns extending from inates over rim failure, may be characteristic of
within the central massif out to the basin margins. large complex crater formation on smaller plane-
1
Lunar and Planetary Institute, Houston, TX 77058, USA. 2Plan- Flat-lying deposits indicative of deep ponded im- tary bodies or on bodies where melt production
etary Science Institute, Tucson, AZ 85719, USA. 3NASA Lunar pact melt and debris are absent within Rheasilvia is low, regardless of composition (15), although
Science Institute, Boulder, CO 12489, USA. 4Institute of Plan- (Fig. 1). This is consistent with the low apparent planetary curvature may also play a role.
etary Research, Deutsches Zentrum für Luft- und Raumfahrt,
volumes of impact melt found in other fresh cra- The pervasive spiral deformation pattern with-
Berlin 80302, Germany. 5Applied Physics Laboratory, Johns
Hopkins University, Laurel, MD 20723, USA. 6Bear Fight Institute, ters on Vesta and consistent with models sug- in Rheasilvia (Fig. 2) is not commonly observed
Wintrop, WA 98862, USA. 7Department of Earth and Planetary gesting that melt production would be limited on on other bodies. The involvement of the entire
Sciences, University of Tennessee, Knoxville, TN 37996, USA. asteroids because of lower impact velocities (9). basin floor in a coherent structural pattern indi-
8
School of Earth and Space Exploration, Arizona State University, The outer margin or rim of Rheasilvia has a cates that deep crustal fracturing during prompt
Tempe, AZ 85287, USA. 9Jet Propulsion Laboratory, Pasadena, CA
91109, USA. 10Department of Earth and Space Sciences, Uni- broadly hexagonal shape and is variable in ele- uplift and radial convergence of basin floor rock
versity of California, Los Angeles, Los Angeles, CA 90095, USA. vation and morphology, forming a broad ridge in was probably involved. Similar expressions of
*To whom correspondence should be addressed. E-mail: most areas (Fig. 1) and two steep inward-facing arcuate and spiral structures (15) are found across
schenk@lpi.usra.edu cuspate scarps ~15 to 20 km high (Fig. 1) on op- the floors of eroded and exposed complex cra-
694 11 MAY 2012 VOL 336 SCIENCE www.sciencemag.org
3. REPORTS
ters on Earth (16, 17), within part of the floor of Coriolis effects cannot fracture rock but may tered at 170°E, 52°S, Veneneia was first recog-
King crater on the Moon (Fig. 2 and fig. S3), have influenced the selection of specific fault nized in the global topography and is not obvious
and in experimental modeling involving radial and failure orientations (curving east rather than from the global mosaic because of the disrup-
convergence of rock material (18). Formation west). That these patterns are so dramatically tion and obscuration caused by Rheasilvia. The
of Rheasilvia would have taken roughly half of expressed at Rheasilvia is probably related to floor of Veneneia is characterized by a rolling
a Vesta rotation period (12), however, which is the absence of large volumes of obscuring im- landscape cut by disorganized short sharps and
more than enough time for coriolis effects to in- pact melt on the basin floor. ridges. A partially preserved scarp and ridge oc-
fluence the flow of rock toward basin center. The second large south polar impact feature curs along much of the remaining topographic
We suggest on the basis of the above examples on Vesta consists of a semicircular bowl-shaped rim. No central massif is observed at Veneneia,
that structural failure induced by upward and ra- depression ~400 T 25 km in diameter and 12 T but the rim scarp and thickest zone of Rheasilvia
dial convergence of rocky material during basin 2 km deep (7) named Veneneia (Fig. 1), half of ejecta pass through the central region, and much
collapse produced the observed spiral patterns. which has been destroyed by Rheasilvia. Cen- of what remains of Veneneia was likely disrupted,
Fig. 1. Comparison of large impact features on (top)
Vesta, (center) Hyperion, and (bottom) Iapetus. Vesta
image is shaded relief view of global topographic map at
150 m resolution showing the southern hemisphere.
Hyperion view is from Cassini and was obtained in 2005
with a resolution of 125 m. Iapetus view is from a Cassini-
Downloaded from www.sciencemag.org on May 10, 2012
derived global mosaic at 400 m resolution. All views are
scaled so that basins appear the same size, showing
Rheasilvia and Veneneia (~500 km and 400 km,
respectively), unnamed basin on Hyperion (~330 by 150
km) and Engelier on Iapetus (D ~ 450 km). Arrows
highlight large old basins truncated by younger basins on
both Vesta and Iapetus.
Fig. 2. Spiral deformation patterns within impact craters on (left) Vesta
and the (right) Moon. View at left shows portion of Rheasilvia basin floor
(illumination is from top left). Large dome at top right is the central
mound. View at right shows Lunar Reconnaissance Orbiter Camera–Wide
Angle view of King crater (D = 72 km) at ~100 m resolution showing
arcuate ridges and scarps on the southeast floor of the crater with similar
pattern. Large massifs at top left are part of the central peak; rim is at
bottom.
www.sciencemag.org SCIENCE VOL 336 11 MAY 2012 695
4. REPORTS
Fig. 4. Crater counts and ages for Rheasilvia
(solid triangles) and Veneneia (gray circles) ba-
sins. Estimated ages (12) are 1.0 T 0.2
(Rheasilvia) and 2.1 T 0.2 billion years (Veneneia).
Downloaded from www.sciencemag.org on May 10, 2012
The proximity of the two large basins of of Vestoids (21) could potentially be explained by
similar age near the south pole suggests the ejecta from the somewhat older giant Veneneia
possibility of a binary asteroid impact. However, basin (Fig. 1), which has a nominal excavation
the arcuate rim of Rheasilvia clearly truncates volume ~65% that of Rheasilvia and likely
Veneneia, and there is no indication that the ex- excavated an additional several 105 km3 to space.
panding ejecta or basin of Veneneia interfered As discussed in (11), the young ages we
with the development or shape of Rheasilvia, find for these basins are consistent with the
as would have been expected during an impact preservation of the Vesta family’s steep size dis-
of binary objects (19). This indicates a minimum tribution (22, 23). Fugitive V-type asteroids take
formation interval of at least several hours, dur- ~1 billion years or more to migrate away from
ing which the putative second object would likely the family (21), so many could have originated
have missed Vesta (20). Thus, while Rheasilvia from Rheasilvia, or from an older large family–
and Veneneia are both relatively young impact populating impact event such as Veneneia.
features, they likely formed at different times. At least seven basins larger than 150 km have
The two large impact events at the south pole been identified on Vesta, including Rheasilvia
also excavated large amounts of rock that may and Veneneia (fig. S4) (11). Most of the thermal
have been the source of Vestoids and HEDs (1). alteration recorded in the argon-argon (Ar-Ar)
A provisional estimated minimum volume of ages of HED meteorites (24–26) may have oc-
excavated material at Rheasilvia based on the curred in thick slow-cooling units such as ejecta
observed concavity and the nominal volume of or basin floor deposits rather than directly dur-
Fig. 3. Dawn image mosaics showing ejecta of
the modeled transient excavation crater (15) is ing the impact events themselves (27), and Vesta’s
Rheasilvia basin. Each image was acquired at 62 m
resolution and show areas 35 km across. From top ~1 × 106 to 3 × 106 km3, or ~2 to 4% of the total surface may be a patchwork of basin-formed
to bottom, they show terrains with increasing de- volume of Vesta. Some Rheasilvia ejecta were units of distinct ages (11). The geologically re-
gree of mantling by ejecta in regions ~125 km, retained on the surface (Fig. 3), however. Ob- cent formation of Rheasilvia into at least two
75 km, and 50 km from the rim of Rheasilvia. literation of preexisting craters ≤20 km wide out preexisting large basins and their associated floor
to ~50 km from the rim implies ejecta thicknesses and ejecta deposits could have easily provided a
of order 4 to 5 km at this range, increasing to the ready source of large volumes of thermally al-
cratered, or obscured by Rheasilvia. A third older rim and decreasing outward to negligible thick- tered rocks with different resetting ages that could
basin ~250 km wide (5°N, 315°E) is also cross- ness north beyond a range of about 100 km. Mod- be launched to form the Vestoids and the HED
cut and heavily mantled by Rheasilvia (fig. eling of impact ejecta on Vesta (12) also predicts meteorite suite.
S4) (11). average thicknesses on this order.
Independent crater counts of Rheasilvia floor, Assuming an average ejecta thickness of 5 km References and Notes
1. P. C. Thomas et al., Science 277, 1492 (1997).
central massif, and proximal ejecta by three over a range of 100 km, we obtain a provisional 2. T. B. McCord, J. B. Adams, T. V. Johnson, Science 168,
different workers all converge on a relatively volume of ejecta on the surface Vesta of roughly 1445 (1970).
young crater retention and formation age for 5 × 105 km3 (15), suggesting that more than 3. G. J. Consolmagno, M. J. Drake, Geochim. Cosmochim.
Acta 41, 1271 (1977).
Rheasilvia on the order of 1.0 T 0.2 billion years half of Rheasilvia’s ejecta was lost to space, 4. J. Wisdom, Nature 315, 731 (1985).
(Fig. 4) (11). Crater counts also suggest a crater which is a relatively high fraction. The fraction 5. R. P. Binzel, S. Xu, Science 260, 186 (1993).
retention age for Veneneia of 2.1 T 0.2 billion lost to space is significantly more than the es- 6. C. T. Russell et al., Science 336, 684 (2012).
years (Fig. 4), predating Rheasilvia. Mantling timated <1 × 105 km3 volume of the Vesta family 7. The estimated depths for the basins are reported with
respect to the current reference ellipsoid shape of Vesta:
of Veneneia by Rheasilvia ejecta may allow for (21), which is consistent with the ejection into 285 by 229 km (6, 10). Otherwise, heights are reported
an older age, but the relatively intact rim topog- space of Rheasilvia ejecta to form the Vestoids. The with respect to local minimum and maximum elevations.
raphy of Veneneia suggests that it is not ancient. suggestion of a smaller second dynamical family The basin rim is defined here topographically and
696 11 MAY 2012 VOL 336 SCIENCE www.sciencemag.org
5. REPORTS
structurally by the inward facing scarp, arcuate ridge, 19. W. Bottke, H. J. Melosh, Icarus 124, 72 (1996). and the NASA Dawn at Vesta Participating Scientist
or break in slope. 20. If the formation time scale of Veneneia is a few hours, program for support. We thank the Dawn team for the
8. H. J. Melosh, Impact Cratering (Oxford Univ. Press, then to avoid interference with Rheasilvia a binary impactor development, cruise, orbital insertion, and operations
Oxford, 1989). would need a separation of at least ~3600 s × 5 km/s ~ of the Dawn spacecraft at Vesta. A portion of this
9. K. Keil, D. Stoffler, S. Love, E. Scott, Meteorit. Planet. Sci. 18,000 km or ~70 Vesta radii. The probability of both work was performed at the Jet Propulsion Laboratory,
32, 349 (1997). binary bodies hit Vesta would then be very small. California Institute of Technology, under contract
10. R. Jaumann et al., Science 336, 687 (2012). 21. D. Nesvorny et al., Icarus 193, 85 (2008). with NASA. Dawn data are archived with the NASA Planetary
11. S. Marchi et al., Science 336, 690 (2012). 22. F. Marzari, P. Farinella, D. R. Davis, Icarus 142, 63 (1999). Data System.
12. M. Jutzi, E. Asphaug, Geophys. Res. Lett. 38, L01102 (2011). 23. F. Marzari et al., Astron. Astrophys. 316, 248 (1996).
13. M. C. De Sanctis et al., Science 336, 697 (2012). 24. D. Bogard, Meteoritics 30, 244 (1995).
14. V. Reddy et al., Science 336, 700 (2012). 25. D. Bogard, D. Garrison, Meteorit. Planet. Sci. 38, 669 (2003). Supplementary Materials
www.sciencemag.org/cgi/content/full/336/6082/694/DC1
15. Materials and methods are available as supplementary 26. D. Bogard, Chem. Erde Geochem. 71, 207 (2011).
materials on Science Online. 27. Ar-Ar age resetting requires an extended time to diffuse Materials and Methods
16. B. Kriens, E. Shoemaker, K. Herkenhoff, J. Geophys. Res. Ar from the rocks; there is insufficient time to accomplish Supplementary Text
References (28, 29)
104, 18867 (1999). this in just the initial shock.
17. T. Kenkmann, Geology 30, 231 (2002).
18. P. Allemand, P. Thomas, J. Geophys. Res. 104, 16501 Acknowledgments: The authors thank D. Bogard, E. Asphaug, 12 April 2012; accepted 20 April 2012
(1999). and H. J. Melosh for helpful discussions and comments 10.1126/science.1223272
merous basaltic asteroids provide further support
Spectroscopic Characterization of for this hypothesis: Their orbits are distributed
Downloaded from www.sciencemag.org on May 10, 2012
from near Vesta to the 3:1 Kirkwood gap and
Mineralogy and Its Diversity the secular n-6 resonance that results in gravita-
tional perturbations. These, combined with colli-
Across Vesta sions, provide a convenient mechanism for their
delivery to Earth-crossing orbits (5–8).
Geochemical, petrologic, and geochronologic
M. C. De Sanctis,1* E. Ammannito,1 M. T. Capria,1 F. Tosi,1 F. Capaccioni,1 F. Zambon,1 studies of HEDs have led to the development
of models for the magmatic evolution of their
F. Carraro,1 S. Fonte,1 A. Frigeri,1 R. Jaumann,2 G. Magni,1 S. Marchi,3 T. B. McCord,4
parent body. The consensus is that the body was
L. A. McFadden,5 H. Y. McSween,6 D. W. Mittlefehldt,7 A. Nathues,8 E. Palomba,1
substantially melted early in its history through
C. M. Pieters,9 C. A. Raymond,10 C. T. Russell,11 M. J. Toplis,12 D. Turrini1
heating by decay of 26Al and 60Fe, forming a
molten core topped by a shell of molten silicates.
The mineralogy of Vesta, based on data obtained by the Dawn spacecraft’s visible and infrared Cooling and crystallization of a global magma
spectrometer, is consistent with howardite-eucrite-diogenite meteorites. There are considerable ocean could have produced an olivine-dominated
regional and local variations across the asteroid: Spectrally distinct regions include the south-polar mantle, a lower crust rich in low-Ca pyroxene
Rheasilvia basin, which displays a higher diogenitic component, and equatorial regions, which (diogenites), and an upper crust of basaltic flows
show a higher eucritic component. The lithologic distribution indicates a deeper diogenitic crust, and gabbroic intrusions (eucrites) (9, 10). How-
exposed after excavation by the impact that formed Rheasilvia, and an upper eucritic crust. ever, some HEDs are inconsistent with this sce-
Evidence for mineralogical stratigraphic layering is observed on crater walls and in ejecta. This is nario, leading to models involving less melting
broadly consistent with magma-ocean models, but spectral variability highlights local variations, and serial magmatism (11–14). The spatial dis-
which suggests that the crust can be a complex assemblage of eucritic basalts and pyroxene tribution of lithologies within the crust of the
cumulates. Overall, Vesta mineralogy indicates a complex magmatic evolution that led to a HED parent body would thus provide essential
differentiated crust and mantle.
elescopic visible and near-infrared spec- Fig. 1. (Top left) Spectra (nor-
T troscopy shows that the asteroid Vesta has
a basaltic surface dominated by the spec-
tral signature of pyroxene. Vesta spectra show
malized at 0.7 mm) of regions A
and B indicated in the VIR im-
age. (Top right) VIR color com-
many similarities to those of howardite-eucrite- posite (red = 0.92 mm, green =
diogenite (HED) meteorites (1), leading to the 0.62 mm, blue = 0.44 mm). Spa-
consensus that Vesta is differentiated and is the tial resolution is ~25 km. Arrow
parent body of the HED achondrites (2–4). Nu- indicates the south pole. (Bottom)
Average Vesta spectrum with
1
Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale T1 SD of the average. The data
di Astrofisica, Rome, Italy. 2Institute of Planetary Research, between 2.5 and 2.8 mm have
German Aerospace Center (DLR), Berlin, Germany. 3NASA Lunar been removed because they are
Science Institute, Boulder, CO, USA. 4Bear Fight Institute,
Winthrop, WA, USA. 5NASA, Goddard Space Flight Center,
not yet fully calibrated in this
Greenbelt, MD, USA. 6Department of Earth and Planetary region.
Sciences, University of Tennessee, Knoxville, TN, USA. 7NASA
Johnson Space Center, Houston, TX 77058, USA. 8Max-Planck-
Institut für Sonnensystemforschung, Katlenburg-Lindau, Ger-
many. 9Brown University, Providence, RI, USA. 10Jet Propulsion
Laboratory, California Institute of Technology, Pasadena, CA,
USA. 11Institute of Geophysics and Planetary Physics, University
of California, Los Angeles, CA, USA. 12Observatoire Midi-
Pyrenees, Toulouse, France.
*To whom correspondence should be addressed. E-mail:
mariacristina.desanctis@iaps.inaf.it
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