Planetary Vacuums, Atmospheres, & LifePaul H. Carr
While does our earth have a 21% Oxygen Atmosphere,
when our neighboring planets, Mars, and Venus, have mostly Carbon Dioxide?
Could our earth have a runaway greenhouse effect like Venus?
Is there life on the billions of exo-planets?
Why is the temperature of Venus hotter than Mercury that is closer to the sun.
Search for life in our (1) solar system and (2) Milky Way Galaxy
How life has and is now impacting our earth
The Viking labelled release experiment: life on Mars?Neil Saunders
This is a very old talk from around 1999 that I gave to my department at the Free University of Amsterdam. It\'s very out of date now, but still interesting.
Venusian Habitable Climate Scenarios: Modeling Venus Through Time and Applica...Sérgio Sacani
One popular view of Venus' climate history describes a world that has spent much of its life
with surface liquid water, plate tectonics, and a stable temperate climate. Part of the basis for this
optimistic scenario is the high deuterium to hydrogen ratio from the Pioneer Venus mission that was
interpreted to imply Venus had a shallow ocean's worth of water throughout much of its history. Another
view is that Venus had a long-lived (∼100 million years) primordial magma ocean with a CO2 and steam
atmosphere. Venus' long-lived steam atmosphere would sufficient time to dissociate most of the water
vapor, allow significant hydrogen escape, and oxidize the magma ocean. A third scenario is that Venus had
surface water and habitable conditions early in its history for a short period of time (<1 Gyr), but that a
moist/runaway greenhouse took effect because of a gradually warming Sun, leaving the planet desiccated
ever since. Using a general circulation model, we demonstrate the viability of the first scenario using the
few observational constraints available.We further speculate that large igneous provinces and the global
resurfacing hundreds of millions of years ago played key roles in ending the clement period in its history
and presenting the Venus we see today. The results have implications for what astronomers term “the
habitable zone,” and if Venus-like exoplanets exist with clement conditions akin to modern Earth, we
propose to place them in what we term the “optimistic Venus zone.”
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the Solar System is explored, including place where biology might exist.
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.
Might our earth undergo a runaway greenhouse warming similar to Venus?
Could there be life on the billions of exo-planets?
Why is the oxygen content of our earth’s atmosphere greater that of Venus and Mars, which are mostly CO2 ?
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
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.
Planetary Vacuums, Atmospheres, & LifePaul H. Carr
While does our earth have a 21% Oxygen Atmosphere,
when our neighboring planets, Mars, and Venus, have mostly Carbon Dioxide?
Could our earth have a runaway greenhouse effect like Venus?
Is there life on the billions of exo-planets?
Why is the temperature of Venus hotter than Mercury that is closer to the sun.
Search for life in our (1) solar system and (2) Milky Way Galaxy
How life has and is now impacting our earth
The Viking labelled release experiment: life on Mars?Neil Saunders
This is a very old talk from around 1999 that I gave to my department at the Free University of Amsterdam. It\'s very out of date now, but still interesting.
Venusian Habitable Climate Scenarios: Modeling Venus Through Time and Applica...Sérgio Sacani
One popular view of Venus' climate history describes a world that has spent much of its life
with surface liquid water, plate tectonics, and a stable temperate climate. Part of the basis for this
optimistic scenario is the high deuterium to hydrogen ratio from the Pioneer Venus mission that was
interpreted to imply Venus had a shallow ocean's worth of water throughout much of its history. Another
view is that Venus had a long-lived (∼100 million years) primordial magma ocean with a CO2 and steam
atmosphere. Venus' long-lived steam atmosphere would sufficient time to dissociate most of the water
vapor, allow significant hydrogen escape, and oxidize the magma ocean. A third scenario is that Venus had
surface water and habitable conditions early in its history for a short period of time (<1 Gyr), but that a
moist/runaway greenhouse took effect because of a gradually warming Sun, leaving the planet desiccated
ever since. Using a general circulation model, we demonstrate the viability of the first scenario using the
few observational constraints available.We further speculate that large igneous provinces and the global
resurfacing hundreds of millions of years ago played key roles in ending the clement period in its history
and presenting the Venus we see today. The results have implications for what astronomers term “the
habitable zone,” and if Venus-like exoplanets exist with clement conditions akin to modern Earth, we
propose to place them in what we term the “optimistic Venus zone.”
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the Solar System is explored, including place where biology might exist.
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.
Might our earth undergo a runaway greenhouse warming similar to Venus?
Could there be life on the billions of exo-planets?
Why is the oxygen content of our earth’s atmosphere greater that of Venus and Mars, which are mostly CO2 ?
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
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⊙)
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.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
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.
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...Neo4j
Leonard Jayamohan, Partner & Generative AI Lead, Deloitte
This keynote will reveal how Deloitte leverages Neo4j’s graph power for groundbreaking digital twin solutions, achieving a staggering 100x performance boost. Discover the essential role knowledge graphs play in successful generative AI implementations. Plus, get an exclusive look at an innovative Neo4j + Generative AI solution Deloitte is developing in-house.
Removing Uninteresting Bytes in Software FuzzingAftab Hussain
Imagine a world where software fuzzing, the process of mutating bytes in test seeds to uncover hidden and erroneous program behaviors, becomes faster and more effective. A lot depends on the initial seeds, which can significantly dictate the trajectory of a fuzzing campaign, particularly in terms of how long it takes to uncover interesting behaviour in your code. We introduce DIAR, a technique designed to speedup fuzzing campaigns by pinpointing and eliminating those uninteresting bytes in the seeds. Picture this: instead of wasting valuable resources on meaningless mutations in large, bloated seeds, DIAR removes the unnecessary bytes, streamlining the entire process.
In this work, we equipped AFL, a popular fuzzer, with DIAR and examined two critical Linux libraries -- Libxml's xmllint, a tool for parsing xml documents, and Binutil's readelf, an essential debugging and security analysis command-line tool used to display detailed information about ELF (Executable and Linkable Format). Our preliminary results show that AFL+DIAR does not only discover new paths more quickly but also achieves higher coverage overall. This work thus showcases how starting with lean and optimized seeds can lead to faster, more comprehensive fuzzing campaigns -- and DIAR helps you find such seeds.
- These are slides of the talk given at IEEE International Conference on Software Testing Verification and Validation Workshop, ICSTW 2022.
Goodbye Windows 11: Make Way for Nitrux Linux 3.5.0!SOFTTECHHUB
As the digital landscape continually evolves, operating systems play a critical role in shaping user experiences and productivity. The launch of Nitrux Linux 3.5.0 marks a significant milestone, offering a robust alternative to traditional systems such as Windows 11. This article delves into the essence of Nitrux Linux 3.5.0, exploring its unique features, advantages, and how it stands as a compelling choice for both casual users and tech enthusiasts.
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
In the rapidly evolving landscape of technologies, XML continues to play a vital role in structuring, storing, and transporting data across diverse systems. The recent advancements in artificial intelligence (AI) present new methodologies for enhancing XML development workflows, introducing efficiency, automation, and intelligent capabilities. This presentation will outline the scope and perspective of utilizing AI in XML development. The potential benefits and the possible pitfalls will be highlighted, providing a balanced view of the subject.
We will explore the capabilities of AI in understanding XML markup languages and autonomously creating structured XML content. Additionally, we will examine the capacity of AI to enrich plain text with appropriate XML markup. Practical examples and methodological guidelines will be provided to elucidate how AI can be effectively prompted to interpret and generate accurate XML markup.
Further emphasis will be placed on the role of AI in developing XSLT, or schemas such as XSD and Schematron. We will address the techniques and strategies adopted to create prompts for generating code, explaining code, or refactoring the code, and the results achieved.
The discussion will extend to how AI can be used to transform XML content. In particular, the focus will be on the use of AI XPath extension functions in XSLT, Schematron, Schematron Quick Fixes, or for XML content refactoring.
The presentation aims to deliver a comprehensive overview of AI usage in XML development, providing attendees with the necessary knowledge to make informed decisions. Whether you’re at the early stages of adopting AI or considering integrating it in advanced XML development, this presentation will cover all levels of expertise.
By highlighting the potential advantages and challenges of integrating AI with XML development tools and languages, the presentation seeks to inspire thoughtful conversation around the future of XML development. We’ll not only delve into the technical aspects of AI-powered XML development but also discuss practical implications and possible future directions.
Climate Impact of Software Testing at Nordic Testing DaysKari Kakkonen
My slides at Nordic Testing Days 6.6.2024
Climate impact / sustainability of software testing discussed on the talk. ICT and testing must carry their part of global responsibility to help with the climat warming. We can minimize the carbon footprint but we can also have a carbon handprint, a positive impact on the climate. Quality characteristics can be added with sustainability, and then measured continuously. Test environments can be used less, and in smaller scale and on demand. Test techniques can be used in optimizing or minimizing number of tests. Test automation can be used to speed up testing.
Enchancing adoption of Open Source Libraries. A case study on Albumentations.AIVladimir Iglovikov, Ph.D.
Presented by Vladimir Iglovikov:
- https://www.linkedin.com/in/iglovikov/
- https://x.com/viglovikov
- https://www.instagram.com/ternaus/
This presentation delves into the journey of Albumentations.ai, a highly successful open-source library for data augmentation.
Created out of a necessity for superior performance in Kaggle competitions, Albumentations has grown to become a widely used tool among data scientists and machine learning practitioners.
This case study covers various aspects, including:
People: The contributors and community that have supported Albumentations.
Metrics: The success indicators such as downloads, daily active users, GitHub stars, and financial contributions.
Challenges: The hurdles in monetizing open-source projects and measuring user engagement.
Development Practices: Best practices for creating, maintaining, and scaling open-source libraries, including code hygiene, CI/CD, and fast iteration.
Community Building: Strategies for making adoption easy, iterating quickly, and fostering a vibrant, engaged community.
Marketing: Both online and offline marketing tactics, focusing on real, impactful interactions and collaborations.
Mental Health: Maintaining balance and not feeling pressured by user demands.
Key insights include the importance of automation, making the adoption process seamless, and leveraging offline interactions for marketing. The presentation also emphasizes the need for continuous small improvements and building a friendly, inclusive community that contributes to the project's growth.
Vladimir Iglovikov brings his extensive experience as a Kaggle Grandmaster, ex-Staff ML Engineer at Lyft, sharing valuable lessons and practical advice for anyone looking to enhance the adoption of their open-source projects.
Explore more about Albumentations and join the community at:
GitHub: https://github.com/albumentations-team/albumentations
Website: https://albumentations.ai/
LinkedIn: https://www.linkedin.com/company/100504475
Twitter: https://x.com/albumentations
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
Maruthi Prithivirajan, Head of ASEAN & IN Solution Architecture, Neo4j
Get an inside look at the latest Neo4j innovations that enable relationship-driven intelligence at scale. Learn more about the newest cloud integrations and product enhancements that make Neo4j an essential choice for developers building apps with interconnected data and generative AI.
Sudheer Mechineni, Head of Application Frameworks, Standard Chartered Bank
Discover how Standard Chartered Bank harnessed the power of Neo4j to transform complex data access challenges into a dynamic, scalable graph database solution. This keynote will cover their journey from initial adoption to deploying a fully automated, enterprise-grade causal cluster, highlighting key strategies for modelling organisational changes and ensuring robust disaster recovery. Learn how these innovations have not only enhanced Standard Chartered Bank’s data infrastructure but also positioned them as pioneers in the banking sector’s adoption of graph technology.
1. Planetary Ecosynthesis on Mars: Restoration Ecology and Environmental Ethics
Christopher P. McKay
NASA Ames Research Center
Revised December 2007
1. Introduction
There has been a lively discussion recently about the science and ethics of
“terraforming” Mars. The high level of interest is a result of spacecraft discoveries about
Mars combined with the realization that humans are effectively warming the Earth and
wondering if they can, and should, do the same on Mars. I suggest that terraforming is
more appropriately called planetary ecosynthesis, and in this Chapter I review the
scientific studies of planetary ecosynthesis and the environmental ethics associated with
instigating such global change on another planet.
Mars today is a cold, dry, frozen desert world on which not even the most hardy
of Earth life could survive. Temperatures average -60oC and the pressure averages 0.6
kPa, over one hundred times less than atmospheric pressure at the surface of the Earth.
As a result of the low pressure, and secondarily the low temperature, water is not liquid
on the surface of Mars at any location or season. Strong solar ultraviolet radiation reaches
the surface of Mars to complete the deadly mix of hostile environmental conditions.
But Mars has not always been this harsh. There is compelling evidence that early
in its history Mars had stable liquid water on its surface [1, 2]. Presumably this phase of
liquid water was associated with a higher pressure and somewhat warmer atmosphere.
This evidence for liquid water on Mars – originally from the Mariner 9 and Viking
missions and now confirmed by recent missions – is the central motivation for the search
for past life on Mars (e.g.[3, 4]).
The fact that Mars once supported widespread liquid water and possibly life on
its’ surface opens the question of the feasibility of restoring such conditions on Mars by
artificial means. The fundamental challenge of restoring habitable conditions on Mars is
to warm up the planet from its current -60oC to over 0oC, and perhaps as warm as +15oC
– reaching parity with Earth. Humans have demonstrated, and implemented, the
technology to warm planets with Earth as our first target. The level of human-induced
warming on Earth is debated but is probably on the order of a few degrees. On Mars the
warming needed would be tens of degrees – a hundred times larger than on Earth – but
the extrapolation from Earth to Mars is conceptually straightforward. Energy balance
calculations suggest that warming Mars might be achieved in 100 years or less [5, 6].
Producing an oxygen rich atmosphere would take more than 100,000 years. Thus,
warming Mars is within current technology and this fact frames the discussion about
Mars in a fundamentally different way than planetary scale environmental alteration on
any other world of the Solar System. Because the question of “can we” has been
tentatively answered for Mars in the affirmative, the question of “should we” and “will
we” warrant consideration.
The scientific issues associated with planetary ecosysnthesis on Mars have been
discussed in the scientific literature for decades. Initial discussions were limited [7-10]
2. 2
until “Making Mars Habitable” was featured on the cover of Nature magazine and the
field was rightly considered to have entered mainstream scientific discussion [5]. There
are currently two international science journals, Astrobiology and the International
Journal of Astrobiology that explicitly consider planetary ecosynthesis as part of their
content.
2. Conditions needed for habitability
The first step in considering ecosynthesis on Mars is the delineation of the
requirements for habitability. We tend to think of the present Earth as the only model for
a habitable world. However, there are two alternative possibilities for life supporting
states for Mars, one with oxygen and one without. These two alternative states are listed
in Table 1, adapted from McKay et al. [5]. Life could survive on Mars in an atmosphere
composed of carbon dioxide with moderate levels of nitrogen and low levels of oxygen.
Such an atmosphere is thought to have prevailed on Earth before the rise of oxygen 2 Gyr
ago. It is also the likely composition of a thick early atmosphere on Mars. Many bacteria,
some plants and even a few animals can survive in low oxygen atmospheres. Humans
would require a source of oxygen and could not breath the high carbon dioxide.
A second habitable state to consider is an oxygen-rich atmosphere that is
essentially the same as on the present Earth. As we discuss below it appears feasible to
create a habitable state on Mars based on a carbon dioxide rich atmosphere but it is not
feasible to create an oxygen-rich atmosphere.
Table 1. Habitability (adapted from McKay et al. [5]).
Parameter Limits Note
Global temperature 0°C - 30°C Earth = 15°C
Composition for plants, algae, microorganisms
Total pressure > 1 kPa Water vapor pressure plus O2, N2, CO2
CO2 >0.015 kPa Lower limit set by photosynthesis
No clear upper limit
N2 >0.1 - 1 kPa Nitrogen fixation
O2 >0.1 kPa Plant respiration
Composition for breathable air
Total pressure:
Pure O2 > 25 kPa Lung water vapor plus CO2, O2
Air mixture > 50 kPa Based upon high elevation
< 500 kPa Buffer gas narcosis
CO2 < 1 kPa Set by toxicity
N2 > 30 kPa Buffer gas
O2 > 13 kPa Lower limit set by hypoxia
< 30 kPa Upper limit set by flammability
Figure 1. Liquid water in the past on Mars. Mars Global Surveyor image showing Nanedi
vallis in the Xanthe Terra region of Mars. Image covers an area 9.8 km by 18.5 km; the
canyon is about 2.5 km wide. This image is the best evidence we have that some of the
fluvial features on Mars were carved by liquid water in stable flow on the surface for an
extended interval. Photo from NASA/Malin Space Sciences.
3. 3
3. What went wrong with Mars?
There is compelling evidence that Mars had more habitable conditions in the past.
However, it is not clear what happened to the atmosphere and hydrosphere of early Mars.
It is generally thought that Mars lost its carbon dioxide atmosphere through a
combination of processes all related to its small size (Mars is 1/10 the mass of the Earth,
Mars and Earth are compared in Table 2). These processes include the formation of
carbonates, loss to space due to solar wind sputtering, and atmospheric erosion due to
impacts of comets and asteroids. The relative importance of these processes is debated
(see, e.g. [11]) but these processes all occur on Earth as well. They are more pronounced
on Mars because it is so much smaller than the Earth.
Earth is large enough that its internal heat flow can drive plate tectonics. Mars has
a single thick plate. As a result Mars does not have the recycling of material that results
from the subduction of one plate under another and the ejection of gases in the resulting
arc volcanoes. The gases emitted from arc volcanoes such as Mt. St. Helens in the
Cascade Range represent the recycling of material into the atmosphere by plate tectonics.
Mars is too small to have plate tectonics and hence has no way to recycle materials such
as carbonates. The lack of recycling and high loss rates due to lower gravity and no
magnetic field are thought to be responsible for the loss of most of the carbon dioxide of
the early martian atmosphere. The amount of CO2 still present on Mars is unknown.
Table 2. Comparison of Mars and Earth.
Parameter Mars Earth
Mass 0.107 1
Surface pressure 0.5 to 1 kPa 101.3 kPa
Average temperature -60oC +15oC
Temperature range -120oC to +25oC -80oC to +50oC
Atmosphere composition 95% CO2 78% N2
2.7% N2 21% O2
1.6% Ar 1% Ar
Incident sunlight 149 W m-2 344 W m-2
Surface gravity 3.73 m s-2 9.80 m s-2
Solar day 24h 39m 35.238s (“sol”) 24 h
Sidereal year 687 days, 668.6 sols 365.26 days
Obliquity of axis 25 deg 23.5 deg
Eccentricity 0.0934 0.0167
Mean distance to sun 1.52 AU 1 AU (1.49x108 km)
Figure 2. Warming of Mars due to simple fluorine-based gas independently and the best
gases combination (dashed line) for the given total greenhouse gas amounts (PCO2 = 0.6
kPa) from Marinova et al. (2005).
There may have also been some loss of the initial water on Mars but a large part
of it is still present on Mars --- frozen into the ground in the polar regions. Based on the
morphology of the craters in the polar regions of Mars, it was deduced that the ground
there is rich in ice [12]. Direct confirmation came from the gamma ray and neutron
detectors on the Mars Odyssey mission which indicated the presence of ice-rich ground
in the upper two meters for latitudes poleward of about 60o in both hemispheres [13].
4. 4
Radar results indicate that this ice-rich ground extends down to 2 km or more in the
northern hemisphere [14]. A veritable frozen ocean of water is still present on Mars.
The factors that resulted in Mars’ loss of habitability are related to its small size
and resulting lack of plate tectonics. These are not factors that can be changed with
foreseeable technologies. Therefore, one possible objection to ecosynthesis on Mars is
that it would be doomed to fail over geological time due to the same factors that doomed
an initial habitable environment on Mars. The logic of this argument is correct: Mars’
newly restored to habitability would only have a finite lifetime. This lifetime would be
approximately given by the timescale of the removal of the atmosphere due to carbonate
formation, about 10 to 100 million years. This is a short time compared to the age of
Mars – 4.5 billion years – but a long time compared to human timescales. It is relevant
here to note that Earth will not remain habitable much longer than this timescale. Current
estimates suggest that Earth will become uninhabitable in 500 million years or less as it
becomes become Venus-like due to the progressive brightening of the Sun [15]. Thus, a
habitable Mars that persists for 10 to 100 million years is “Earth-like” in terms of its life
expectancy. No solutions for infinite lifetime exist for Mars or Earth. Nothing lasts
forever, not even the Earth and sky [16].
As discussed above, it appears certain that Mars still has a vast amount of water,
albeit frozen in the ground. The total CO2 amount on Mars, as carbonate, absorbed gas in
the soil, or frozen in the polar caps is unknown. There is only about 0.6 kPa of CO2 in
the atmosphere at the present time but estimates of the total CO2 in the soil, atmosphere
and cap range from as low as a few kPa to as high as 100 kPa [17].
A biosphere requires large amounts of CO2 and H2O but also N2. Nitrogen gas is
essential for a breathable atmosphere (see Table 1) and nitrogen is needed by life as an
essential macronutrient. The only known supply of nitrogen on Mars is in the
atmosphere at a level of 0.016 kPa, a tiny amount compared to the 80 kPa of N2 in Earth’s
atmosphere. If this nitrogen were entirely converted to biological material it would only
form a layer only 1 cm thick. Mars cannot support a biosphere if the current atmospheric
N2 is the total nitrogen available on the planet. Unfortunately, there is no data on the
amount of nitrogen in the soil of Mars as nitrate. Theoretical arguments suggest that
lightning and meteorites should have produced nitrates on Mars and there may be up to
30 kPa present [17,18]. The question of the nitrogen supply is probably the key question
in terms of the feasibility of ecosynthesis on Mars using near-term technologies.
Mars does not have a planetary magnetic field but probably does not need one to
be habitable. There are two primary reasons that a magnetic field is sometimes proposed
as required for habitability 1) to provide shielding against radiation and 2) to prevent
solar wind erosion of a thick martian atmosphere.
4. Radiation protection
The Earth's magnetic field does not deflect galactic cosmic rays because these
particles are much too energetic. These particles are primarily stopped by the mass of the
Earth's atmosphere which is equivalent to 1 kg cm-2. The Earth's magnetic field does
deflect solar protons, channeling these particles to the polar regions creating the aurora.
However, even without the magnetic field these particles would not penetrate the Earth's
atmosphere and would not reach the surface.
5. 5
If Mars had an Earth-like surface pressure of 1 atm, its atmospheric mass would
be 2.6 kg cm-2 due to the lower gravity (to reach the same surface pressure with a lower
gravity, 0.38 g, requires a more massive atmosphere). Thus, the radiation shielding
effects of the martian atmosphere would exceed those for the Earth and a magnetic field
is not essential for radiation protection. Furthermore, Earth occasionally loses its strong
dipole field during field reversals. These events are not correlated with any increases in
extinctions in the fossil record.
5. Atmospheric erosion
Because Mars (and Venus) do not have magnetic fields, the solar wind impacts
directly on the upper atmospheres of these planets. This does result in a small rate of
atmospheric loss at the present time. However, the loss rate would not increase if we
increased the surface pressure of the martian atmosphere. This is due to the fact that
conditions at the top of a thicker atmosphere would be similar to the conditions at the top
of the present atmosphere only raised by a small elevation. For example, if the surface
pressure on Mars were to increase to one atmosphere, the low pressure regions of the
atmosphere would be raised in altitude. We can estimate the height change by computing
the scale height in a warm Earth-like martian atmosphere (Because scale height is inverse
with gravity and Mars’ gravity is 0.38 times Earth, and inverse with mean molecular
weight; Mars 44, Earth 29, the scale height on Mars would be 14 km, compared to 8 km
on Earth). To increase the pressure on Mars from 0.6 kPa to 100 kPa requires a pressure
increase of 166 or 5.1 scale heights (e5.1 = 164) resulting in an altitude gain of 71 km for
the upper atmosphere. This is a tiny increment compared to the radius of the planet.
Thus, the top of the atmosphere would feel essentially the same gravity as it does today
and would feel the solar wind at the same intensity. The net result is that the erosion of
gases from the martian atmosphere by the solar wind would remain unchanged. The
current loss rate is not significant; for example the loss rate of water on Mars today
corresponds to the loss of a layer of water two meters thick over 4 billion years (e.g.
[19]).
6. Energy and time requirements
The discussion above shows that the necessary materials to construct a biosphere
are likely to be present on Mars and that in addition the fundamental physical aspects of
Mars that would be virtually impossible to alter such as axial tilt, rotation rate, and
eccentricity, are similar to the corresponding values for Earth (see Table 2). The one
exception is the surface gravity, which is 0.38 of the Earth value. It is typically assumed
that life from Earth can accommodate this lower gravity but this has not yet been tested.
If the physical materials are present, the next question in determining the
feasibility of planetary ecosynthesis on Mars is to compute the energy and time required
to affect the desired change. The problem naturally divides into two phases [5, 6]. Phase
1 is warming Mars from the present cold state and restoring the thick atmosphere of CO2.
Phase 2 is the production of O2 in sufficient quantities to be breathable by humans. The
energy requirements of each phase are listed in Table 3 and are also expressed in terms of
the sunlight incident on Mars. Trapping and using sunlight is the only plausible energy
6. 6
source for changing the environment on a global scale. From Table 3 we can see that if
the sunlight incident on Mars could be utilized with 100% efficiency it would take only
~10 years to warm Mars and restore the thick CO2 atmosphere. Clearly 100% efficiency
is an overestimate but atmospheric supergreenhouse gases, as discussed in the next
section, can effectively alter the energy balance of a planet and efficiencies of 10% are
plausible. Thus, the timescale for warming Mars is ~100 years.
Table 3. Energy Requirements for Terraforming Mars
Initial State Final State Amount Energy Solar Energya Time
[J m-2] [years] [years]
Surface Warming
CO2(s) at 125°C CO2(g) at 15°C 200 kPa; 5.4x104 kg m-2 3.7x1010 7.9
Dirt at -60°C Dirt at 15°C ~10 m; 2x104 kg m-2 1.2x109 0.3
H2O(s) at -60°C H2O(l) at 15°C 10 m; 1x104 kg m-2 5.5x109 1.2
H2O(s) at -60°C H2O(g) at 15°C 2 kPa; 5.4x102 kg m-2 1.6x109 0.33
Total: 10 100
Deep Warming
H2O(s) at -60°C H2O(l) at 15°C 500 m; 5x105 kg m-2 2.8x1011 56 500
Making O2
CO2(g) + H2O CH2O + O2(g) 20 kPa; 5.4x103 kg m-2 8x1010 17 100000
a 9 -2 -1
Energy divided by the total solar energy reaching Mars in a year, 4.68x10 J m yr
Adapted from McKay et al. [5].
To produce a level of breathable O2 from CO2 on Mars would require the energy
equivalent of 17 years of Martian sunlight. While the energy level here is comparable to
the energy to warm Mars, the efficiency is much lower. Because of basic thermodynamic
constraints, the efficiencies for warming are much higher than the efficiencies for causing
chemical reactions. Sunlight will not spontaneously produce O2 from CO2: a mechanism
to drive the reaction is required. The only known mechanism that can operate on a global
scale and use sunlight to convert CO2 to O2 is a biosphere. This conversion is precisely
the reaction that produces biomass in the Earth’s biosphere. Given that the Earth has an
extensive biosphere that has been utilizing this reaction for billions of years, the
efficiency of the Earth’s biosphere is a plausible upper limit to the efficiency of a Martian
biosphere. The production of biomass on Earth corresponds to the energy equivalent of
0.01% of the energy incident on the Earth as sunlight. Assuming this optimistic
efficiency it would take over 100,000 years to produce the minimal breathable O2 levels
on Mars as defined in Table 1. Clearly this efficiency for Earth is an average over all of
the Earth’s biomes with widely different individual efficiencies, from dry deserts to lush
rain forests. If a planet could be entirely covered with rain forests then clearly the
efficiency would go up, maybe as much as a factor of 10. However, a global biosphere
on Mars is likely to have a range of ecosystems just as does the Earth. The long
timescale indicated by this calculation is not a precise prediction but it is a robust
indicator that producing a breathable O2 atmosphere on Mars will take many thousands,
or hundreds of thousands, of years.
Energetic considerations indicate that warming Mars and restoring a thick CO2
atmosphere could be accomplished over human timescales (~100 years). Altering the
7. 7
atmosphere to make it breathable to humans (~20% O2) is not possible with present
technologies for all intents and purposes.
7. Warming Mars
There have been many proposed methods for warming Mars (see [20]) but the
only one that is clearly rooted in demonstrated technology is based on supergreenhouse
gases. Originally suggested by Lovelock and Allaby [21] and worked out in detail by
Marinova et al. [22] the basic idea is to use supergreenhouse gases to increase the
greenhouse effect on Mars. Marinova et al [22] considered the production on Mars of
supergreenhouse gases composed only of F, S, C and H. Supergreenhouse gases
containing Cl and Br were specifically excluded from consideration because of the
deleterious effect these chemical species have on ozone. Climate calculations have shown
that if there is CO2 ice present in the polar regions of Mars, then a warming of 20oC will
cause the complete evaporation of that ice through a positive feedback mechanism [5,
21]. The results of the atmospheric energy balance calculations of Marinonva et al. [22]
indicate that the production of fluorine-based gases at levels of 0.1 to 1 Pa is a possible
way to increase the mean Mars temperature to the levels necessary to cause the
outgassing and evaporation of all available CO2 ice on Mars. Figure 2 shows the
temperature increase for the present Mars for several gases. Of the gases considered, C3F8
was the most potent artificial greenhouse gas for use on the present Mars. Less than 1 Pa
of C3F8 (a few ppm in an Earth-like atmosphere) would result in sufficient warming of
Mars to cause complete CO2 outgassing.
Releasing CO2 is a key step in warming Mars because CO2 contributes to the
greenhouse effect and thus a positive feedback on further CO2 release. Furthermore, CO2
is the most readily available gas on Mars to bring the pressure up high enough that liquid
water can be stable.
8. Ethics
In the previous sections I have briefly summarized the state of our scientific
understanding of the possibilities of planetary ecosynthesis on Mars. More detailed
reviews can be found in McKay et al. [5], Fogg [20], Marinova et al. [22] and Graham
[23]. I suggest the following conclusions based on the scientific literature:
1. It is likely that Mars has adequate amounts of CO2, H2O, and N2 for the
construction of a biosphere.
2. The timescale for warming Mars and restoring a thick CO2 atmosphere is
relatively short (~100 years). However, it is not practical to create a breathable
(~20% O2) atmosphere on Mars.
3. If restored to habitability Mars would maintain its habitable state for 10 to 100
million years.
4. Supergreenhouse gases based on F, S, C and H could be produced on Mars and
used to warm the planet. Human-produced supergreenhouse gases are currently
8. 8
warming the Earth. Concentrations 100 to 1000 times higher than the
anthropogenic levels in Earth’s atmosphere are needed on Mars.
5. The scientific community considers planetary ecosynthesis on Mars as a serious
topic in space research.
The fact that we are altering the Earth’s global climate and the possibility that
using the same methods we “can” alter the habitability of Mars implies that the question
of “should” we conduct planetary ecosynthesis is a timely and relevant one. The
environmental ethics of planetary ecosynthesis on Mars is therefore a subject for
consideration and in the rest of the chapter I provide some preliminary observations.
Environmental ethics has developed on Earth and mostly in response to
environmental crises. It is perhaps not surprising that extrapolating environmental ethics
to an apparently lifeless world is not straightforward. The universal yet unexamined
assumption of environmental ethics is that nature is equivalent to life. On Earth this
equivalence is obviously true. No aspect of the environment on Earth can be considered
separate from biological effects. Most systems of environmental ethics have not
attempted to make any meaningful distinction between nature and life. Consider as an
example the “Land Ethic” articulated by Aldo Leopold [24]. “A thing is right when it
tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong
when it tends otherwise.” As I have discussed before [25]) it is unclear how to apply this
to Mars. Indeed as we leave the Earth we see that the equivalence of life and nature is, as
far as we now know, only applicable to Earth. Everywhere else in our Solar System we
encounter nature that is profoundly devoid of life. The fundamental challenge in
applying environmental ethics beyond the Earth is to delve one level deeper than has
been necessary on Earth and examine the difference between the environmental ethics of
nature and the environmental ethics of life.
I have argued ([25]) that to understand the difference between nature and life in a
system of environmental ethics requires a clarification of the fundamental assumptions –
the normative axioms – on which the system is based. Systems of environmental ethics
are based on varying combinations of three normative axioms which I identify as
1. Preservationism. The fundamental principle that nature is not to be altered by
human beings.
2. Wise stewardship. The fundamental principle that the measure of all things is
utility to humans, in the broadest and wisest sense of utility.
3. Intrinsic worth. The fundamental principle that there exist sets of objects which
have intrinsic worth regardless of their instrumental value to humans.
These are principles on which systems of environmental ethics are based and not
categories into which systems of environmental ethics are grouped. Furthermore, they are
not mutually exclusive. Indeed, virtually all systems of environmental ethics are based
on some combination of these principles in varying degrees. Anti-humanism as
expressed by Ehrenfeld [26] is an extreme form of preservationism in which all human
9. 9
actions are to be suppressed. Anti-humanism was the original label used by McKay [25].
Rolston [27] and Hargrove [28] provide a more balanced view of preservationism and
suggest the term now used here.
Wise stewardship is certainly the most common and influential fundamental
principle in environmental ethics. It is so pervasive that it is often assumed without
statement. The most common argument in environmental ethics is that we humans
jeopardize our own interests when we degrade the environment.
The third fundamental principle listed above is relatively recent and not fully
developed in the environmental ethics literature. The principle of intrinsic worth posits
that there are sets of objects which have value of themselves independent of any
instrumental or intellectual utility to other beings. The principle itself has wide
adherence if the set of intrinsic objects is restricted to human beings. Historically the
restrictions were more severe, but over time the sphere of consideration has expanded
along the dimensions of race, gender, disability, and ethnicity so that now virtually
everyone would agree that all humans are in the set of objects with intrinsic worth. There
have been serious arguments presented to expand the sphere of consideration to non-
human animals [29] to ecosystems [30] and to all life itself [31, 32]. In all cases the
discussion has been in the context of life forms of intrinsic worth pre-existing within the
state of nature. No choice between nature and life forms of intrinsic worth has been
considered. However, this is just the choice we face on Mars. The state of nature is
lifeless and we have before us a choice to replace that state with a state with life forms of
intrinsic worth. If richness and diversity in life forms is a value in itself, then planetary
ecosynthesis on Mars is a good thing.
9. Utilitarian motivations for planetary ecosynthesis on Mars
Given the importance of the utilitarian principle in environmental ethics it is
instructive to consider how planetary ecosynthesis on Mars is – or is not useful – to
humans.
Mars is not useful as a “lifeboat” to which humanity flees after having destroyed
the Earth. This is a common idea in science fiction but has no technical basis. Past
migrations of people have occurred in which a significant fraction of the population
relocates over a great distance. An example is the Irish migration to North America.
However, this example does not hold for space travel. Any foreseeable technology for
space travel involves only a very small number of travelers.
The advantages of a small number of humans and assorted life forms from Earth
present on Mars as a genetic “Noah’s ark” are dubious as well. There are certainly
possible scenarios, such as a large asteroid strike or unchecked plague, in which large
fractions of the human population on Earth are killed, but even if the survival rate on
Earth was one in a million the residual population would be huge compared to any
plausible population on Mars. Events that could literally sterilize the Earth – such as a
nearby supernova and the sun entering the red giant stage – would also sterilize Mars.
Finally the idea that a human colony present on Mars or the prospect of making
Mars habitable would allow us, or cause us, to disregard environmental principles on
Earth is absurd.
10. 10
A more plausible utilitarian value that can be obtained from planetary
ecosynthesis on Mars is the knowledge that we, human society, would derive from such
activities. Humans have global effect on the environment of Earth and our effects are
growing as our population and technology increase. It is therefore inevitable that humans
will assume some management responsibility for the Earth’s environment. The view that
the environment is self regulating and does not require human intervention is not tenable
if humans continue to have such a growing impact. Understanding the Earth well enough
to manage it is a daunting task. Clearly the knowledge needed for this task will primarily
be obtained from studies of the Earth itself. However, studies of other planets can
provide important comparison points and context for the Earth. Along these lines, studies
of planetary ecosynthesis on Mars could provide important lessons as to how a biosphere
can work. The words left on Richard Feynman’s blackboard on his last day of work
“What I cannot create I do not understand” expresses this point. An essential task in
understanding, and managing the biosphere on Earth, may be the creation of a biosphere
on Mars.
The potential knowledge to be gained by studying ecology on Mars is greatly
increased if Mars has indigenous life that represents a separate origin from life on Earth
[33]. Throughout this discussion I have assumed that Mars is a lifeless planet. However,
it is possible that Mars has life either in secluded habitable zones or frozen dormant in the
polar ices. If there is life on Mars, or was life, it may share a common origin with life on
Earth or it may represent an independent origin of life. As recently as a decade ago it
was assumed that if there was life on Mars it would have to represent an independent
origin since it was present on a different planet. However, we now know that rocks from
Mars have reached Earth intact and furthermore that the temperatures in these rocks
would not reach sterilizing levels during the trip [34]. These rocks are the result of
impacts on Mars ejecting material into space. Early in the history of the Solar System the
impact, and hence transfer rate, would have been much higher. Thus, life from Mars
could have been carried to Earth inside one of these rocks. Presumably the converse is
also true – rocks from Earth could have carried life from Earth to Mars. Because of this
interplanetary rock transfer it is no longer assumed that life on Mars would necessarily be
of a separate origin. Indeed most researchers would consider that the most likely case
would be a common origin for life on Earth and Mars and convincing evidence to the
contrary would be required before it was concluded that Mars had an independent origin
of life.
If there has never been life on Mars then there are minimal implications for
planetary ecosynthesis. If there was life on Mars and it is now extinct beyond recovery,
then planetary ecosynthesis can be viewed as a type of “restoration ecology”. If there is
life on Mars, or recoverable life, but it shares a common ancestor with life on Earth then
it seems plausible that planetary ecosynthesis can proceed using Earth life forms as
needed.
Perhaps the most interesting and challenging case is that in which Mars has, or
had, life and this life represents a distinct and second genesis [35, 36]. The discovery of a
second genesis of life has profound scientific, as well as philosophical and ethical
importance. Philosophically, the discovery would directly address the question of life in
the universe, and would strongly support the idea that life is a naturally emergent
phenomenon and is widespread and diverse in the universe. Scientifically, having another
11. 11
example of life expands the scope of biology from one to two. There may well be
significant advances in medicine, agriculture, pest control, and many other fields of
biological inquiry, from having a second type of life to study. I would argue that if there
is a second genesis of life on Mars, its enormous potential for practical benefit to humans
in terms of knowledge should motivate us to preserve it and to enhance conditions for its
growth. Observations of Mars show that currently there is no global biosphere on that
planet and if life is present it is in isolated refugia or dormant. It is possible that life
present on Mars today is at risk of extinction if we do not alter the Martian environment
so as to enhance its global habitability.
An appreciation for the potential utility and value of the restoration of a Martian
biota does not depend on the assignment of intrinsic value to alternative lifeforms. The
creation of a second biosphere using a second genesis of life could be of great utilitarian
value for humans in terms of the knowledge derived ranging from basic biology to global
ecology. And a case can be made [35] that its’ value exceeds the opportunity cost of not
establishing human settlements on Mars.
The utilitarian arguments presented above indicate that we should alter Mars to
allow any indigenous life to expand and form a global biosphere even if the resulting
biosphere is never a natural home for life from Earth or humans. If there is no indigenous
life, these utilitarian arguments indicate that we should alter Mars to support life from
Earth even if this never results in a biosphere that can be a natural home for humans. The
point is only a theoretical one since our current understanding of Mars and planetary
physics suggests that it is not possible using foreseeable technology to make Mars into a
world that can be an Earth-like home for humans. Humans would require some sort of O2
source to move around the planet – a significant improvement in habitability compared to
the current state.
This discussion has implications for near-term exploration of Mars by robots and
humans. Until we know the nature life on Mars and its relationship – if any – to life on
Earth, we must explore Mars in a way that keeps our options open with respect to future
life. I have argued elsewhere [36] that this means that we must explore Mars in a way
that is biologically reversible. Exploration is biologically reversible if it is possible and
practical to remove all life forms carried to Mars by that exploration. Because of the high
UV and oxidizing conditions on Mars, biological reversibility is achievable. Previous
missions to Mars, such as the Pathfinder mission and the two MER rovers, have carried
microorganisms to the martian surface where they remain dormant as long as shielded
from ultraviolet radiation. To reverse this contamination already present on Mars, it
would be necessary to collect all metal objects within which microbes could remain
viable. Furthermore, the soil at crash sites and in the vicinity of landers that had come
into contact with the spacecraft would have to be thrown up into the atmosphere where it
would be exposed to sterilizing ultraviolet radiation. A similar approach can be used to
reverse the contamination from human bases.
10. Summary
Planetary ecosynthesis on Mars is being seriously discussed within the field of
planetary science. It appears that restoring a thick atmosphere on Mars and the recreation
of an environment habitable to many forms of life is possible. It is important now to
12. 12
consider if it “should” be done. To do this takes us into new and interesting territory in
environmental ethics but both utilitarian and intrinsic worth arguments support the notion
of planetary ecosynthesis. Strict preservationism arguments do not. It is important to
have the long-term view of life on Mars and the possibilities of planetary ecosynthesis.
This affects how we explore Mars now. Mars may well be our first step out into the
biological universe, it is a step we should take carefully.
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Figure 1. Liquid water in the past on Mars. Mars Global Surveyor image showing Nanedi
vallis in the Xanthe Terra region of Mars. Image covers an area 9.8 km by 18.5 km; the
canyon is about 2.5 km wide. This image is the best evidence we have that some of the
fluvial features on Mars were carved by liquid water in stable flow on the surface for an
extended interval. Photo from NASA/Malin Space Sciences.
15. 15
Figure 2. Warming of Mars due to simple fluorine-based gas independently and the best
gases combination (dashed line) for the given total greenhouse gas amounts (PCO2 = 0.6
kPa) from Marinova et al. (2005).