self-portrait of NASA's Curiosity Mars rover
By NASA - http://photojournal.jpl.nasa.gov/catalog/PIA19920, Public Domain, Link
The Middle Eastern Bronze Age pastoralists who made up the Hebrew creation myths that later found themselves bound up in a book declared to be the inerrant word of a god, were probably aware of the planet Mars.
Certainly, the Sumerians, Egyptians, Greeks and Romans were and even named it after one of their gods - Nergal, Her Dashur, Ares and Mars, respectively. Because of its red colour, it was associated with blood and, by extension, war and violence.
But of course, the authors of Genesis thought it was stuck to the dome over their small flat planet, so they assumed it was made during 'Creation Week' and so had as little knowledge of its history as they had of their own planet - i.e., none at all. Had they realised Mars had water forming oceans, lakes and rivers 3 billion years earlier (they didn't even have a word for a number so large), they could have made up a slightly more plausible creation myth, at least as far as a time-scale is concerned.
But of course, as a small red light stuck to the dome, they had no more idea than fly how it got there, why it looked red or what it could tell them about planetary orbits. Although they don't even give it a mentions, presumably they must have had some inkling that it was different to the other little lights as it 'wandered' over the undersurface of the dome, like some of the other little lights - magical mystery, probably involving angels or other magic spirits, no doubt.
But what was it exactly that changed Mars from being a wet planet, with an atmosphere and probably suitable for life to evolve on, to being a cold, dry, unsuitable, even hostile place, where life as we know it could not exist, certainly on its surface or as advanced multicellular organisms.
In the following paper, researchers show how Mars went from potentially suitable for life – with evidence for widespread liquid water on the surface – to a surface that is inhospitable to terrestrial life as we know it* https://www*pnas*org/doi/10*1073/pnas*2321342121* Over what time scale would this have taken place? Mars transitioned from a potentially habitable environment with widespread liquid water to its current inhospitable state over the course of billions of years. Studies suggest that Mars' "wet" period, where liquid water was present, ended roughly 3 billion years ago. Before this, Mars likely had a much thicker atmosphere and conditions that could have supported liquid water on its surface, essential for life as we understand it.This is the subject of a research paper just published in the online journal Proceedings of the National Academy of Science (PNAS). The research team was led by David Burtt of NASA’s Goddard Space Flight Center. Their work is explained in a NASA news release:
As Mars' atmosphere thinned and its climate cooled, the liquid water gradually disappeared, leaving behind only traces of water locked in ice or absorbed into the soil. This dramatic shift made Mars increasingly dry, cold, and inhospitable. Isotope measurements of carbonates from Gale Crater suggest that Mars went through cycles of drying and cooling, leading to environments where only transient or extremely salty liquid water may have existed—both unfavorable for sustaining life as we know it [1.1,2.1,3.1].
How can they tell that from these isotope measurements?
Researchers analyze isotopes, particularly carbon and oxygen isotopes in carbonate minerals, to reconstruct ancient Martian climates and environments. Isotopes are atoms of the same element with different numbers of neutrons, which gives them slightly different physical properties, such as how they interact with other elements or compounds.
For Mars, researchers focus on the ratio of certain carbon isotopes, such as carbon-12 and carbon-13, and oxygen isotopes in minerals like carbonates. These isotopes form in response to environmental conditions, such as temperature, water availability, and atmospheric composition. When water evaporates or precipitates, the heavier isotopes (like carbon-13) can behave differently compared to lighter ones (like carbon-12), creating a signature that is preserved in the minerals.
The carbonate minerals studied in Mars' Gale Crater indicate two possible formation mechanisms: either through wet-dry cycles (where water was present and evaporated), or in very salty, cold conditions. The presence of isotopes associated with extreme evaporation points to a climate that once allowed for liquid water but later experienced cycles of evaporation, leading to a drying and cooling environment over time. This analysis helps scientists infer that liquid water was once present but became transient and increasingly scarce as the planet became inhospitable [1.1,2.1,3.1].
The specific isotope ratios suggest Mars' ancient atmosphere was much thicker and water was stable on the surface, but over time, as the atmosphere thinned, the water evaporated, leaving the cold, dry Mars we see today.
NASA: New Insights into How Mars Became Uninhabitable
NASA’s Curiosity rover, currently exploring Gale crater on Mars, is providing new details about how the ancient Martian climate went from potentially suitable for life – with evidence for widespread liquid water on the surface – to a surface that is inhospitable to terrestrial life as we know it.
Although the surface of Mars is frigid and hostile to life today, NASA’s robotic explorers at Mars are searching for clues as to whether it could have supported life in the distant past. Researchers used instruments on board Curiosity to measure the isotopic composition of carbon-rich minerals (carbonates) found in Gale crater and discovered new insights into how the Red Planet’s ancient climate transformed.
The isotope values of these carbonates point toward extreme amounts of evaporation, suggesting that these carbonates likely formed in a climate that could only support transient liquid water. Our samples are not consistent with an ancient environment with life (biosphere) on the surface of Mars, although this does not rule out the possibility of an underground biosphere or a surface biosphere that began and ended before these carbonates formed.
David Burtt, lead author
NASA’s Goddard Space Flight Center
Greenbelt, Maryland, USA.
Isotopes are versions of an element with different masses. As water evaporated, light versions of carbon and oxygen were more likely to escape into the atmosphere, while the heavy versions were left behind more often, accumulating into higher abundances and, in this case, eventually being incorporated into the carbonate rocks. Scientists are interested in carbonates because of their proven ability to act as climate records. These minerals can retain signatures of the environments in which they formed, including the temperature and acidity of the water, and the composition of the water and the atmosphere.
The paper proposes two formation mechanisms for carbonates found at Gale. In the first scenario, carbonates are formed through a series of wet-dry cycles within Gale crater. In the second, carbonates are formed in very salty water under cold, ice-forming (cryogenic) conditions in Gale crater.
These formation mechanisms represent two different climate regimes that may present different habitability scenarios. Wet-dry cycling would indicate alternation between more-habitable and less-habitable environments, while cryogenic temperatures in the mid-latitudes of Mars would indicate a less-habitable environment where most water is locked up in ice and not available for chemistry or biology, and what is there is extremely salty and unpleasant for life.
Jennifer Stern, co-author
NASA’s Goddard Space Flight Center
Greenbelt, Maryland, USA.
These climate scenarios for ancient Mars have been proposed before, based on the presence of certain minerals, global-scale modeling, and the identification of rock formations. This result is the first to add isotopic evidence from rock samples in support of the scenarios.
The heavy isotope values in the Martian carbonates are significantly higher than what’s seen on Earth for carbonate minerals and are the heaviest carbon and oxygen isotope values recorded for any Mars materials. In fact, according to the team, both the wet-dry and the cold-salty climates are required to form carbonates that are so enriched in heavy carbon and oxygen.
The fact that these carbon and oxygen isotope values are higher than anything else measured on Earth or Mars points towards a process (or processes) being taken to an extreme. While evaporation can cause significant oxygen isotope changes on Earth, the changes measured in this study were two to three times larger. This means two things: 1) there was an extreme degree of evaporation driving these isotope values to be so heavy, and 2) these heavier values were preserved so any processes that would create lighter isotope values must have been significantly smaller in magnitude.
David Burtt.
This discovery was made using the Sample Analysis at Mars (SAM) and Tunable Laser Spectrometer (TLS) instruments aboard the Curiosity rover. SAM heats samples up to nearly 1,652 degrees Fahrenheit (almost 900°C) and then the TLS is used to analyze the gases that are produced during that heating phase.
Funding for this work came from NASA’s Mars Exploration Program through the Mars Science Laboratory project. Curiosity was built by NASA’s Jet Propulsion Laboratory (JPL), which is managed by Caltech in Pasadena, California. JPL leads the mission on behalf of NASA’s Science Mission Directorate in Washington. NASA Goddard built the SAM instrument, which is a miniaturized scientific laboratory that includes three different instruments for analyzing chemistry, including the TLS, plus mechanisms for handling and processing samples.
Publication:Burtt, David G.; Stern, Jennifer C.; Webster, Christopher R., et al.
Highly enriched carbon and oxygen isotopes in carbonate-derived CO2 at Gale crater, Mars Proceedings of the National Academy of Sciences (PNAS)
The only mention of Mars in the Bible is in a reference to Paul standing on Mars Hill (a hill in Greece) and telling the 'Men of Athens' that they are too superstitious![sic] (Acts 17:22) But then both Testaments of the Bible were written by people who believed the Moon hid in 'the valley of Ajalon' at night (Joshua 10:12) and shone with its own internal light, so nothing they have to say on the subject of astronomy and the planets need be taken seriously.Significance
One objective of the Curiosity rover is to search for habitable conditions, past and present, on the surface of Mars. Carbonate minerals can record diagnostic signatures of their formation environment. This paper focuses on carbon and oxygen isotope measurements of carbonate minerals detected within the Gale crater. Notably, these carbonates are extremely enriched in 13C and 18O, more so than other Martian materials. We highlight two processes (evaporation-driven Rayleigh distillation and cryogenic precipitation) that could explain these isotopic enrichments and explore whether those processes are consistent with our current understanding of Mars. These isotopic values offer a poignant example of how the Martian carbon cycle differs from that on Earth without the influences of a biosphere.
Abstract
Carbonate minerals are of particular interest in paleoenvironmental research as they are an integral part of the carbon and water cycles, both of which are relevant to habitability. Given that these cycles are less constrained on Mars than they are on Earth, the identification of carbonates has been a point of emphasis for rover missions. Here, we present carbon (δ13C) and oxygen (δ18O) isotope data from four carbonates encountered by the Curiosity rover within the Gale crater. The carbon isotope values range from 72 ± 2‰ to 110 ± 3‰ Vienna Pee Dee Belemnite while the oxygen isotope values span from 59 ± 4‰ to 91 ± 4‰ Vienna Standard Mean Ocean Water (1 SE uncertainties). Notably, these values are isotopically heavy (13C- and 18O-enriched) relative to nearly every other Martian material. The extreme isotopic difference between the carbonates and other carbon- and oxygen-rich reservoirs on Mars cannot be reconciled by standard equilibrium carbonate–CO2 fractionation, thus requiring an alternative process during or prior to carbonate formation. This paper explores two processes capable of contributing to the isotopic enrichments: 1) evaporative-driven Rayleigh distillation and 2) kinetic isotope effects related to cryogenic precipitation. In isolation, each process cannot reproduce the observed carbonate isotope values; however, a combination of these processes represents the most likely source for the extreme isotopic enrichments.
Carbon is essential for life and for planetary climate regulation, so understanding its potential reservoirs and fluxes is critical to evaluating the habitability of Mars (1–3). Carbonates are one known reservoir for carbon on Mars, having been detected both at the surface (4–11) and in Mars meteorites (12–16). While carbonates exist on Mars, the detected concentrations are unexpectedly low given that carbonates are an expected weathering product of abundant basaltic lithologies in the presence of a CO2-rich atmosphere and liquid water (16). This disparity raises questions about how these carbonates formed and how much of a role these minerals played in sequestering CO2 on Mars. Hypotheses for the origin(s) of these carbonates range from evaporative precipitation (6, 10, 17), supersaturation within lakes or playas (5, 10, 17, 18), groundwater mixing (11), carbonation of peridotite (5, 10, 19), hydrothermal mineralization (5–7, 17, 19), to ultramafic vein-hosted precipitation (5, 17). As these mechanisms demonstrate, carbonates form in direct contact with the carbon and water cycles, which are both necessary for habitability. Furthermore, carbonates can preserve signatures of their source materials and formation conditions, including temperature (20, 21), pH (22), and pCO2 (23). Such data are crucial for understanding the ancient climates and habitability of Mars (24).
Stable isotope geochemistry can clarify the paleoenvironmental information recorded within carbonates. Carbon and oxygen isotope ratios, expressed as δ13C and δ18O, respectively, are dependent on the isotopic composition of source materials and any processes that result in fractionation (i.e., the partitioning of isotopes between two or more phases in a system). In the case of carbonates, the primary source materials are H2O and dissolved CO2, whose isotopic compositions in turn carry fingerprints of their provenance and processes operating on volatile reservoirs on Mars. Therefore, as carbonates are connected to both the carbon and water cycles, the isotopic composition of these carbonates can be used to identify the source materials, fractionating processes, and environmental conditions (e.g., temperature, pH, and salinity) relevant to these cycles on Mars.
Gale crater was selected as the landing site for the Mars Science Laboratory (MSL) Curiosity rover based in part on orbital observations of mineral assemblages that may reflect global-scale changes in climate (25). The lower units within the stratigraphy follow an upward transition from fluvial-lacustrine to aeolian-dominated deposits, indicating that there was a shift from wetter to more arid conditions (25–28). To this point, there have been only scarce orbital (29) and in situ (11, 30–32) measurements to suggest that carbonates are present within the clay- and sulfate-rich units in Gale crater, even though measurements on Earth demonstrate that carbonates can form alongside clay minerals and sulfates on Earth (19, 33). However, the Chemistry & Mineralogy (CheMin) instrument aboard Curiosity recently detected carbonates at multiple drill locations within these stratigraphic units (11, 34). Of these locations, four have corresponding isotopic data: Mary Anning (MA), Bardou (BD), Tapo Caparo (TC), and Ubajara (UB) (32) (Fig. 1). These drill sites span the transition from mixed clay minerals and sulfates (MA and BD), which represent wetter conditions, to sulfates without clay minerals (TC and UB), which reflect a more arid environment. These four drill sites record the highest carbonate abundances detected to this point in Gale crater, suggesting that these carbonates are a significant component of the stratigraphic section and climate. Given this geochemical significance, the Sample Analysis at Mars (SAM) instrument suite analyzed the carbon and oxygen isotopic compositions of the CO2 evolved during pyrolysis of these rock powders. Here, we present these results and discuss potential mechanisms to explain the isotopic enrichments in the carbonates with respect to known carbon and oxygen reservoirs on Mars.
How on Earth can anyone take seriously the nonsense written by people who think the Moon hides in a valley at night?
But none of this will have the slightest influence on the superstitions of creationists who never critically read the Bible nor base their beliefs on evidence. Mars had water on it 3 billion years ago. That is an indisputable fact, yet creationists think a book which says the moon hides in a valley at night and shines with its own internal light while hanging from a dome over the Earth, but neglecting to mention any of the planets, is the best available source book for biology, cosmology and history.
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