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Thread: Is Mars Too Dry for Life?

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    Is Mars Too Dry for Life?

    An interesting study paper and article recently showed up:

    Paper: Constraints on the Metabolic Activity of Microorganisms in Atacama Surface Soils Inferred from Refractory Biomarkers: Implications for Martian Habitability and Biomarker Detection

    Article: Is Mars' soil too dry to sustain life?

    The article comes to some very interesting conclusions (my underlines):
    ... All life on Earth is built with "left-handed" amino acid molecules. However, when a cell dies, some of its amino acids change at a known rate into the reflecting "right-handed" structure, eventually balancing into a 50-50 ratio over many years. By looking at this ratio in the driest Atacama soils, the scientists found microbes there that have been dead for at least 10,000 years. Finding even the remnants of life this old is extremely rare, and surprising for a sample sitting in the surface of Earth.

    Getting Ready for Mars:

    Mars is 1,000 times drier than even the driest parts of the Atacama, which makes it less likely that microbial life as we know it exists on the planet's surface, even with some access to water. However, even in the driest areas of Chile's desert, remnants of past microbial life from wetter times in the Atacama's history were clearly present and well preserved over thousands of years. This means that because scientists know that Mars was a wetter, more vibrant planet in its past, traces of that ancient life might still be intact.
    Perhaps those blueberries might really turn out to be 10,000 year old dessicated/fossilised martian fruit after all, eh?

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    The trouble with this theory is Mars has been this dry for many millions (billions?) of years, not just 10,000 years.

    Also Mars surface is not well shielded from cosmic rays because it has little magnetic field and atmosphere.

    High energy particles tend to destroy organic molecules over long time periods. About a metre under the surface the cosmic ray dose is a lot lower and that might be the place to look.

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    http://science.sciencemag.org/conten...e.aar7268.full

    Just out now. So much for a dry Mars. Underground lake!
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    Quote Originally Posted by Roger E. Moore View Post
    http://science.sciencemag.org/conten...e.aar7268.full

    Just out now. So much for a dry Mars. Underground lake!
    Nice!! Ice fishing anyone?
    We know time flies, we just can't see its wings.

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    Hmmm .. interesting find but I don't think this discovery necessarily contradicts much of what is said in the OP study. In fact, if anything, it re-inforces the notion of the Atacama desert being an even closer analogy than it was prior to the subsurface detection of the proposed polar sub-surface liquid lake!

    Also, they're not exactly talking about a subsurface lake of pure water:
    From the recent discovery paper:
    Quote Originally Posted by Orosei
    The substantial amounts of magnesium, calcium, and sodium perchlorate in the soil of the northern plains of Mars, discovered using the Phoenix landers Wet Chemistry Lab (29), support the presence of liquid water at the base of the polar deposits. Perchlorates can form through different physical and/or chemical mechanisms (30, 31) and have been detected in different areas of Mars. It is therefore reasonable to assume that they are also present at the base of the SPLD. Because the temperature at the base of the polar deposits is estimated to be around 205 K (32), and because perchlorates strongly suppress the freezing point of water (to a minimum of 204 and 198 K for magnesium and calcium perchlorates, respectively) (29), we therefore find it plausible that a layer of perchlorate brine could be present at the base of the polar deposits. The brine could be mixed with basal soils to form a sludge or could lie on top of the basal material to form localized brine pools (32).
    So, in terms of a life-relevant discovery .. well I'm not so sure. The question becomes (more or less): does life like subsurface (approx 1.5kms?) liquid perchlorate brines?

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    Quote Originally Posted by Selfsim View Post
    Hmmm .. interesting find but I don't think this discovery necessarily contradicts much of what is said in the OP study. In fact, if anything, it re-inforces the notion of the Atacama desert being an even closer analogy than it was prior to the subsurface detection of the proposed polar sub-surface liquid lake!

    Also, they're not exactly talking about a subsurface lake of pure water:
    From the recent discovery paper:
    So, in terms of a life-relevant discovery .. well I'm not so sure. The question becomes (more or less): does life like subsurface (approx 1.5kms?) liquid perchlorate brines?
    Just to point out, perchlorate is a kinetically inert oxidant, and as such has potential for powering life. All you need is a geological source of methane or sulphides to react with it, with enzymes to speed up the process.

    But I have to admit it is a difficult scenario if the perchlorate is as concentrated as hypothesised.

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    Quote Originally Posted by kzb View Post
    Just to point out, perchlorate is a kinetically inert oxidant, and as such has potential for powering life. All you need is a geological source of methane or sulphides to react with it, with enzymes to speed up the process.
    I suppose the soil ph leaning towards alkaline also supports what you say here(?)

    Perchlorateogenic martian life, eh?
    Perhaps we can put this alongside Chris McKay's methanogenic Titan life? This list is probably endless .. but note how we continue to hypothesize lifeform chemstries specific to the planet/moon/object under question, and yet we continue to also continue to expect that it will end up exhibiting the same detectable processes as Earth-life, (metabolism, reproduction, homeostasis, etc)? Somehow the chemistry argument takes a quantum leap of faith away from its own fundamental physical principles to somehow produce life (as we know it). I wonder why that is?

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    Quote Originally Posted by Selfsim View Post
    Perchlorateogenic martian life, eh?
    If we're going to use technical suffixes like "-genic", it's worth checking what they mean. The suffix "-genic" means "producing". It does not mean "consuming as an energy source"...

    Perhaps we can put this alongside Chris McKay's methanogenic Titan life? This list is probably endless .. but note how we continue to hypothesize lifeform chemstries specific to the planet/moon/object under question, and yet we continue to also continue to expect that it will end up exhibiting the same detectable processes as Earth-life, (metabolism, reproduction, homeostasis, etc)? Somehow the chemistry argument takes a quantum leap of faith away from its own fundamental physical principles to somehow produce life (as we know it). I wonder why that is?
    From fundamental principles of physics (the laws of thermodynamics), scientists have worked out that metabolism, reproduction, and homeostasis cannot happen without a source of energy. So, if we are interested in whether or not a particular site (e.g. on Mars) may have life, one of the first questions to look at is whether or not energy sources are present... If a lake contains both oxygen-rich perchlorate and hydrogen-rich compounds like methane or hydrogen sulfide, then the answer to that question is yes...

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    Quote Originally Posted by Colin Robinson View Post
    If we're going to use technical suffixes like "-genic", it's worth checking what they mean. The suffix "-genic" means "producing". It does not mean "consuming as an energy source"
    ...
    From fundamental principles of physics (the laws of thermodynamics), scientists have worked out that metabolism, reproduction, and homeostasis cannot happen without a source of energy. So, if we are interested in whether or not a particular site (e.g. on Mars) may have life, one of the first questions to look at is whether or not energy sources are present... If a lake contains both oxygen-rich perchlorate and hydrogen-rich compounds like methane or hydrogen sulfide, then the answer to that question is yes...
    Ok .. fair enough then .. (the nomenclature point taken).

    So what would be the products of this reaction (so we can name the lifeform) .. and also maybe even the energy levels by comparison with our own metabolism?
    (The latter being needed in order to say 'yes' that reaction is actually feasible in this environment under those conditions).
    Last edited by Selfsim; 2018-Jul-28 at 03:47 AM.

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    Quote Originally Posted by Selfsim View Post
    Ok .. fair enough then .. (the nomenclature point taken).

    So what would be the products of this reaction (so we can name the lifeform) .. and also maybe even the energy levels by comparison with our own metabolism?
    (The latter being needed in order to say 'yes' that reaction is actually feasible in this environment under those conditions).
    Thanks for these questions.

    I've found a paper about perchlorate-consuming microbes which have already been discovered here on Earth. The paper provides information about their inputs, outputs and the energy levels of their metabolic reactions, as well as explaining why these microbes are considered beneficial.

    According to the paper, they mostly input acetate as well as perchlorate, but some input other substances instead of acetate, including hydrocarbons. Oxygen (O2) is an intermediate product — it doesn't accumulate because the organisms react it with hydrogen from the acetate (or hydrocarbon) to produce H2O. Another characteristic end product is the chloride ion (Cl-).

    The energy yields which these organisms get from their perchlorate are somewhat less than they'd get by starting with molecular oxygen. But it's still a viable way to make a thermodynamic living if you're a microbe in an environment where there is no O2 to use.

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    Quote Originally Posted by Colin Robinson View Post
    Thanks for these questions.

    I've found a paper about perchlorate-consuming microbes which have already been discovered here on Earth. The paper provides information about their inputs, outputs and the energy levels of their metabolic reactions, as well as explaining why these microbes are considered beneficial.

    According to the paper, they mostly input acetate as well as perchlorate, but some input other substances instead of acetate, including hydrocarbons. Oxygen (O2) is an intermediate product — it doesn't accumulate because the organisms react it with hydrogen from the acetate (or hydrocarbon) to produce H2O. Another characteristic end product is the chloride ion (Cl-).

    The energy yields which these organisms get from their perchlorate are somewhat less than they'd get by starting with molecular oxygen. But it's still a viable way to make a thermodynamic living if you're a microbe in an environment where there is no O2 to use.
    Hmm .. interesting .. this paper seems to also confirm what kzb said in post #6.

    Acetate, I would imagine, would not be particularly easy to come by in the martian environment we're talking about, but sulphides (H2S) would make it quite interesting.
    I doubt there would be any active volcanic sources underneath the polar ice cap, (but we do have these here on Earth, IIRC). I seem to recall that sulphides were detected in some SAM GC-MS results of some rock sample testing by Curiosity(?) .. but that's a long way from this region.

    Perchlorate consuming protobacteria underneath the south polar ice caps of Mars, eh? 'Twould be a pretty safe bet to say it would not be an easy existence for them though .. and where are the signs of their predators further up the food chain?

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    Quote Originally Posted by Selfsim View Post
    Hmm .. interesting .. this paper seems to also confirm what kzb said in post #6.

    Acetate, I would imagine, would not be particularly easy to come by in the martian environment we're talking about, but sulphides (H2S) would make it quite interesting.
    I doubt there would be any active volcanic sources underneath the polar ice cap (1), (but we do have these here on Earth, IIRC). I seem to recall that sulphides were detected in some SAM GC-MS results of some rock sample testing by Curiosity(?) .. but that's a long way from this region.

    Perchlorate consuming protobacteria underneath the south polar ice caps of Mars, eh? 'Twould be a pretty safe bet to say it would not be an easy existence for them though (2).. and where are the signs of their predators further up the food chain? (3)


    (1) What I am wondering is, if Mars is geologically dead, what is keeping this water in the liquid state underneath a frozen ice cap? It can only be geological activity. If we have that we also could have volcanic gases being released.

    (2) No it won't be an easy existence, and this is the biggest problem. The concentration of perchlorate salts would need to be very high to give the freezing point depression to 204 K. It might be too strong an oxidant to allow organic matter to persist. But then again I do not know what actual evidence there is for this temperature. It seems to me if there is indeed geological activity keeping it liquid, then we could hypothesise much higher temperatures, and therefore much lower salt concentrations.

    (3) Well no-one's looked yet. It's quite feasible there would be a food chain, but all its members would all be confined to this lake, which is hidden from view.

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    Quote Originally Posted by Colin Robinson View Post
    Thanks for these questions.

    I've found a paper about perchlorate-consuming microbes which have already been discovered here on Earth. The paper provides information about their inputs, outputs and the energy levels of their metabolic reactions, as well as explaining why these microbes are considered beneficial.

    According to the paper, they mostly input acetate as well as perchlorate, but some input other substances instead of acetate, including hydrocarbons. Oxygen (O2) is an intermediate product — it doesn't accumulate because the organisms react it with hydrogen from the acetate (or hydrocarbon) to produce H2O. Another characteristic end product is the chloride ion (Cl-).

    The energy yields which these organisms get from their perchlorate are somewhat less than they'd get by starting with molecular oxygen. But it's still a viable way to make a thermodynamic living if you're a microbe in an environment where there is no O2 to use.
    Agreed, thanks for the link, also like to point out there isn't much difference in energy potential between perchlorate and O2. +1.20V versus +1.229V so there is not much in it.

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    Another thing: with all this perchlorate around, I trust that any prospective Mars geologists are aware that striking a rock with a hammer might cause it to blow up in their face ?

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    Quote Originally Posted by kzb View Post
    (1) What I am wondering is, if Mars is geologically dead, what is keeping this water in the liquid state underneath a frozen ice cap? It can only be geological activity. If we have that we also could have volcanic gases being released.

    (2) No it won't be an easy existence, and this is the biggest problem. The concentration of perchlorate salts would need to be very high to give the freezing point depression to 204 K. It might be too strong an oxidant to allow organic matter to persist. But then again I do not know what actual evidence there is for this temperature. It seems to me if there is indeed geological activity keeping it liquid, then we could hypothesise much higher temperatures, and therefore much lower salt concentrations.

    (3) Well no-one's looked yet. It's quite feasible there would be a food chain, but all its members would all be confined to this lake, which is hidden from view.

    As to your first point, perchlorates can significantly lower freezing point of brines, down to -67oC (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5715023/), so an energy source may not be needed. However, one would be needed to maintain an ecosystem.
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    Quote Originally Posted by kzb View Post
    Agreed, thanks for the link, also like to point out there isn't much difference in energy potential between perchlorate and O2. +1.20V versus +1.229V so there is not much in it.
    According to the linked review paper, "thermodynamics of perchlorate reduction (ΔG = −801 kJ mol acetate−1) are close to nitrate reduction (ΔG = −792 kJ mol acetate−1) and significantly lower than e− transport to O2 (ΔG = −844 kJ mol acetate−1)."

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    Quote Originally Posted by Colin Robinson View Post
    According to the linked review paper, "thermodynamics of perchlorate reduction (ΔG = −801 kJ mol acetate−1) are close to nitrate reduction (ΔG = −792 kJ mol acetate−1) and significantly lower than e− transport to O2 (ΔG = −844 kJ mol acetate−1)."
    801 kJ/mole for perchlorate versus 844 kJ/mole for O2 then ? That's about 5% less available energy, I wouldn't say that is a show stopper ?

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    Quote Originally Posted by swampyankee View Post
    As to your first point, perchlorates can significantly lower freezing point of brines, down to -67oC (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5715023/), so an energy source may not be needed. However, one would be needed to maintain an ecosystem.
    The energy source for maintaining the ecosystem would be perchlorate oxidation of hydrogen sulphide, methane or hydrogenous species in general. So no source of heat needed for that, per se.

    But I don't understand why a source of heat is not needed to keep the solution from freezing, even if it is saturated in perchlorate salts. It's under a thick layer of ice at the poles of Mars, which are very cold. The southern polar cap is so cold it has a permanent layer of frozen CO2.

    And another thing: if this mechanism can keep water liquid, it doesn't apply only in this one location. There could be underground layers of liquid perchlorate solution anywhere on the planet.

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    Quote Originally Posted by kzb View Post
    The energy source for maintaining the ecosystem would be perchlorate oxidation of hydrogen sulphide, methane or hydrogenous species in general. So no source of heat needed for that, per se.

    But I don't understand why a source of heat is not needed to keep the solution from freezing, even if it is saturated in perchlorate salts. It's under a thick layer of ice at the poles of Mars, which are very cold. The southern polar cap is so cold it has a permanent layer of frozen CO2.

    And another thing: if this mechanism can keep water liquid, it doesn't apply only in this one location. There could be underground layers of liquid perchlorate solution anywhere on the planet.
    Perchlorate reduction works until the perchlorates run out, so an external source of energy is needed to replenish it.
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    I think we might be getting a little carried away with the idea that perchlorates are present subsurface .. Firstly, the perchlorate is only pure speculation on the part of ESA, and is probably aimed at 'toning down' their initial speculations about subsurface lake-dwelling martian life. (The latter argument being needed in order to justify, somehow, sending an upcoming martian lab/rover capable of drilling/analysing to 2m depths ).

    Secondly, I think one needs to remember that this water is thought to have originated at the equatorial regions, when Mars' tilt was more extreme.

    Thirdly, the perchlorate is the end product of prolonged solar/UV exposure, and is thus more likely to be confined to the surface soils.

    That being said, the Phoenix lander (at the northern polar region) did detect perchlorates in surface soil samples ..

    Put all that together, and I think the polar surface needs to be considered separately from the sub-surface.
    From surface chemistry (Phoenix):

    Quote Originally Posted by Wiki
    Analysis of the Phoenix WCL also showed that the Ca(ClO4)2 in the soil has not interacted with liquid water of any form, perhaps for as long as 600 million years. If it had, the highly soluble Ca(ClO4)2 in contact with liquid water would have formed only CaSO4. This suggests a severely arid environment, with minimal or no liquid water interaction.

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    Ca(ClO4)2 + H20 = CaSO4 ? What's the source of the sulfur?

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    Quote Originally Posted by Spacedude View Post
    Ca(ClO4)2 + H20 = CaSO4 ? What's the source of the sulfur?
    Extant to the soil:
    Quote Originally Posted by Wiki
    The elements detected and measured in the samples are chloride, bicarbonate, magnesium, sodium, potassium, calcium, and sulfate. Further data analysis indicated that the soil contains soluble sulfate (SO3) at a minimum of 1.1% and provided a refined formulation of the soil.

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    Recent papers.... in case anyone wants to catch up with the conversation.

    =================================

    https://arxiv.org/abs/1708.00518

    Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data

    Wilson, Jack T.; Eke, Vincent R.; Massey, Richard J.; Elphic, Richard C.; Feldman, William C.; Maurice, Sylvestre; Teodoro, Lus F. A.
    01/2018

    We present a map of the near subsurface hydrogen distribution on Mars, based on epithermal neutron data from the Mars Odyssey Neutron Spectrometer. The map's spatial resolution is approximately improved two-fold via a new form of the pixon image reconstruction technique. We discover hydrogen-rich mineralogy far from the poles, including ~10 wt.% water equivalent hydrogen (WEH) on the flanks of the Tharsis Montes and >40 wt.% WEH at the Medusae Fossae Formation (MFF). The high WEH abundance at the MFF implies the presence of bulk water ice. This supports the hypothesis of recent periods of high orbital obliquity during which water ice was stable on the surface. We find the young undivided channel system material in southern Elysium Planitia to be distinct from its surroundings and exceptionally dry; there is no evidence of hydration at the location in Elysium Planitia suggested to contain a buried water ice sea. Finally, we find that the sites of recurring slope lineae (RSL) do not correlate with subsurface hydration. This implies that RSL are not fed by large, near-subsurface aquifers, but are instead the result of either small ( < 120 km diameter) aquifers, deliquescence of perchlorate and chlorate salts or dry, granular flows.

    ================================

    http://adsabs.harvard.edu/abs/2018E%26PSL.497..161T

    Chlorate brines on Mars: Implications for the occurrence of liquid water and deliquescence

    Toner, J. D.; Catling, D. C.
    09/2018

    Oxychlorine salts (chlorates and perchlorates) are globally important components of surface soils on Mars, and could form liquid water in concentrated salt solutions despite prevailing cold and dry conditions. Although perchlorate salts are well-characterized, basic thermodynamic properties of chlorate solutions, such as water activity (aw) and even solubility, are poorly known. To address this knowledge-gap, we measured water activities and solubilities in the Na-Ca-Mg-ClO3 system at 25 C using the isopiestic method, and fit the data to an aqueous ion-interaction Pitzer model. We find that chlorate solutions have extremely low water activities that could allow liquid water to form on the surface of Mars. Compared to perchlorates, chlorates generally have higher water activities at the same concentration; however, saturated Mg(ClO3)2 solutions, in particular, are extremely concentrated (7.59 mol kg-1) and have aw = 0.2 at 25 C, substantially below saturated Mg(ClO4)2 solutions (aw = 0.4). If Mg(ClO3)2 salts are present on Mars' surface, then our results suggest a much greater potential for liquid water formation in soils due to freezing point depression or deliquescence than with perchlorates.

    ======================================

    http://adsabs.harvard.edu/abs/2018P%26SS..157...10H

    Young, small-scale surface features in Meridiani Planum, Mars: A possible signature of recent transient liquid and gas emissions

    Horne, David J.
    08/2018

    Enigmatic small-scale (<1 m) depositional and erosional features found in basaltic sands partly covering bedrock exposures, imaged at several locations in the equatorial Meridiani Planum region by the Mars Exploration Rover Opportunity, may be evidence of previously unrecognized, geologically young (or even contemporary) Martian surface processes. Leveed fissures appear to have formed by venting from beneath; possible explanations include aeolian blowholes near crater margins, volcanic fumarole activity, or gas/vapour escape resulting from the decomposition of small pockets of ground ice, methane clathrates or hydrated sulphate minerals. Some leveed fissures cross-cut and are therefore younger than aeolian ripples thought to have last been active c. 50,000 years ago. Erosional gutters are sharply defined and fresh-looking, internally terraced, sometimes are deeper near one end, and in one case seem to give way to small depositional fans downslope; they have the appearance of having been formed by liquid flow rather than by wind erosion. There is evidence elsewhere that contemporary ground-ice thaw and consequent transient surface run-off may occur occasionally under present conditions at low, near-equatorial latitudes on Mars; short-lived (even for just a few minutes) meltwater emission and flow at the surface could form gutters before evaporating. Further possibilities are the decomposition of buried pockets of methane clathrates (which theoretical considerations suggest might be present and stable even in equatorial regions) giving rise to both methane gas venting and transient surface water, or the release of liquid brines by decomposition of hydrated magnesium sulphate minerals or deliquescence of perchlorates. Dry granular flow mechanisms proposed as explanations for Recurring Slope Lineae seem inadequate to explain the morphologies of leveed fissures and gutters.

    ================================================== =

    http://adsabs.harvard.edu/abs/2017AGUFM.P51H..08F

    The Effect of Gamma Radiation on Mars Mineral Matrices: Implications for Perchlorate Formation on Mars

    Fox, A. C.; Eigenbrode, J. L.; Pavlov, A.; Lewis, J.
    12/2017

    Observations by the Phoenix Wet Chemistry Lab of the Martian surface indicate the presence of perchlorate in high concentrations. Additional observations by the Sample Analysis at Mars and the Viking Landers indirectly support the presence of perchlorate at other localities on Mars. The evidence for perchlorate at several localities on Mars coupled with its detection in Martian meteorite EETA79001 suggests that perchlorate is present globally on Mars. The presence of perchlorate on Mars further complicates the search for organic molecules indicative of past life. While perchlorate is kinetically limited in Martian conditions, the intermediate species associated with its formation or decomposition, such as chlorate or chlorite, could oxidize Martian organic species. As a result, it is vital to understand the mechanism of perchlorate formation on Mars in order to determine its role in the degradation of organics. Here, we explore an alternate mechanism of formation of perchlorate by bombarding Cl-salts and Mars-relevant mineral mixtures with gamma radiation both with and without the presence of liquid water, under vacuum. Previous work has shown that OClO can form from both UV radiation and energetic electrons bombardment of Cl-ices or Cl-salts, which then reacts with either OH- or O-radicals to produce perchlorate. Past research has suggested that liquid water or ice is the source of these hydroxyl and oxygen radicals, which limits the location of perchlorate formation on Mars. We demonstrate that trace amounts of perchlorate are potentially formed in samples containing silica dioxide or iron oxide and Cl-salts both with and without liquid water. Perchlorate was also detected in a portion of samples that were not irradiated, suggesting possible contamination. We did not detect perchlorate in samples that contained sulfate minerals. If perchlorate was formed without liquid water, it is possible that oxide minerals could be a potential source of oxygen radicals required to produce perchlorate. This finding could help explain the global presence of perchlorate and has implications for the survival of organic molecules on Mars.
    Last edited by Roger E. Moore; 2018-Aug-01 at 08:19 PM.
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    Quote Originally Posted by Roger E. Moore View Post
    Recent papers.... in case anyone wants to catch up with the conversation.
    Hmm .. interesting .. Thanks for those links there, Roger E. Moore.

    This one caught my eye in particular: 'The Effect of Gamma Radiation on Mars Mineral Matrices: Implications for Perchlorate Formation on Mars'

    Quote Originally Posted by Fox, etal
    ... Past research has suggested that liquid water or ice is the source of these hydroxyl and oxygen radicals, which limits the location of perchlorate formation on Mars. We demonstrate that trace amounts of perchlorate are potentially formed in samples containing silica dioxide or iron oxide and Cl-salts both with and without liquid water. Perchlorate was also detected in a portion of samples that were not irradiated, suggesting possible contamination. We did not detect perchlorate in samples that contained sulfate minerals. If perchlorate was formed without liquid water, it is possible that oxide minerals could be a potential source of oxygen radicals required to produce perchlorate. This finding could help explain the global presence of perchlorate and has implications for the survival of organic molecules on Mars.
    (My underlines).

    Maybe ... but there is also still no evidence of subsurface (polar) perchlorate .. ie: it might still be constrained to the surface.

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    'Young, small-scale surface features in Meridiani Planum, Mars: A possible signature of recent transient liquid and gas emissions. Horne, David J, 08/2018'
    .. man .. that one was quick off the press .. Aug 2018!!

    Anyway, its about the equatorial regions .. which has different processes from polar.

    PS: Same goes for: '
    Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data. Wilson etal, 01/2018'
    Last edited by Selfsim; 2018-Aug-01 at 10:58 PM. Reason: PS

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    I think the melting/freezing cycles of the polar regions (seasonal and orbital obliquity) may, perhaps, be more relevant to the polar liquid water lake finding(?)
    The water may have circulated away from the equatorial regions and condensed at the poles but the evidently liquid state of the lake, may be because of the insulating effect of the covering ice caps, combined with summer heat transmission through the thinner summer covering(?)

    I don't think any onsight ground temperature measurements have ever really been performed anywhere on the martian soils which seems like a pretty major oversight (IMO) .. (This may well be due to, (perhaps), the obsession with finding organics/life molecules?)

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    Relevant paper? See if it is.

    ==========================

    http://cdsads.u-strasbg.fr/abs/2018AcAau.146..144J

    Shallow transient liquid water environments on present-day mars, and their implications for life

    Jones, Eriita G.
    05/2018

    The identification and characterisation of subsurface liquid water environments on Mars are of high scientific interest. Such environments have the potential to support microbial life, and, more broadly, to develop our understanding of the habitability of planets and moons beyond Earth. Given our current state of knowledge of life on Earth, three pre-requisites are necessary for an environment to be considered 'habitable' and therefore capable of supporting terrestrial-like life: energy, biogenic elements, and liquid water with a sufficiently high water activity. The surface of Mars today is predominately cold and dry, and any liquid water exposed to the atmosphere will vaporise or freeze on timescales of hours to days. These conditions have likely persisted for much of the last 10 million years, and perhaps longer. Despite this, briny liquid water flows (Recurrent Slope Linea) have been observed in a number of locations in the present-day. This review examines evidence from the Phoenix Lander (2008) and the Mars Science Laboratory (2012-current), to assess the occurrence of habitable conditions in the shallow Martian regolith. It will be argued that shallow, transient, liquid water brines are potentially habitable by microbial life, are likely a widespread occurrence on Mars, and that future exploration aimed at finding present-day habitable conditions and potential biology should 'follow the salt'.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    Mark Twain, Life on the Mississippi (1883)

  28. #28
    Join Date
    Apr 2005
    Posts
    2,463
    [QUOTE=Roger E. Moore;2457477]Relevant paper? See if it is.

    ==========================

    http://cdsads.u-strasbg.fr/abs/2018AcAau.146..144J

    Shallow transient liquid water environments on present-day mars, and their implications for life

    Jones, Eriita G.
    05/2018


    Is there a non-paywall version somewhere?

  29. #29
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    3,152
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    Mark Twain, Life on the Mississippi (1883)

  30. #30
    Join Date
    Aug 2018
    Posts
    1
    There seems to have found water.

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