User:Robertinventor/Simple animals could live in Martian brines - Extended Interview with planetary scientist Vlada Stamenković: Difference between revisions
User:Robertinventor/Simple animals could live in Martian brines - Extended Interview with planetary scientist Vlada Stamenković (edit)
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This is an expanded verson of the Wikinews article [https://en.wikinews.org/wiki/Simple_animals_could_live_in_Martian_brines:_Wikinews_interviews_planetary_scientist_Vlada_Stamenkovi%C4%87 Simple animals could live in Martian brines: Wikinews interviews Vlada Stamenković] which I collaborated on, with more background information in it (I'm the volunteer reporter who interviewed him).
==Intro==
<!-- details of atmosphere of Mars in http://science.sciencemag.org/content/341/6143/263 -->
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Some background may help before we get to the main interview with Vlada Stamenković.
(skip to [[#Interview]])
===Why salty water?===
'''''(background information):''''' You might wonder why they
However, salty brines can be liquid at well below 0 °C, for the same reason salt helps keep roads ice free. Salts, and very salty brines counteract the tendency of the water to evaporate at low pressures. They can also take in water from the atmosphere too, in the process known as {{w|Hygroscopy#Deliquescence|deliquescence}}, and
▲'''''(background information):''''' You might wonder why they would focus their research on salty solutions. What about fresh water? It's because it is likely to be rare on present day Mars. Usually the air pressure is so low that fresh water is not stable even at just above freezing, at 0 °C. Mars does have a higher pressure atmosphere at its lowest points such as the depths of the huge ancient impact crater of the {{w|Hellas Planitia|Hellas basin}}, and this does raise the boiling point of fresh water to 10 °C. However, that still means that it is close to boiling point already at 0 °C. If any ice melts, the water would evaporate away rapidly, indeed the pressure is so low that ice also isn't stable at that temperature. <!--see Making a Splash on Mars-->
Curiosity discovered indirect evidence of
▲However, salty brines can be liquid at well below 0 °C, for the same reason salt helps keep roads ice free. Salts, and very salty brines counteract the tendency of the water to evaporate at low pressures. They can also take in water from the atmosphere too, in the process known as deliquescence, and are especially good at doing this at low temperatures.
===The recurring slope lineae===
▲Curiosity discovered indirect evidence of deliquescence in the equatorial regions (through humidity measurements). These regions are so dry that there isn't even any ice in the surface soil, yet it found that brines form during winter nights in the top 15cm of the soil through {{w|Hygroscopy#Deliquescence|deliquescence}}. They take up water from the atmosphere at night when the salts reach temperatures of around -70 °C. This water then evaporates again as the soil warms up through the day, and the process repeats every day - night cycle. <!-- "Evidence of liquid water found on Mars" in background information -->
There is indirect evidence for other salty brines on Mars, perhaps more habitable than the Curiosity brines. In their paper, Stamenković et al. mention the hydrated magnesium and calcium salts associated with the Recurring Slope Lineae. These seasonal streaks form in spring on sun facing slopes, extend and broaden through the summer and fade away in autumn. The streaks themselves are not damp patches, but they may be associated with thin seeps of brine just below the surface. Later research suggests dust flows may also be involved.
[[Image:Martian conditions in miniature (7494313830) (2).jpg|thumb|Experiments by DLR (German aerospace company) in Mars simulation chambers and on the ISS show that some lichens such as {{w|Pleopsidium chlorophanum}} can survive Mars surface conditions and photosynthesize and metabolize, slowly, using only the humidity of the Mars atmosphere. The algal component provides oxygen for the fungal component, giving a way for multicellular life to survive without any oxgyen on Mars]]
===Significance of oxygen===
Before these new results, scientists assumed any present day Martian life would be able to grow without oxygen. There are several possibilities for this, based on Mars simulation experiments. Martian life could include certain blue-green algae such as {{w|Chroococcidiopsis#Mars colonization|chroococcidiopsis}}, some black fungi, and some purple salt loving {{w|Haloarchaea#As exophiles|haloarchaea}} found in salt ponds and hypersaline lakes on Earth. <!--for the black fungi, Zakharova et al paper in background information-->. Some lichens such as {{w|Pleopsidium chlorophanum}} also have some potential for surviving in Mars surface conditions without oxygen. They can do this because the algal component is able to make the oxygen needed by its fungal component.
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::'''VS''': Our work is calling for a complete revision for how we think about the potential for life on Mars, and the work oxygen can do, implying that if life ever existed on Mars it might have been breathing oxygen<!--Scientific American-->
[[File:Halichondria panicea.jpg|thumb|Halichondria panicea or the breadcrumb sponge- Stamenković et al's paper cites research by Mills et al using this sponge which showed it can survive with only 0.002 moles per cubic meter (0.064 mg per liter). This new research suggests that these concentrations can be achieved in {{w|Supercooling|supercooled}} brines on modern Mars in polar regions.]]
===Oxygen requirements for complex life such as sponges===
'''''(background information):''''' Stamenković et al in their paper cite research from 2014 that showed that some simple sponges can survive with only 0.002 {{w|Mole (unit)|moles}}per cubic meter (0.064 mg per liter) <!-- first page of Nature paper, "Meanwhile, whereas aerobic microbial life and simple animals need O<sub>2</sub> dissolved in liquids in sufficiently large concentrations to survive, recent experiments, observations and calculations have lowered the required limits of concentrations of dissolved O<sub>2</sub> for aerobic respiration to ~10−6 mol m−3 in microorganisms and to ~2 × 10−3 mol m−3 in sponges"-->. Some microbes that need oxygen can survive with as little as a millionth of a mole per cubic meter (0.000032 mg, or 32 nanograms per liter). In their model, they found that there can be enough oxygen for microbes throughout Mars, and enough for simple sponges in oases near the poles.
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Stamenković et al found that even in the worst case they could devise, oxygen levels throughout Mars would be enough for the least demanding {{w|Aerobic organism|aerobic}} (oxygen using) microbes, at around 2.5 millionths of a mole per cubic meter (0.0008 mg per liter). That's the value for the tropical southern uplands, where temperatures are high and the atmosphere is thin, and for their brine with the lowest oxygen solubilities, sodium perchlorate. They also calculated this figure using their worst case estimate (where they do the calculations on their least optimistic assumptions). However, they give reasons for believing that their more optimistic best case calculations are close to the true situation.
===Lowest and highest oxygen concentrations in their maps===
The highest oxygen concentrations of all, occur when the water is colder, which is most easily attained in polar regions. They paid particular attention to two brines, magnesium and calcium perchlorates, common on Mars. In simulation experiments these stay liquid as they are {{w|Supercooling|supercooled}} to temperatures as low as -123 to -133 °C before they transition to a glassy state. They do this even when mixed with the soil of Mars (regolith). It's at these very low temperatures that the optimal oxygen concentrations can be reached.
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