User:Robertinventor/Simple animals could live in Martian brines - Extended Interview with planetary scientist Vlada Stamenković: Difference between revisions

The {{w|Atmosphere of Mars|atmosphere of Mars}} is far too thin for us to breathe, or indeed, for lungs like ours to extract oxygen at all. It has around 0.6% of the pressure of Earth's atmosphere, on average. This is mainly carbon dioxide; only 0.146% of that is oxygen. Yet the result of their modeling was clear. In the cold conditions on Mars these minute amounts of oxygen can get into the salty seeps of water which may be present there. What's more, the oxygen levels anywhere on Mars could reach the levels needed to support any microbial life that depends on oxygen.

Some organisms can survive without it, but oxygen permits a more energy-intensive metabolism. Almost all complex multicellular life on Earth depends on oxygen. They found that cold water would take up much more oxygen than warm water. In the coldest salty water in the polar regions, covering perhaps 6.5% of the Martian surface, oxygen levels on Mars may be get high enough for simple animals such as sponges.

[[File:Warm Season Flows on Slope in Newton Crater (animated-cropped).gif|thumb|Seasonal changes in recurrent slope lineae on a steep slope in Newton Crater at 41.6 degrees south latitude on Mars. These long narrow dark streaks form on sun facing slopes when surface temperatures approach the melting point of ice. They extend in spring, broaden through the summer, and fade in autumn. Some water is involved as shown by the presence of hydrated salts, though there is debate about how much is due to water and how much to other processes such as dust flows. This is one of our best current candidates for possibly habitable salty water on [[Mars]].]]

'''''(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&nbsp;°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&nbsp;°C. However, that still means that it is close to boiling point already at 0&nbsp;°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-->

However, salty brines can be liquid at well below 0&nbsp;°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.

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&nbsp;°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. However the hydrated perchlorate salts observation still has to be explained, as well as the seasonal timing, not correlated with the winds. This is considered to be good evidence that there is at least an element of seasonal hydration associated with the streaks. The literature on this topic has a vigorous dialog between researchers who favour greater or lesser elements of brines in this process.

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. [[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]]