Friday, November 9, 2018

Vlada Stamenkovi? and his colleagues have developed a new chemical model of how oxygen dissolves in Martian conditions, which raises the possibility of oxygen-rich brines; enough, the work suggests, to support simple animals such as sponges. The model was published in Nature on October 22. A Wikinews reporter caught up with him in an email interview to find out more about his team’s research and their plans for the future.

The atmosphere of Mars is far too thin for humans to breathe or for lungs like ours to extract any oxygen at all. It has on average only around 0.6% of the pressure of Earth’s atmosphere, and this is mainly carbon dioxide; only 0.145% of that 0.6% is oxygen. The new model indicated that these minute traces of oxygen should be able to enter salty seeps of water on or near the planet’s surface at levels high enough to support life forms comparable to Earth’s microbes, possibly even simple sponges. Some life forms can survive without oxygen, but it permits more energy-intensive metabolism. Almost all complex multicellular life depends on oxygen.

“We were absolutely flabbergasted. I went back to recalculate everything like five different times to make sure it’s a real thing,” Stamenkovi? told National Geographic.

“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,” he went on to tell Scientific American, “implying that if life ever existed on Mars it might have been breathing oxygen.”

Stamenkovi? et al cite research from 2014 that showed that some simple sponges can survive with only 0.002 moles per cubic meter (0.064 mg per liter) . 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.

This isn’t the first time researchers have suggested that multicellular life may exist on Mars. In 2014, de Vera et al using the facilities at the German Aerospace Center (DLR) studied some lichens, including Pleopsidium chlorophanum, which can grow high up in Antarctic mountain ranges. They showed that they can also survive and even grow in Mars simulation chambers. However, they can do this because their algal component is able to produce the oxygen needed by the fungal component. Stamenkovi? et al’s research provides a way for oxygen to get into the brines without algae or photosynthesis.

Stamenkovi? et al found that oxygen levels throughout Mars would be high enough for the least demanding aerobic (oxygen using) microbes, around 25 millionths of a mole per cubic meter (0.0008 mg per liter) even in the southern uplands where concentrations are lowest. They found that at regions poleward of about 67.5° to the north and about ? 72.5° to the south, oxygen concentrations could be high enough for simple sponges, and closer to the poles, concentrations could go higher, approaching levels typical of sea water on Earth, 0.2 moles per cubic meter (6.4 mg per liter). In their paper they described some uncertainties in the calculations but with their best case estimate, which they think is close to the true situation, and supercooling oxygen concentrations could reach higher values as high as two moles per cubic meter (64 mg per liter). On Earth, worms and clams that live in the muddy sea beds require 1 mg per liter, bottom feeders such as crabs and oysters 3 mg per liter, and spawning migratory fish 6 mg per liter, all well within their 0.2 moles per liter.

((Wikinews)) Does your paper’s value of up to 0.2 moles of oxygen per cubic meter, the same as Earth’s sea water mean that there could potentially be life on Mars as active as our sea worms or even fish?
Stamenkovi?: Mars is such a different place than the Earth and we still need to do so much more work before we can even start to speculate.

Stamenkovi? et al studied mixtures of magnesium and calcium perchlorates, common on Mars. They found that the highest oxygen concentrations occur when the water is colder, which happens most in polar regions.

((WN)) The temperatures for the highest levels of oxygen are really low -133 °C, so, is the idea that this oxygen would be retained when the brines warm up to more habitable temperatures during the day or seasonally? Or would the oxygen be lost as it warms up? Or – is the idea that it has to be some exotic biochemistry that works only at ultra low temperatures like Dirk Schulze-Makuch’s life based on hydrogen peroxide and perchlorates internal to the cells as antifreeze?
Stamenkovi?: The options are both: first, cool oxygen-rich environments do not need to be habitats. They could be reservoirs packed with a necessary nutrient that can be accessed from a deeper and warmer region. Second, the major reason for limiting life at low temperature is ice nucleation, which would not occur in the type of brines that we study.

As Stamenkovi? et al explain in the paper, the brines they study smoothly transition to a glassy state after supercooling rather than forming sharp crystals that rip apart the cell as they freeze. They cite simulation experiments that show that these can be supercooled to temperatures as low as -123 to -133 °C before they transition from liquid to a glassy state. They do this even when mixed with the soil of Mars.

The usual cold limit of life cited is -20 °C (not a hard limit because metabolisms slow down at lower temperatures, to the point where individual microbes have lifetimes measured in millennia which his hard to distinguish from dormant life). Stamenkovi? is suggesting that because of the supercooling properties of the brines, life on Mars which usese these brines internally may be able to thrive at temperature more than 110 °C colder than this. Alternatively, he says, it may be able to take advantage of the oxygen in warmer seeps from below that encounter colder layers.

Stamenkovi? et al’s paper is theoretical and is based on a simplified general circulation model of the Mars atmosphere – it ignores distinctions of seasons and the day / night cycle. But it takes account of topography such as mountains and craters etc and the axial tilt. Stamenkovi?’s team combined it with a chemical model of how oxygen would dissolve in the brines and used this to predict oxygen levels in such brines at various locations on Mars.

When asked about plans for a future model that might include seasonal timescales, Stamenkovi? told Wikinews, “Yes, we are now exploring the kinetics part and want to see what happens on shorter timescales.”

Stamenkovi? et al’s model took account of the tilt of the Mars axis, which varies much more than Earth’s does. They found that for the last five million years, conditions were particularly favorable for oxygen-rich brines, and that it continued like this for ten million years into the future, which was as far as they ran the model. For the last twenty million years, as far back as they took their modeling, oases with enough oxygen for sponges were still possible.

Wikinews asked Stamenkovi? if he had any ideas about whether and how sponges could survive through times when the tilt was higher and less oxygen would be available:

((WN)) I notice from your figure 4 that there is enough oxygen for sponges only at tilts of about 45 degrees or less. Do you have any thoughts about how sponges could survive periods of time in the distant past when the Mars axial tilt exceeds 45 degrees, for instance, might there be subsurface oxygen rich oases in caves that recolonize the surface? Also what is the exact figure for the tilt at which oxygen levels sufficient for sponges become possible? (It looks like about 45 degrees from the figure but the paper doesn’t seem to give a figure for this).
Stamenkovi?: 45 deg is approx. the correct degree. We were also tempted to speculate about this temporal driver but realized that we still know so little about the potential for life on Mars/principles of life that anything related to this question would be pure speculation, unfortunately.
((WN)) How quickly would the oxygen get into the brines – did you investigate the timescale?
Stamenkovi?: No, we did not yet study the dynamics. We first needed to show that the potential is there. We are now studying the timescales and processes.

As examples of the dynamics of the Martian atmosphere, the Mars rover Curiosity, which is currently active, measures temperature changes of around 70 °C between day and night. Also there are large pressure differences between summer and winter. In Mars’ Gale crater, pressure varies from under 7.5 mbar to nearly 9.5 mbar. There are also large pressure differences between day and night, varying by 10% compared to a tenth of a percent on Earth. On Earth we see such large pressure differences only during major hurricanes.

((WN)) Could the brines that Nilton Renno and his teams simulated forming on salt / ice interfaces within minutes in Mars simulation conditions get oxygenated in the process of formation? If not, how long would it take for them to get oxygenated to levels sufficient for aerobic microbes? For instance could the Phoenix leg droplets have taken up enough oxygen for aerobic respiration by microbes?
Stamenkovi?: Just like the answer above. Dynamics is still to be explored. (But this is a really good question ?).

Wikinews also asked Stamenkovi? how their research is linked to the recent discovery of possible large subglacial lake 1.5 km below the Martian South Pole found through radar mapping.

((WN)) Some news stories coupled your research with the subglacial lakes announcement earlier this year. Could the oxygen get through ice into layers of brines such as the possible subglacial lakes at a depth of 1.5 km?
Stamenkovi?: There are other ways to create oxygen. Radiolysis of water molecules into hydrogen and oxygen can liberate oxygen in the deep and that O2 could be dissolved in deep groundwater. The radiolytic power for this would come from radionuclides naturally contained in rocks, something we observe in diverse regions on Earth.

Wikinews asked “could it get into a layer of fresh water just 30 cms below clear ice melted by the solid state greenhouse effect, as in Möhlmann’s model (which forms subsurface liquid water at surface temperatures as low as -56 °C).”. In reply, Stamenkovi? suggested the same response, i.e. Radiolysis\Radiolysis from radionuclides in the rocks.

According to Stamenkovi? et al’s paper, present-day Mars would have more oxygen available for life than early Earth had prior to 1.4 billion years ago. They remark in the paper that on Earth, photosynthesis seems to have come first, generating the oxygen for the first animals, while on Mars, which seems to have had different sources of oxygen, oxygen breathers could arise without photosynthesis. The paper concludes by suggesting that this gives broader opportunities for oxygen-breathing life on other planets.

((WN)) And I’d also like to know about your experiment you want to send to Mars to help with the search for these oxygenated brines
Stamenkovi?: We are now developing at “NASA/JPL-California Institute of Technology” a small tool, called TH2OR (Transmissive H2O Reconnaissance) that might one day fly with a yet-to-be-determined mission. It will use low frequency sounding techniques, capable of detecting groundwater at depths down to ideally a few km under the Martian surface, thanks to the high electric conductivity of only slightly salty water and Faraday’s law of induction. Most likely, such a small and affordable instrument could be placed stationary on the planet’s surface or be carried passively or actively on mobile surface assets; TH2OR might be also used in combination with existing orbiting assets to increase its sounding depth. Next to determining the depth of groundwater, we should also be able to estimate its salinity and indirectly its potential chemistry, which is critical information for astrobiology and ISRU (in situ resource utilization).
((WN)) Does your TH2OR use TDEM like the Mars 94 mission – and will it use natural ULF sources such as solar wind, diurnal variations in ionosphere heating and lightning?
Stamenkovi? : The physical principle it uses is the same and this has been used for groundwater detection on the Earth for many decades; it’s Faraday’s law of induction in media that are electrically conducting (as slightly saline water is).
Stamenkovi? : However, we will focus on creating our own signal as we do not know whether the EM fields needed for such measurements exist on Mars. However, we will also account for the possibility of already existing fields.

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