Astrobiology Wiki

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

User page Discussion

User:Robertinventor/Simple animals could live in Martian brines - Extended Interview with planetary scientist Vlada Stamenković (edit)

Revision as of 17:22, 13 May 2019

1,603 bytes removed ,  5 years ago
no edit summary
VisualWikitext
No edit summary
Line 51:
[[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.]]
 
===Lowest and highest oxygen concentrations in their maps===▼
===Oxygen requirements for complex life such as sponges===
 
'''''(background information):''''' Saturated sea water is about 9 mg per liter at 20&nbsp;°C ranging up to 11 mg per liter at 0&nbsp;°C because cold water takes up the oxygen more readily.<!-- see for instance the two "Dissolved Oxygen" cites in the Background sources-->.
Line 57:
'''''Note:''''' The paper uses moles per cubic meter. Many other sources use miligrams per liter. To convert moles of oxygen per cubic meter to milligrams per litre multiply by 32.
 
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.▼
Stamenković et al found oxygen levels throughout Mars would be high enough for the least demanding {{w|Aerobic organism|aerobic}} (oxygen-using) microbes, for all the brines they considered, and all the methods of calculation. They published a detailed map<sup>[[#Figure 3|[3]]]</sup> of the distributions of solubility for calcium perchlorates for their more optimistic calculations, which they reckoned were closer to the true case, with and without {{w|Supercooling|supercooling}}. The lowest concentrations were shown in the tropical southern uplands. Brine in regions poleward of about 67.5° to the north and about 72.5° to the south could have oxygen concentrations high enough for simple sponges. 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), for calcium perchlorates. 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 within 0.2 moles per cubic meter, 6.4 mg per liter.<!-- see "Dissolved Oxygen" cites -->
 
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. TheyFor calcium perchlorate brines,they got a level of 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.
 
The paper includes a map of potential brine oxygen concentrations for calcium perchlorates brines on the surface of Mars (their [https://www.nature.com/articles/s41561-018-0243-0/figures/3 figure 3a]). TheseLevels would be higher at the lowest points such as the floor of the {{w|Hellas Planitia|Hellas basin}}, south of the equator, where the atmospheric pressure is highest, reaching around 1% of Earth's atmosphere and lowest of all in the mountainous tropical southern uplands. But the highest values of all would be for brines at the poles.
[[File:PIA22546-Mars-AnnualCO2ice-N&SPoles-20180806.gif|thumb|Extents of north (left) and south (right) polar CO<sub>2</sub> ice during a Martian year. These are not photos, rather they are based on infrared data from two instruments that can study the poles even at times of complete darkness. The dry ice here reaches temperature of around -125&nbsp;°C, well below its sublimation temperature of -78.5&nbsp;°C, which gives an idea of how cold the Martian poles get in winter. In Vlada Stamenković et al's model the highest oxygen concentrations occur at temperatures down to -123 to -133&nbsp;°C.]]▼
 
 
===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. That's where they found there would be enough for simple sponges.
▲[[File:PIA22546-Mars-AnnualCO2ice-N&SPoles-20180806.gif|thumb|Extents of north (left) and south (right) polar CO<sub>2</sub> ice during a Martian year. These are not photos, rather they are based on infrared data from two instruments that can study the poles even at times of complete darkness. The dry ice here reaches temperature of around -125&nbsp;°C, well below its sublimation temperature of -78.5&nbsp;°C, which gives an idea of how cold the Martian poles get in winter. In Vlada Stamenković et al's model the highest oxygen concentrations occur at temperatures down to -123 to -133&nbsp;°C.]]
 
Stamenković et al cite a paper 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"-->.
 
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&nbsp;°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.▼
▲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.
 
For calcium perchlorate brines, regions poleward of about 67.5° to the north and about 72.5° to the south, could have oxygen concentrations high enough for simple sponges. 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).
This new research greatly expands the possibilities for complex life on Mars.▼
 
The brine that achieved the highest oxygen solubility is magnesium perchlorates. With this, oxygen concentrations could reach values as high as two moles per cubic meter (64 mg per liter<!-- atomic weight here http://ciaaw.org/oxygen.htm -->)<!--abstract of paper--> for the best case with supercooling.
▲===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&nbsp;°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.
 
For their calcium perchlorates map with {{w|Supercooling|supercooling}}, the lowest concentrations are around 25 millionths of a mole per cubic meter (0.008 mg per liter). For this brine regions poleward of about 67.5° to the north and about 72.5° to the south, could have oxygen concentrations high enough for simple sponges. 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), for calcium perchlorates. The brine that achieved the highest oxygen solubility is magnesium perchlorates. With this, oxygen concentrations could reach values as high as two moles per cubic meter (64 mg per liter<!-- atomic weight here http://ciaaw.org/oxygen.htm -->)<!--abstract of paper--> for the best case with supercooling.
 
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 within their 0.2 moles (6.4 mg) per liter.<!-- see for instance the two "Dissolved Oxygen" cites in the Background sources-->.
 
▲This new research greatly expands the possibilities for complex life on Mars.
 
==Interview==
Line 126 ⟶ 127:
Wikinews asked Vlada Stamenković 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:
 
:: {{WNIQ}} I notice from your <sup>[https://www.nature.com/articles/s41561-018-0243-0/figures/4 figure[#Figure 4|[4] ]]</sup> 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).
::'''VS''': 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.
[[File:Mars-water-droplets-phoenix-2008-bg.gif|thumb|Unfortunately, the Phoenix lander wasn't equipped to analyze droplets on its legs, which it observed in 2008-9. However, they appear to be droplets of some liquid, most likely salty water, from the way they behaved. These may be our first spacecraft observations of liquid brines on Mars. Nilton Renno's team's research in the University of Michigan's newly built Mars simulation chamber, published in 2014, was able to duplicate them in minutes when salt lies on top of ice. They suggested that such droplets may be common place on Mars today. Wikinews asked Vlada Stamenković if these droplets could be oxygen rich. He said he doesn't know yet, but it is a really good question.]]
Line 250 ⟶ 251:
|date = October 22, 2018
}}
*:{{anchor|Figure 3}}[https://www.nature.com/articles/s41561-018-0243-0/figures/3 Figure 3].
*:{{anchor|Figure 4}}[https://www.nature.com/articles/s41561-018-0243-0/figures/4 Figure 4].
*{{source
|url = https://static-content.springer.com/esm/art%3A10.1038%2Fs41561-018-0243-0/MediaObjects/41561_2018_243_MOESM1_ESM.pdf
Retrieved from "https://encyclopediaofastrobiology.org/wiki/Special:MobileDiff/10220"