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 05:23, 24 October 2019

1,158 bytes added ,  4 years ago
no edit summary
VisualWikitext
No edit summary
Line 6:
------------------
{{date|November 9, 2018}}
Planetary scientist Vlada Stamenković of the [[NASA]] [[Jet Propulsion Laboratory]] and colleagues have developed a new chemical model of how oxygen dissolves in [[Mars|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 ''{{w|Nature (journal)|Nature}}'' on October 22 2018. ''Wikinews'' caught up with him in an email interview to find out more about his team's research and their plans for the future.
 
''Wikinews'' caught up with him in an email interview to find out more about his team's research and their plans for the future.
[[File:Vlada Stamenković.jpg|thumb|right|Dr. Vlada Stamenković [[Jet Propulsion Laboratory|JPL]] ]]
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 and his answers to some additional questions I asked via email (I'm the volunteer reporter who interviewed him).
 
==Intro==
Line 14 ⟶ 16:
<!-- details of atmosphere of Mars in http://science.sciencemag.org/content/341/6143/263 -->
[[File:Vlada Stamenković.jpg|thumb|left|Dr. Vlada Stamenković - planetary scientist at JPL and lead author of the paper. Wikinews interviewed him about the new Mars research via email.]]
The {{w|Atmosphere of Mars|atmosphere of Mars}} is far too thin for us to breathe,. orIt would not be indeed,possible for lungs like ours to extract oxygen at all. It has around 0.6% ofbecause the pressuremoisture oflining Earth'sour atmosphere,lungs onwould average.boil Thisat iswell mainlybelow carbonblood dioxide;temperature only 0.146% of that is oxygen. Yetin the resultthin ofatmosphere their(much modeling was clear. Inlike the coldway conditionsthat on Mars these minute amounts of oxygenyou can't getmake intoa thegood salty seepscup of watertea whichat mayEverest bebase presentcamp there. What's more,because the oxygenwater levelsboils anywhereat ontoo Marslow coulda reach the levels needed to support any microbial life that depends on oxygentemperature).
 
The Mars atmosphere has a pressure of only 0.6% of Earth's atmosphere, on average. Also it's mainly carbon dioxide; only 0.146% of that 0.6% 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 microbial life. Any microbes that depend on oxygen should manage fine in the Martian brines. There's a caveat here, they don't know how long it would take to reach those levels but once it reaches equilibrium with the atmosphere then that's how much oxygen there should be in the brines.
 
Some organisms can survive without it, but oxygenOxygen permits a more energy- intensive metabolism., and many microbes and Almostalmost all complex multicellular life on Earth dependsdepend 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. It's a similar picture for the Earth, the tropical oceans, which are warmer, have less oxygen than our polar oceans.
 
As interviewed by Wikinews:
Line 29 ⟶ 33:
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 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-->▼
 
'''''(background information):''''' You might wonder why they focus their research on salty solutions. What about fresh water? Well fresh water would work fine too, but it does freeze of course at zero degrees centigrade and in the thin oxygen atmosphere that means less oxygen.
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 {{w|Hygroscopy#Deliquescence|deliquescence}}, and take up water especially easily at low temperatures.▼
 
▲'''''(background information):''''' You might wonder why they focus their research on salty solutions. What aboutAlso 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. MarsIt does have a higher pressure atmosphere at its lowest points such as at the depths of the huge ancient impact crater of the {{w|Hellas Planitia|Hellas basin}},. and this doesThis raiseraises the boiling point of fresh water to 10&nbsp;°C. However, thatbut stillthat means that even there, it is close to boiling point already at 0&nbsp;°C. If any ice melts in the Hellas basin, the water would evaporate away rapidly, indeed the pressure there is so low that ice also isn't stable at that0&nbsp;°C temperatureeither even in the Hellas basin. <!--see Making a Splash on Mars-->
Curiosity discovered indirect evidence of this process 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 when the salts reach temperatures of around -70&nbsp;°C. The 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 -->▼
 
▲However, salty brines can be liquid at well below 0&nbsp;°C, for the same reason salt helps keep roads ice free. Salts,These andsalts very salty brinesalso counteract the tendency of the water to evaporate at low pressures. TheyNot canonly alsothat, salts can take in water from the atmosphere too, in the process known as {{w|Hygroscopy#Deliquescence|deliquescence}}, and take up water especially easily at low temperatures.
 
▲Curiosity discovered indirect evidence of this processdeliquescence in the equatorial regions (through humidity measurements). These regions are so dry that there isn'tis even anyno ice in the surface soil or to considerable depth, yet it found that brines form during winter nights in the top 15cm of the soil when the salts reach temperatures of around -70&nbsp;°C. The 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 -->
 
===The recurring slope lineae===
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. ▼
 
▲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.▼
 
▲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.
[[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. ThereSome areof severalthe 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-->. SomeExperiments in Mars simulation chambers by DLR in Germany found that lichens such as {{w|Pleopsidium chlorophanum}} also may 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.
 
However oxygen rich brines would permit a more energy intensive metabolism and perhaps even true multicellular animal life such as simple sponges. Almost all complex multicellular life uses oxygen.
Line 53 ⟶ 64:
===Lowest oxygen concentrations===
 
'''''Note:''''' The paper usesshows oxygen concentrations in moles per cubic meter. Many otherOther sources usegive the concentrations in miligrams per liter. To convert moles of oxygen per cubic meter to milligrams per litre multiply by 32.
 
Some {{w|Aerobic organism|aerobic}} (oxygen using) microbes can survive with as little as a millionth of a mole per cubic meter (0.000032 mg, or 32 nanograms per liter).
 
Their lowest values are 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 estimatescenario" (where- theythis do the calculations onmeans, their least optimistic assumptions). However, they give reasons for believing that their more optimistic best case calculations are close to the true situation.
 
For calcium perchlorate brines theytheir gotworst case is a level of 2.5 millionths of a mole per cubic meter (0.0008 mg per liter). This can be reached anywhere on Marsa including the tropical southern uplands.
 
Levels 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.
Line 73 ⟶ 84:
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"-->.
 
They paid particular attention to two brines, magnesium and calcium perchlorates, common on Mars. In simulationIf experimentsthey thesestart stayoff liquid, asthey theycan arebe {{w|Supercooling|supercooled}} to temperatures as low as -123 to -133&nbsp;°C before they transition to a glassy state in simulation experiments. They docan thisbe supercooled even when mixed with the soil of Mars (regolith). It's at these very low temperatures that the optimal oxygen concentrations can be reached.
 
ForThe supercooled calcium perchlorate brines, can reach oxygen concentrations high enough for simple sponges 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, oxygen concentrations could go higher, approaching levels typical of sea water on Earth, 0.2 moles per cubic meter (6.4 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 within their 0.2 moles (6.4 mg) per liter.<!-- see for instance the two "Dissolved Oxygen" cites in the Background sources-->. ▼
 
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.
Line 87 ⟶ 97:
 
===Could Mars have creatures as active as our worms and fish?===
 
Wikinews asked him whether their research suggests potential for life as active as the Earth animals that can survive at similar oxygen levels.
[[File:WOA09 sea-surf O2 AYool.png|thumb|Shows how the oxygen dissolved in Earth's sea surface compares with these predicted values for Mars. From the World Ocean Atlas 2009, the values for the annual mean sea surface concentrations range from below 0.2 to above 0.4 moles per cubic meter (6.4 to 12.8 mg / liter). Values on Mars could range up to 0.2 moles per cubic meter for calcim perchlorate, and up to 2 moles per cubic meter for magnesium perchlroate, in extremely cold brines at the poles. {{Image source|Plumbago}}|alt=]]
Line 104 ⟶ 115:
::'''VS''': 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.
 
:: {{WNIQ}} [asked later] When you talked about warm water encountering the brines from below, in our interview - did you have any thoughts about where the water might come from? Geothermal hot spots?
 
::'''VS''': That is possible.
 
'''''(background information)''''': His first suggestion here is that the cool oxygen rich reservoirs could have warmer water come up through them from below. HeIn doesn'tmy sayfollow whereup thequestion warmI waterasked would come from, but one possibility is fromabout geological hot spots. Our orbiting spacecraft have not yet found any, but subsurface hotspots may be hard to spot from orbit, and Olympus Mons has been active as recently as 2.5 million years ago<!-- see for instance Neukum et al in the background sources -->. If sources of warmer water could rise to the surface from below and encounter these cold oxygen-rich brines, life could make use of oxygen where the two mix.
 
The idea then might be that warmer water could rise to the surface from below, heated by the hotspots, and encounter these cold oxygen-rich brines. Then life in the warmer brines could make use of oxygen where the two mix.
 
The other possibility is that microbes can continue to function at very low temperatures in the Martian conditions. After the interview I discovered that they go into this in section ''"3.2 The lower temperature limit for life and the potential of aerobic habitats"'' in the supplementary information.
Line 114 ⟶ 127:
When microbes adapted to extremely cold conditions are cooled down, the interior doesn't freeze but transitions to a glassy state (Intracellular vitrification). This transition is driven by freezing of the external media.
 
From previous research, the brines he studies don't form ice crystals when cooled. Instead, they smoothly transition to a glassy state after supercooling. So,In whenthis way, livinglife in calcium or magnesium perchlorates, with no external crystalization, they could continue to access this from liquid interiors enabling metabolic processes to continue right down to the supercooling limit of the brines. IfIt would depend on whether the cells can keep their intercellular fluids canliquid. stayIf liquidthey can, this will keep the viscosity low, and permit vigorous metabolic processes to continue. EvenIf not, if they enter a glassy state, then even in vitrified cells, metabolic processes continue at a slow pace, but if the fluids stay liquid then fast metabolic processes are possible.
 
[[File:MarsOxides.jpg|thumb|Curiosity's discovery image for the manganese-oxide minerals at a location called "Windjana,". These require abundant water and strongly oxidizing conditions to form. With the new theory these conditions may be present on Mars today, previously thought to be only possible on early Mars.]]
Retrieved from "https://encyclopediaofastrobiology.org/wiki/Special:MobileDiff/10836"