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)
Revision as of 21:01, 6 September 2020
, 3 years agono edit summary
No edit summary |
|||
| (15 intermediate revisions by the same user not shown) | |||
Line 1:
__NOINDEX__
Now published as [[Sponges on Mars? We ask Stamenković about their oxygen-rich briny seeps model]]
Please don't share. For publishing to my own wiki and blog. This article is mid edit. If you spot any errors be sure to say! [[User:Robertinventor|Robertinventor]] ([[User talk:Robertinventor|talk]]) 13:24, 15 December 2018 (UTC)
Line 5 ⟶ 7:
Excluded from search engines
------------------
{{date|
''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,
==Intro==
Line 14 ⟶ 18:
<!-- 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
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 thin atmosphere 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,there's enough oxygen in the brines anywhere on Mars to support microbes that depend on oxygen (aerobes). 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.
Oxygen permits a more energy intensive metabolism, and many microbes and almost all complex multicellular life on Earth depend 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 pf Mars, covering perhaps 6.5% of the Martian surface, oxygen levels 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:
:: '''VS''': Our work really opens up new possibilities for the Martian habitability, and that’s why it’s so exciting!
As previously interviewed by National Geographic (October 22 2018):
::'''Vlada Stamenković''': We were absolutely flabbergasted. I went back to recalculate everything like five different times to make sure it's a real thing.
Line 28 ⟶ 34:
Some background may help before we get to the main interview with Vlada Stamenković.
If you want to go straight to the interview itself, it's here:
* skip to [[#Interview]]
===Why salty water?===
'''''(background information):''''' You might wonder why they focus their research on salty solutions. What about fresh water?
Well, fresh water is likely to be rare on present day Mars. Usually the air pressure is so low that it is not stable even at just above freezing, at 0 °C. The Mars atmospheric is thicker at the depths of the huge ancient impact crater of the {{w|Hellas Planitia|Hellas basin}} and other low points on the surface. This raises the boiling point of fresh water to 10 °C, but that means that even there, it is close to boiling point already as soon as it melts at 0 °C. At that temperature, the water would evaporate away rapidly, indeed the pressure there is so low that ice also isn't stable at 0 °C either even in the Hellas basin. <!--see Making a Splash on Mars-->
However, salty brines can be liquid at well below 0 °C, for the same reason salt helps keep roads ice free. These salts also counteract the tendency of the water to evaporate at low pressures. Not only that, 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 deliquescence in the equatorial regions (through humidity measurements). These regions are so dry that there is no ice in the surface soil. It is also dry to considerable depth, yet the Curiosity team found that brines form during winter nights in the top 15 cm of the soil when the salts reach temperatures of around -70 °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 that 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 Vlada Stamenković and his team's new results, scientists assumed any present day Martian life in these and other habitats would have to be able to grow without oxygen. That leaves many possibilities for Martian life 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-->. Experiments in Mars simulation chambers by DLR in Germany found that lichens such as {{w|Pleopsidium chlorophanum}} may also have some potential to survive in the Mars surface conditions without oxygen. They can do this because the algal component of the lichen 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 ⟶ 68:
===Lowest oxygen concentrations===
'''''Note:''''' The paper
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
Levels in the tropical regions 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.
===Highest oxygen concentrations in their maps===
[[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.]]
[[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 °C, well below its sublimation temperature of -78.5 °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 °C.]]
They
'''''(background information):''''' on Earth, the most oxygen you can get in warm sea water is about 0.28 moles per cubic meter (9 mg per liter) at 20 °C which increasess to 0.34 moles per cubic meter (11 mg per liter) at 0 °C because cold water takes up the oxygen more readily.<!-- see for instance the two "Dissolved Oxygen" cites in the Background sources-->.
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.
This new research greatly expands the possibilities for complex life on Mars.
Line 87 ⟶ 101:
===Could Mars have creatures as active as our worms and fish?===
With this background, Wikinews asked him whether Mars could have life as active as the Earth life that survives 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=]]
:: {{WNIQ|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?
::'''VS''': 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.''
===How could life use oxygen at such low temperatures?===
'''''(background information):''''' Earth microbes live in the slow lane at lower temperatures to the point where individual microbes have lifetimes of millennia. Such life is hard to study. It's almost impossible to tell whether it is
# active and able to reproduce at those temperatures
# active and not able to reproduce, or
# intermittently sometimes active and sometimes dormant.
Researchers can't study the reproduction of such slowly growing cells using cell counts. Perhaps it is possible at lower temperatures, but the usual limit cited is -20 °C<!-- see discussion in A new analysis of Mars "Special Regions" -->. That's well above the lowest Martian temperatures studied in the paper of -133 °C.
Is Martian life able to reproduce below these temperatures?
<!-- This para summarizes the Schulze-Makuch paper in the background information section -->
Dirk Schulze-Makuch
With this background, Wikinews asked:
Line 104 ⟶ 127:
::'''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}} [follow up question] 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.
So one way to have life there could 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 for their paper in a section ''"3.2 The lower temperature limit for life and the potential of aerobic habitats"'' in the supplementary information.
When microbes
[[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.]]
Line 120 ⟶ 145:
===Special minerals on Mars===
'''''(background information):''''' Opportunity discovered manganese oxygens on Mars. These require oxygen to form. Some researchers have suggested they formed in an early Mars atmosphere that was thick and oxygen rich (not necessarily due to life - it could be oxygen rich due to ionizing radiation splitting water).
Their research gives an alternative explanation for these minerals, by concentrating the minute traces of oxygen in the atmosphere into the water.
As previously interviewed by National Geographic (October 22):
Line 233 ⟶ 258:
:: {{WNIQ}} 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?
::'''VS''': 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).''<br><br>''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.
==Background information - history of ideas of oxygen breathing life on Mars==
A historical 101 on multicellular life on Mars may be of interest here. First, of course back in the early twentieth century there was much speculation about oxygen breathing multicellular life there, with Lowell even speculating that intelligent Martians built the canals that he thought he could see in his telescope.
By the time of the first orbital robotic space missions to Mars, it was already clear that the atmosphere was far too thin for terrestrial animals, but there was some hope for plant life. However, the early observations from space showed a barren crater covered land and since then the idea of life on Mars has focused mainly on anaerobic microbes and photosynthetic life.
<!-- For next para: Vera et al in the background information is an example of papers on lichens such as Pleopsidium chlorophanum for Mars and the DLR source gives an overview of their experiments into lichens and blue-green algae-->
In 2014, however, researchers for DLR, Vera et al surprised many astrobiologists with their experimental result that lichens could potentially grow on present day Mars. This is multicellular life, but only in the form of photosynthetic life able to produce its own oxygen. They took some lichens, such as {{w|Pleopsidium chlorophanum}} that were able to survive in close to Mars-like conditions high up on Antarctic mountain ranges, surviving only on the humidity in the air without any water. These did show promise in Mars simulation chamber experiments. They can do this because the algal component is able to make the oxygen needed by its fungal component. They can also do this without needing any extra water as intermediary, in the experiments they are able to grow in partial shade, using only the night time humidity of the atmosphere itself.
It is also possible to have microscopic multicellular animals that can manage without oxygen at all (sub millimeter sized). There are only three species of these creatures known on Earth, however, and they are not candidates for life on Mars. They are three species of {{W|Loricifera#In_anoxic_environment| Loricifera}}, tiny animals about the size of a large amoeba, are able to survive without oxygen in deep extremely salty mud sediments in the Mediterranean.<!--See sources in linked Wikipedia article and: Animals thrive without oxygen at sea bottom in background sources -->
==Background information - why oxygen is so significant for multicellular life==
<!--Note to reviewer - optional section on background information which I thought might help some readers.-->
<!-- summarizes Catling et al from 2014 in background section -->
An oxygen breathing organism can get far more energy from the same amount of food. Without oxygen, the {{w|Glucose|glucose}} that's the source of energy in Earth organisms can only be broken up into two {{w|Pyruvic acid|pyruvate}} molecules (each of 3 carbon atoms). This process produces two molecules of {{w|Adenosine triphosphate|ATP}}, the energy molecule that powers our cells. This is a fast reaction, but the amount of energy it produces is limited. This is the energy production method used in sprinter's "fast twitch" white muscle fibers. When Usain Bolt ran his 100 meters sprint he was relying on this chemical process. He wasn't really using much oxygen, mainly it was using up stores of glucose in his fast twitch muscles.
This is not much use if you want to run a marathon however. Luckily for us, if you use oxygen, glucose can also be reduced all the way to carbon dioxide, and in the process {{w|Cellular respiration#Efficiency of ATP production|30 or 32 ATP molecules}} can be produced from a single molecule of glucose. This is the type of energy production used in the "slow twitch" red muscle fibers of a {{w|Marathon|marathon runner}}, or {{w|Ultramarathon|ultramarathon}} runner. It lets them run for many miles using little by way of glucose from their food. It amounts to about 100 calories in excess over the resting metabolic calories, depending on body mass, or around 25 grams of glucose per mile, which in turn is derived from {{w|Glycogen|glycogen}} and then fat as the race progresses). In this way a large organism can sustain itself with little by way of food if it relies on oxygen.
[[File:Spinoloricus.png|thumb|This tiny animal, which never grows larger than a millimeter in size, is a species of {{w|Loricifera#In_anoxic_environment|loricifera}}, a rare multicellular anaerobe. Shown this colour because it is stained with Rose Bengal. Scale bar is 50 μm. In 2014, Carling et al. showed from general energetic considerations that should also apply to extraterrestrial carbon based life, that it is not easy for a food chain of anaerobes to sustain complex lifeforms even as large as 10 cms in diameter {{Image source|Danovaro et al.}}]]
A lifeform that can't use oxygen needs to eat more than ten times as much food to get the same amount of energy as one that can use oxygen. It is hard for it to grow large because so much food is needed just to sustain itself and for reproduction. On Earth we don't know of any {{w|Anaerobic organism|anaerobes}} (organisms that can manage without oxygen) larger than those three species of {{w|Loricifera#In_anoxic_environment|loricifera}}, which are less than a millimeter in size.
It is possible for microbes to slowly build large structures without breathing oxygen, as with the {{w|Stromatolite|stromatolites}}, which build up layer by layer. However, only the outermost layer, a thin biofilm, is actually alive. Lichens of course do use oxygen, produced by the algal component. Trees and other plants produce oxygen but also use it at night.
What about extraterrestrial life though? Could it use something else in place of oxygen? Well, perhaps, but there is some earlier research that may suggest that it couldn't get very large. In 2005, Catling et al investigated the amount of energy available to carbon based organisms with and without the use of oxygen in their metabolism. Oxygen produces the largest amount of free energy per electron transfer apart from fluorine and bromine, which are too reactive to build up in quantities useful to life. They found on general energetic principles that extraterrestrial life would still needs oxygen to sustain large complex lifeforms, from around 10 cms in size or larger. This is for any extraterrestrial food web for carbon based life.
They worked it out by looking at how many smaller organisms are needed to support larger ones in the food web. For aerobic life the number of organisms in a food web is inversely proportional to the mass, if you are ten times heavier then there are ten times fewer of you in the food web. These numbers are much less for {{w|Anaerobic organism|anaerobes}}.
According to Catling et al's modeling, if an organism is a hundred times larger (and so a million times more massive) in an aerobic food web then it's a million times less numerous (you'd have only one large organism for a million smaller ones).
Meanwhile an organism that's a hundred times larger in an anaerobic food web is a billion times less numerous in an anaerobic food web.
So for instance, if you have a 200 micron organism preying on 20 micron organisms and they in turn on 2 micron organisms then for a billion of the 2 micron organisms there will be a thousand of the 200 micron organisms in an aerobic food chain, but only one in an anaerobic food chain. By the time you get to large organisms of 10 cm scale or larger they should be almost non existent in an anaerobic food web.
If Catling et al are correct in their inference here, then on general energetic principles that an extraterrestrial biosphere with large carbon based animals, at least of 10 cms scale or larger, is going to need oxygen.
Whether or not this applies generally to all extra terrestrial life, it does seem to apply to Earth life. In anoxic environments, Earth animals have found it a challenge to get as large as 1 mm in size without oxygen. It is possible that larger creatures lived on Earth when the seas were all anoxic before the Great Oxygenation Event. There are no surviving multicellular lifeforms from those times but they would be likely to be soft tissued and hard to preserve.
==Technical details - guide to paper==
Line 260 ⟶ 322:
The paper is available to read in its entirety through the link provided on the author's website and the Nature Sharedit sharing initiative.
== Sources ==
| |||