Is there — or was there ever — life on Mars? And will we ever definitively find out? After multiple unmanned missions to Mars, we still can’t answer those questions, but the possibility of life on the Red Planet has intrigued us for decades and our interest in Mars still runs high. Here’s a video produced by the PBS affiliate in San Francisco, California, KQED and their science and environment series QUEST. It looks at our past fascination of Mars and how NASA scientists are hoping the Mars Science Lab rover will help them solve the mysteries of Mars.
18 Replies to “The Question of Life on Mars Still Intrigues Us”
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A great video. how do i get the link for this to share it?
http://www.kqed.org/quest/television/searching-for-life-on-mars
I think we are simply wasting our time on that dead planet. We will never find Martians in a 100 billion years from now. What are we trying to prove anyway ?
We are trying to prove that it is “dead”, or if it is “alive”.
[I am curious/baffled; what did you think?)
This ties into questions of the abiogenesis process, how easy it is and under which conditions it occurs.
It’s not unreasonable to hypothesize that some sort of microbiology exists in the subsoil. Difficult environments for life exist on Earth; yet many organisms find a knish for survival.
Surface geology indicates Mars once had liquid water, and perhaps a thicker atmosphere. These conditions would have been key ingredients for an early Martian ecosystem.
A serious investigations of Mars has the potential of redefining our ideas on how life began in the Solar system.
It’s about time NASA got round to arming the rovers with laser guns. That’ll teach those Martians next time not to mess with our rovers, like they did with poor Spirit. 🙂
It is funny how science fiction had Martians coming to Earth with “heat rays” to blast at us, and now we are sending robots there to zap Maritian geology.
Mars is not a dead planet. It is a bit pokey compared to Earth. It is smaller, less geologically active, it has a much smaller magnetic field, its atmosphere is very thin and so forth. Yet all of that sedimentary rock we find clearly points to a past that had water in a liquid form, which required a much thicker atmosphere to keep water in the liquid phase and probably 3-4 billion years ago Mars was comparable in some ways to Earth at that same time. I think that biochemistry and biology are emergent processes in chemistry which arise naturally, this is not an exceptional “fluke” that is never repeated, and I suspect most scientists with an interest in these things think the same. So it is a quite reasonable hypothesis that life may have originated on Mars, or if there was cross fertilization from Earth to Mars that life on both worlds at least share a common origin. How these explorations will be able to determine one from the other seems very difficult.
There is a prospect that life continues to exist on Mars. I suspect it would exist in the subsoil, where it is shielded from the high UV radiation on Mars and where liquid water can exist on the surface of rock-sand particles. There is evidence of subsurface water from images of apparently liquid pouring out of crater walls. Martian analogues of prokaryotes might continue to exist today. We need to get the analogue of a microbiological and molecular biology lab bench planted on Mars to do these analyses.
LC
LC, if we were to find fossilized microbes or actual life on Mars, how would we go about reconstructing Martian ecological history and our planet’s role in this?
It seems like such a possible discovery would present some very difficult puzzles to deconstruct.
Finding life on Mars is just the beginning. In point of fact the Viking landers did an experiment that put scooped up soil in a heated environment with water and nutrients. The experiment went gangbusters, but the results were retracted because of some issues with the gas chromatography system. The announcement was then that the out-gassing was due to some chemistry with the Martian regolith. I read a few years ago where it was found that the rate of gas production was diurnal, and within an encapsulated system where no sunlight reached the interior. That frankly got me doing some head scratching.
This was during a period where NASA was almost back-pedaling on things, even trying to bury much reference to the moon landings and the rest. This almost sounds as if there was some concerted effort to bury this information. If the gas production was diurnal (day-night cycle) and not exposed to the sun, this might have then been more than a chemical reaction.
Beyond finding life, trying to catalogue the various species (or what ever Martian-clading system one might use) there and building up a catalogue of Martian life, ecosystems and so forth would be a daunting task. If there is life on Mars, then the prokaryotic analogues there in effect modify or control their environment, just as life on Earth has reshaped the landscape here. On Mars it would be more subtle and probably sub-martanean (subterranean on Mars) and there may be a very complex web of life forms.
Trying to find out if life on Mars started independent of Earth life will probably never be satisfactorily answered. If there are some basic biochemical structures and genetics that are radically different from prokaryotes on Earth that might be a sign of independence. Conversely if Martian prokaryotes have copies of many genes and molecular biology found here that might suggest some dependency. Finding life on Mars would be the beginning of a huge astrobiological enterprise — assuming it is financed and we humans do not do some self-extermination routine.
LC
IIRC the isotope ratios of outgassing was put down as caused by Earth chemicals some time ago, the hypothesis was that it was cleaning agents used for the craft. I.e. the previous idea that it was organic molecules reacting with oxidizers like the perchlorates Phoenix discovered is arguable. (I believe the cleaning agent idea was proposed before the perchlorate find, so is now resurrected but on stronger evidence.)
I can’t remember if I ever heard the experiment resulted in diurnal outgassing. But considering the vast temperature differences of the diurnal cycle on Mars surely that variation should be expected of most chemical systems?
“Atmospheric temperatures at the southern landing site (Viking Lander 1) were as high as -14°C (7°F) at midday, and the predawn summer temperature was -77°C (-107°F). In contrast, the diurnal temperatures at the northern landing site (Viking Lander 2) during midwinter dust storms varied as little as 4°C (7°F) on some days.” [“Project Viking Fact Sheet, Courtesy of NASA“]
I can’t find any data on the Viking landers internal climate. (Mostly because the NASA site draaaags like a damaged rover today.)
I would have to research all of this up, but I think the container where the bio-experiment was performed was kept at some constant or ambient temperature and pressure. I don’t remember how the Viking lander powered itself, but I presume it had enough power to heat the container up during the trial. I read a few years ago that there was a diurnal cycle to the gas production.
LC
Fair enough.
It seems reasonable to try to keep temperatures constant/benign. But it could also be reasonable to just change the availability of nutrients as variable, to avoid suppressing/killing off the very life at study.
I doubt that Mars has life, due to the fact it hasn’t taken on different shapes or forms (like it has on Earth), and hasn’t spread across the vast, wide Martian landscape. Here on Earth, life can be found pretty much everywhere, because of billions of years of evolution from single-celled organisms. I’m surprised that Martian micro-organisms (if they exist) haven’t eventually clumped together and formed into multicellular organisms, over the billions of years (I’m assuming) that they should have evolved, and eventually formed vast ecosystems. Today, there seems to be no sign of that having ever happened.
I don’t think anyone expects to find readily visible life, since Mars’ surface is so inhospitable. Due to the thin atmosphere there is a lot of UV radiation, and strong oxidizing agents created by it.
As for multicellularity, if you ask biologists, like all traits this happens with low likelihood. They expect most planets that have life to be unicellular life.
But maybe it isn’t so simple.
Today it is more and more recognized that bacteria evolves multicellular forms in the same way many eukaryotes (cells with nucleus) have done, to make successful spore building forms. And I believe biologists have started to see the same types of signaling and even protein hooks used for cell attachment in prokaryotes (bacteria, archaea) as in eukaryotes.
So maybe it is easier (have larger likelihood) to evolve multicellular traits than believed earlier. Then why don’t bacteria evolve further into large and complex multicellular forms?
It is believed to be due to the difference in energetics between prokaryote and eukaryote cells. Endosymbiosis with bacterial mitochondria ancestors gave eukaryotes a formidable number of power plants, with ~ 10^5 times as much available energy.*
This energy can be used both to evolve a large genome, but more importantly to use it; simply to express the proteins that enables complex traits at a high rate. Complex multicellular forms originated as soon as the atmosphere was oxygen rich enough to support them energetically, or about ~ 0.5 – 1 Gy ago.
And again we see the same thing, endosymbiosis seems to be more frequent than biologists believed earlier. Eukaryote endosymbiosis have been observed many times, and prokaryote endosymbiosis is now known to have happened outside of the mitochondrial event that is believed to have originated eukaryotes.
Prokaryotes are ~ 3.5 – 4.5 Gy old. Eukaryotes are ~ 1.5 – 2 Gy old according to biochemical evidence (fossil steranes). It is then not too surprising if bacteria haven’t happened on the “mitochondrial” endosymbiosis once more. Conversely, maybe many inhabited planets have eukaryote equivalents that can evolve more complex multicellulars at the time they are ~ 2-3 Gy old.
Just in time to take advantage of any oxygen atmosphere any photosynthetic relatives have produced.
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* More exactly, it is the relation between membranes and genomes that enables this.
Mitochondria have large membrane to genome ratio, because most of their genes have been taken over by the eukaryote nucleus over time.
Bacteria can make many copies of their energy producing genes too and can place them at membranes, say by producing many plasmids (bacterial “subsidiary” genomes). But they have no evolutionary pathway handy that would pare down unnecessary genes in plasmids until they happen on the mitochondrial type of system.
A recent documentary (David Attenborough’s First Life) suggests that multicellularity began with the sponges, which utilised the newly available oxygen to creat collagen, the sticky material that can be used to bind cells together.
Either way, it seems an abundance of oxygen is necessary for multicellularity, and the end of the “snowball earth” events have been invoked for causing that oxygen spike (owing to a sudden release of weathered material into the oceans, acting as a sort of massive fertiliser dump for those cyanobacteria producing the oxygen)
Could it be that for Mars to have ever seen multicellularity, a “snowball mars” would need to have happened?
Mars is already an ice ball. Under much of that red-ruddy color are glaciers. LC
Thanks for the response!
Animal multicellularity I believe you mean, plants and fungi are commonly believed to have achieved multicellularity independently. In fact, I recently dug up a reference that observed IIRC 14 (!) different, if not clearly separate, attempts at multicellularity if you include those bacterial forms.
The separation of this is an arguable and researched area.
Last year a sequencing of sponges put them at the base of the clade that leads up to animals, either confirming or inspiring Attenborough. Among other things sponges have the basic tool kits that builds tissues. From genes that makes proteins that hooks cells together, to stuff like genes that produce collagen that cells lays down as an extracellular base layer on which they hook together to build oriented (polarized) epithelial tissue. Interestingly I believe sponges themselves don’t have proper epithelial layers.
Now this heats up because this year an even more basic radiation of slime molds have been found to assemble a functional epithelium! During spore form formation a spore stalk is assembled with a single layer of cells which hooks together and glues to an inner solid core of secreted cellulose + proteins.
I suspect you can discount this as a biologist, but then you have two problems. a) to formulate the usual definition of epithelium to exclude this tissue b) to explain why the same homologous proteins used here later turns up in epithelial tissues.
So perhaps it is too simple to say that multicellularity began at a certain branching of the clade that led up to animals. Maybe the process is much more gradual. (I believe the same gradual assembly of traits is seen in plants now.)
Certainly complex multicellularity doesn’t seem to appear before there were enough oxygen.
Interesting. Collagen as such is proteins making a complex structure that doesn’t seem too clearly known as of yet. [Wikipedia.] I don’t see how that is oxygen dependent.
However, sturdier forms such as bone are collagen mixed with minerals such as hydroxyapatite. Some of those would need an oxygenating atmosphere to form. (I can’t remember if hydroxyapatite does.)
Cellulose as the slime mold uses is produced by cyanobacteria and bacteria in biofilms, so likely predates an oxygenating atmosphere. Maybe that explains the cellulose-collagen switch between slime molds and sponges, the former may predate an atmosphere with high amounts of oxygen.
Personally I take a dim view on the occurence of snowball events. I’ll admit the evidence for at least one slushball seems to be there, both from observation and from modeling. Usually the global glaciations are taken as caused by atmosphere changes and not vice versa.
Today ocean fertilization means absence of oxygen because of the explosion of poisonous oxygen-consuming cyanobacteria (ironically enough), so I dunno what to make of that at the moment. I have to catch up on those ideas.
What they see in the Lantian biota (early Edicarian, just after the Cryogenian @ 635 My, as old as 614-635 My) is shallow water forms (but below the storm base). They differ distinctly from the later deep water Avalon biota (579 to 565 million years old). [“An early Ediacaran assemblage of macroscopic and morphologically differentiated eukaryotes”, Yuan et al.]
They also indicate that some of the purported anoxic deep water conditions of Edicarian is at least of temporary character:
“To reconcile the conflicting geochemical and palaeontological
indicators of palaeoredox conditions, we propose that the Lantian
basin was largely anoxic but punctuated by brief oxic episodes. These
oxic episodes were opportunistically capitalized on by benthic macroeukaryotes
that were subsequently killed and preserved by frequent
switch-backs to anoxic conditions. Brief oxic intervals also occurred in
many Mesozoic anoxia events27, and they are consistent with existing
geochemical data from other Ediacaran basins suggesting significant
temporal and spatial variations in redox conditions despite overall
anoxia11,24,26,28,29. This more complex picture of Ediacaran ocean redox
history calls for integrated geochemical, palaeontological and sedimentological
investigations at ultrahigh stratigraphic resolution.”
The earliest Eukaryotes, such as protistans, came about 2 billion years ago, and the earliest multicellular life probably about 7-800 mya. Eukaryotes as assemblies of prokaryotes recruited in prokaryotes which served as cellular respiration machines, called mitochondria, and were able to amplify their energy use. Plants of course recruited in a form of blue-green algae (prokaryotes) which are chloroplasts. In the preCambrian period multicellular life began to evolve into echinoderms, tunicates and other forms.
On Mars such complexity is not likely to evolve, or if it did in the past it has probably been pushed to extinction.
LC