Good question. Yes conceivably. First, there are many possible types of habitats on Mars. And some of those habitats are quite isolated from each other.
Also the surface has been largely frozen and water free for millions of years, long enough for life there to be thoroughly sterilized in the surface layers in any place that isn't a habitat.
On the other hand though, we have the Martian global dust storms. Those block out 99% or more of the sunlight when the storms are at their darkest, and can do that for weeks on end. Here 4.7 corresponds to 99% blocked
The dust is iron rich and Carl Sagan noted long ago that microbe spores, if they are imbedded in a grain of Mars dust, could potentially be carried by the dust storms anywhere on Mars.
So, for hardy microbes able to survive on the surface in spore form - the dust storms protect them from UV light and the cosmic radiation just doesn't do enough damage over timescales of up to a few hundred thousand years to be a limiting factor.
So - Are the surface habitats isolated from each other or not?
It's anybody's guess at present.
The habitats themselves are, (if they exist at all) most of them, not on the surface, but a few mms below the surface or up to a cm or so below the surface. Some may be below the surface of rocks or half a meter or so down in an ice sheet. Or inside deposits of salts.
There's also the possibility of life that could survive directly on the surface
I think we can suppose any of these hypotheses for the surface habitats:
It might also have deep hydrosphere kilometers below the surface.
Again any of those habitats could be
They could remain dormant for hundreds of millions of years and revive, and possibly still be able to reproduce. And older microbes from billions of years ago, in ideal conditions, could still be recognizable so that we can tell what the life was like and what its organic chemistry was like. This is something that is pretty much impossible on the Earth.
Now - all these forms of life are likely to be quite hard to find. Present day life because the conditions are so harsh. Even in the beset habitats, then the life may exist only in tiny populations, very sparse, slow growing, even with individual microbes with lifetimes of thousands of years (because that is what happens in the most similar habitats on the Earth).
Past life may have been abundant - or may have always been scarce. Conditions more habitable - but did it evolve enough to take advantage of them? If it did - still there is the problem of preservation. Just as fossils are hard to find on the Earth - ancient fossils on Mars - which are just traces of organics trapped in mud and salt - they may be hard to find also. Easily washed out by later floods, or eaten by later microbes. Or if brought to the surface, then damaged by cosmic radiation. Or if kept in warm conditions, the organics change due to "racemization" and are hard to recognize as created by life.
If there was or is life on Mars I'm sure we will find it eventually. On such a large planet as large as the surface area of Earth, and such diverse geology we are bound to get conditions that lead to preservation of ancient life somewhere or other - especially since it is so cold and no continental drift.
But - shouldn't be surprised if our first few explorations of Mars searching for life turn up a blank. It could just mean we haven't yet discovered the right place to search for it.
And I think it is totally possible that there could be separate populations of species in different habitats. And some may be native Mars, some Earth, maybe some are a mix of both co-existing. And some could be not quite yet life. Potentially with subsurface caves especially, don't see why you couldn't have all of those on the same planet. Because as you say - the surface is so inhospitable over most of it, that it would help to create islands of habitability like this.
But we don't know enough to say either way at present, just many guesses.
See also:
Where To Search On Mars For Droplets, & Shallow Flows Of Liquid Water - Where Microbial Life May Flourish
Also the surface has been largely frozen and water free for millions of years, long enough for life there to be thoroughly sterilized in the surface layers in any place that isn't a habitat.
On the other hand though, we have the Martian global dust storms. Those block out 99% or more of the sunlight when the storms are at their darkest, and can do that for weeks on end. Here 4.7 corresponds to 99% blocked
So, for hardy microbes able to survive on the surface in spore form - the dust storms protect them from UV light and the cosmic radiation just doesn't do enough damage over timescales of up to a few hundred thousand years to be a limiting factor.
So - Are the surface habitats isolated from each other or not?
It's anybody's guess at present.
The habitats themselves are, (if they exist at all) most of them, not on the surface, but a few mms below the surface or up to a cm or so below the surface. Some may be below the surface of rocks or half a meter or so down in an ice sheet. Or inside deposits of salts.
There's also the possibility of life that could survive directly on the surface
I think we can suppose any of these hypotheses for the surface habitats:
- All the habitats are inhabited, with the same mix of species because of the mixing of the dust storms
- Only a few of the habitats are inhabited, by the same species, rest are uninhabited, and life gradually spreads to them but it takes a long time after a habitat first appears for life to spread to it
- Most or all the habitats are inhabited, same species
- The habitats are inhabited by many different species and due to isolation they don't mix much
It might also have deep hydrosphere kilometers below the surface.
Again any of those habitats could be
- Inhabited by life related to Earth life
- Uninhabited
- Inhabited by native Mars life unrelated to Earth life
- Related to Earth life but its last common ancestor is billions of years ago, and the cells are simpler than Earth life or followed a different path of evolution
- Has complex chemistry and proto cells that are on their way towards life but are not yet alive as we currently understand it.
They could remain dormant for hundreds of millions of years and revive, and possibly still be able to reproduce. And older microbes from billions of years ago, in ideal conditions, could still be recognizable so that we can tell what the life was like and what its organic chemistry was like. This is something that is pretty much impossible on the Earth.
Now - all these forms of life are likely to be quite hard to find. Present day life because the conditions are so harsh. Even in the beset habitats, then the life may exist only in tiny populations, very sparse, slow growing, even with individual microbes with lifetimes of thousands of years (because that is what happens in the most similar habitats on the Earth).
Past life may have been abundant - or may have always been scarce. Conditions more habitable - but did it evolve enough to take advantage of them? If it did - still there is the problem of preservation. Just as fossils are hard to find on the Earth - ancient fossils on Mars - which are just traces of organics trapped in mud and salt - they may be hard to find also. Easily washed out by later floods, or eaten by later microbes. Or if brought to the surface, then damaged by cosmic radiation. Or if kept in warm conditions, the organics change due to "racemization" and are hard to recognize as created by life.
If there was or is life on Mars I'm sure we will find it eventually. On such a large planet as large as the surface area of Earth, and such diverse geology we are bound to get conditions that lead to preservation of ancient life somewhere or other - especially since it is so cold and no continental drift.
But - shouldn't be surprised if our first few explorations of Mars searching for life turn up a blank. It could just mean we haven't yet discovered the right place to search for it.
And I think it is totally possible that there could be separate populations of species in different habitats. And some may be native Mars, some Earth, maybe some are a mix of both co-existing. And some could be not quite yet life. Potentially with subsurface caves especially, don't see why you couldn't have all of those on the same planet. Because as you say - the surface is so inhospitable over most of it, that it would help to create islands of habitability like this.
But we don't know enough to say either way at present, just many guesses.
See also:
Where To Search On Mars For Droplets, & Shallow Flows Of Liquid Water - Where Microbial Life May Flourish
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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