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Thread: Mars used to have life...

  1. #1 Mars used to have life... 
    Forum Bachelors Degree x(x-y)'s Avatar
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    Evidence suggests that Mars may have had life at some point in the past. The difference between Earth and Mars is that during formation, Earth's inner core of solid iron and nickel with an outer core of other hot metals moving fairly quickly created a strong magnetic field which shielded (and shields) the atmosphere from being bombarded with cosmic and solar radiation, which prevents the atmosphere from being stripped away rapidly... Mars on the other hand doesn't have a strong magnetic field and so this led to rapid deterioration of it's atmosphere.

    Now, Mars has a very thin atmosphere comprised mostly of CO2 (98%) which is, obviously, not a good support for life. However, scientists have reason to believe that before a lot of Mars' atmosphere was stripped away, life could've been present there due to conditions which would be similar to Earth's. You may ask how this could be as Mars is not in the habitable zone of our solar system and so water should've taken a solid (ice) form on the surface. However, Mars has a much higher % of CO2 in it's atmosphere than Earth, which gives us reason to suggest that it had a high % in the past too. This means that the greenhouse effect upon the planet's lower atmosphere (troposphere) and surface would be much greater than here on Earth. This would compromise for the less solar radiation reaching the planet and would've made it much warmer- about Earth's average surface temperature (15°C). So water would've been able to take a liquid form on the planet's surface which is the staple ingredient for supporting life! Additionally, we know that the compounds and elements contained within the soil from Mars suggests past life- carbon compounds etc.

    Thanks for reading!

    All critiscm and comments appreciated! But please go easy, I'm only 16 and starting my A-levels very soon (Chemistry, Physics, Maths and Geography if you were wondering)...

    - x(x-y)


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    I am from the school of thought that supposes there is still life on Mars.

    We know the erosive effect of the solar wind acting on an atmosphere unprotected by a magnetic field has removed a substantial portion of Mars's early atmosphere. A further large part of that atmosphere is trapped in solid carbon dioxide, primarily at the poles.

    We also know that the early Mars had a powerful magnetic field. (The residual magnetism found in parts of the Martian crust are a couple of orders of magnitude greater than comparable terrestrial magnetism.)

    Conseqeuntly, on these facts alone there is every reason to believe that early Mars was warm and potentially wet. That potential is shown to be a reality by such features as the water eroded Valles Marineris, or the shorelines of the Northern Sea.

    If life arises naturally under the right conditions then the right conditions were present on early Mars just as they were on early Earth. So, given that intial if, life would have gained a foothold.

    Then, we look at the range of environments in which life can exist on Earth - I'm thinking of the extremophiles - and it would be surprsing if life had not persisted somewhere on Mars.

    I go a step beyond that and lean towards the notion that the Viking craft detected life there in the 1970s. I find the counter arguments overly contrived.


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    Yes, interesting. I never knew Mars had a particularly strong magentic field in it's early stages, but if so then that means Mars' may have had life for quite a long time before it died out- it may have had basic intelligent life forms...

    I believe that Mars probably still has single cell organisms buried in it's soils and maybe varieties of multi-cellular organisms. These may get the warmth they need from the ground (convectional heating) and the moisture may still be present in small quantities in the ground too.

    There are some theories that much of the past life on Mars burrowed underground as conditions became worse, and that even some small mammals may be burrowed underground on Mars today. Do you agree with this?
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    Quote Originally Posted by x(x-y)
    There are some theories that much of the past life on Mars burrowed underground as conditions became worse, and that even some small mammals may be burrowed underground on Mars today. Do you agree with this?
    No. I would completely disagree. Mars retained habitable surface conditions for only a few hundred million years after the Heavy Bombarment phase. This was arguably enough time for life to emerge, but no time at all to allow even single celled eukaryotes to evolve. That took a billion and a half years or more on Earth.

    There is no way I can envisage that highly complex lifeforms could have evolved and certainly not intelligent creatures and asolutely not mammals.

    I do not discount the possibility that a prokaryote like life form could have evolved eventually into something somewhat more complex, but the paucity of the environments would have limited the degree of complexity. So sadly no subterranean voles burying under Hellas Planita.
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    I agree. I see no way that mammals could have come into existence on Mars given the small time period that you stated. However, I do believe that single celled organisms exist on Mars today within the ground- but no mammals due to the reasons you stated.

    What was the first life on Earth? It was the stromatalites wasn't it? But they died out (mostly) after the Snowball Earth scenario... I think...
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    Stromatolites are still around today - Shark Bay, Australia.

    http://en.wikipedia.org/wiki/Stromatolite

    Life on Earth probably began on undersea hydrothermal vents. Possibly on Mars, too.

    http://en.wikipedia.org/wiki/Hydrothermal_vent
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    Quote Originally Posted by x(x-y)
    What was the first life on Earth? It was the stromatalites wasn't it? But they died out (mostly) after the Snowball Earth scenario... I think...
    Stromatolites are already quite advanced, so I doubt they were the first life. They were the first life of which we have clear cut evidence.
    That's not strictly true either - oxygen isotope ratios in the Issua Formation in Greenland suggest biological activity at a time predating the first stromatolites.
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    Ok, actually I must've got it wrong...

    Stromatolites were the first species to 'dominate' the planet, that's probably what I meant...
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    Quote Originally Posted by x(x-y)
    Ok, actually I must've got it wrong...

    Stromatolites were the first species to 'dominate' the planet, that's probably what I meant...
    You didn't exactly have it wrong. It's the sort of comment that gets made in science documentaries: it's aesthetically valid, sort of true, but scientifically imprecise.

    Geo,
    I'm not a great fan of the hydrothermal vent - origin of life approach. It smacks too much of jumping on a fashionable bandwagon. I remain wedded to the notion of pan spermia, largely because it is unconventional.
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    Quote Originally Posted by Ophiolite
    I remain wedded to the notion of pan spermia, largely because it is unconventional.
    That's hardly science!
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    I agree with the theory that life on Earth originally came from hot, nutrient rich springs and volcanic lakes. This is because we have seen that there is life in these places today- micro-organisms- which is a very likely place that life could've started and evolved from. However, life may have also been present in hydrothermal vents at, or near to, that time. The theory of life starting on Earth from an asteroid impact, I find hard to agree with, yet I have not seen all the evidence...
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    I think if life ever did develop and evolve on Mars, it probably found a way to survive, even if deep under the surface.

    With a sample size of one, I don't think we really have any idea how long it takes life to evolve from one stage to another. Even on our planet, the majority of life's diversification seems to have happened over the past half a billion years.

    One thing that always confounded me a bit was the idea that the sun's solar wind was much stronger in the past, even though the total radiance of the sun is thought to have been as much as 30% lower.
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    Quote Originally Posted by Ophiolite
    I am from the school of thought that supposes there is still life on Mars.


    If life arises naturally under the right conditions then the right conditions were present on early Mars just as they were on early Earth. So, given that intial if, life would have gained a foothold.

    Then, we look at the range of environments in which life can exist on Earth - I'm thinking of the extremophiles - and it would be surprsing if life had not persisted somewhere on Mars.
    Probably there is still primitive life on Mars.
    I do believe life, of some kind, is inevitable if a planet has the conditions that allow matter to combine in ever more complex forms.
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    Life began on Earth at least 2.8 billion years ago. That represent the oldest unequivocal evidence of life. There are, as has been mentioned earlier, deposits (in Western Australia) which some scientists have interpreted as stromatolites, and which have been dated at 3.6 billion years ago. However, those deposits could also quite easily have been abiotic.

    There are, in Greenland, some traces of organic matter, dated 3.8 billion years ago. If this represents life, it is the oldest detected. However, there is no clear evidence that these traces came from living things. They could quite easily have been from abiotic processes also.

    Either way, the earliest life detectable from traces on Earth would have arisen no earlier than 700 million years after the sterilising asteroid bombardment that resulted in the moon. It is quite possible that it might have taken 1.7 billion years from that bombardment for life to arise.

    As far as Mars is concerned, I am seriously sceptical of the idea that life began and evolved there. The time when there was an adequate atmosphere, and warm liquid surface water, represents a period of some few hundreds of millions of years only. The evidence on Earth suggests that life took longer than that to appear here. So why should we believe life could come into existence and evolve on Mars in such a short time?

    My own view is that, if we find life on Mars, it is more likely to be bacteria related to Earth bacteria. We know that a massive asteroid impact on the Earth, like the one that killed the dinosaurs, is enough to flick Earth rock into space, and even escape the Earth's gravity. Certain bacterial spores are tough enough to survive the accelerations, and the cold, vacuum and radiation of space. If a rock carrying bacterial spores landed on Mars, it could seed that planet with Earth bacteria. This might have happened 65 million years ago.

    However, only exploration and testing of Mars material will give us the answer.
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    Interesting theory, skeptic.

    But even if micro-organisms (such as bacteria and viruses) developed on Mars, that is still life no matter how basic it is. Also how could certain 'spores' survive on a rock travelling (at a high velocity) through space towards Mars? Spores can generally only withstand a temperature of up to 120°C before being 'destroyed'- and temperatures would get way above that mark on an unprotected rock in full sunlight. Additionally, even if the spores did survive, surely they would be destroyed by great heat upon impact with the surface of Mars?
    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
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    Quote Originally Posted by x(x-y)
    Spores can generally only withstand a temperature of up to 120°C before being 'destroyed'- and temperatures would get way above that mark on an unprotected rock in full sunlight.
    But not in the rock.

    Quote Originally Posted by x(x-y)
    Additionally, even if the spores did survive, surely they would be destroyed by great heat upon impact with the surface of Mars?
    Not at all. The interior of meteorites that have lost 50% of their mass through ablation coming through the Earth's atmosphere are still well below zero Celsius.

    More relevant is the survival of the impact that ejects them. This has been modelled for the Mars impacts and there is no problem.
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    And my idea could well be so much bulldust. I explored a possibility. Whether it is a reality is just speculation. The data we have on bacterial spores and the conditions they would have to face to travel to Mars via space rock suggest the possibility, but no more.

    Interestingly, bacterial spores have been recovered (according to New Scientist mag) and incubated in culture media, from the interior of rock that is millions of years old. There is a very real possibility that bacterial spores can stay viable for extreme lengths of time. So spores inside a rock drifting in space could possibly survive eons.

    Once a spore finds itself on Mars, it will need liquid water to develop into a viable bacterium. However, it does not need much. In Antarctica, on a microscopic level, rocks may have a thin film of liquid water under them, even though they are surrounded by ice at minus 50 C. It is not too much to conceive of a thin zone around a Mars rock with a little liquid water - enough to allow a spore to germinate and then reproduce.
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    Ah, ok, inside the rock would make more sense, I suppose.
    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
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