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Science Forum

  1. Standard member sonhouse
    Fast and Curious
    15 Jun '10 04:04
    http://www.sciencedaily.com/releases/2010/06/100613181245.htm

    A large ocean 1/3 the surface area of Mars existed about 3 billion years ago, I guess about the time life was getting good and started on Earth. My question would be how long it remained a large ocean and if the conditions were ripe for life on Earth and Mars.

    How advanced could life have evolved on Mars, given a large ocean which by definition implies a surface temperature above freezing and with enough surface air pressure to allow liquid water without evaporation for long periods of time, the question being, a few million years?

    100 million years? A lot can happen evolution wise in that much time so there might be fossil organisms found a lot higher on the food chain than just microbes which is the present conservative take by the scientific community.

    If life were to be found there at all, fossil life that is, it would according to present thought, only be microbes. But if a large ocean was present for hundreds of millions of years there may be actual multicellular fossils as well, maybe like Earth life 500 million years ago.

    It would be incredible if some future Mars manned expedition found life of ANY kind underground, just for the analysis of what it would have in the way of DNA or whatever the analogue would have been on Mars, presumably given an independent evolution of life there.

    If they found something like our style of DNA, that would be a large hint that Panspermia theories were right! All speculation now of course.
  2. 15 Jun '10 05:54
    Originally posted by sonhouse
    How advanced could life have evolved on Mars, given a large ocean which by definition implies a surface temperature above freezing and with enough surface air pressure to allow liquid water without evaporation for long periods of time, the question being, a few million years?
    Having only one example, we really don't know very much about how long it takes life on average to go complex.
    On earth, it took a very long time for life to go from single cellular to complex multicellular.
  3. 15 Jun '10 06:11
    Originally posted by sonhouse
    If they found something like our style of DNA, that would be a large hint that Panspermia theories were right! All speculation now of course.
    Panspermia, or interplanetary transportation by meteors. How could we know which?
  4. Standard member sonhouse
    Fast and Curious
    15 Jun '10 16:39
    Originally posted by FabianFnas
    Panspermia, or interplanetary transportation by meteors. How could we know which?
    If panspermia is the correct theory, then more data would come in from life forms found on say, Titan, or Europa. If the meteorite theory is correct, then we will find life with maybe DNA similar to Earth life on Mars, and it would be another tale figuring out which came from where, meteorite hitting Mars with Earth life or vice versa.

    If panspermia is the true story, then we would most probably find Earthy kind of DNA stuff on Titan, Europa, etc., and maybe other moons with internal heat and liquid water.
    Of course we would not live long enough to see that news, I imagine that will have to wait till late 21st century or 22nd century, assuming our civilization lasts at a high technological level that long (global warming, wars, disease, whatever, stopping our civilization from being able to have a space program, an ice age, something like that and we are out in the cold so to speak, spacewise, too busy covering our assses on Earth to go back into space)
  5. Standard member avalanchethecat
    Not actually a cat
    15 Jun '10 19:39
    Or, just maybe, the development of life based on nucleic acids is not an unlikely occurrence given the right conditions.
  6. Standard member sonhouse
    Fast and Curious
    15 Jun '10 22:31
    Originally posted by avalanchethecat
    Or, just maybe, the development of life based on nucleic acids is not an unlikely occurrence given the right conditions.u
    But the real question to be answered would be if that were the case, would independent life starting up on some other star system on and Earth-like planet end up with our style of DNA or are there other forms of what we call DNA, maybe with a double helix or three stranded helix or something totally off the wall. The thing about DNA and genes is they have to have a heck of a lot of information stored in a very tiny space and there may be only a few methods available to biology to do that. Or not
    It's just that our DNA would stretch out a few feet if unwound all the way and any complex life form would presumably have to have a similar amount of information stored and ready to use in biological systems, however that would turn out to work when we get to those other planets to analyze that stuff.

    For instance, you see morning glories that have the ability to curl around branches and such, and it is the same with DNA, all curled up, so maybe that is a common feature of all life forms. It would make sense to have DNA style information stored in as dense a format as possible.

    It may be just luck that ended up with our style of double helix DNA, maybe others will have triple helix or quad helix, but curled up seems the best way to go about it.
  7. 17 Jun '10 00:14
    hopefully they'll send some fossil-oriented missions now.
  8. 17 Jun '10 00:17
    Originally posted by sonhouse
    But the real question to be answered would be if that were the case, would independent life starting up on some other star system on and Earth-like planet end up with our style of DNA or are there other forms of what we call DNA, maybe with a double helix or three stranded helix or something totally off the wall. The thing about DNA and genes is they have t ...[text shortened]... e others will have triple helix or quad helix, but curled up seems the best way to go about it.
    http://en.wikipedia.org/wiki/Origin_of_life#Origin_of_organic_molecules

    ...

    Models to explain homochirality

    Main article: Homochirality ( http://en.wikipedia.org/wiki/Homochirality )

    Some process in chemical evolution must account for the origin of homochirality, i.e. all building blocks in living organisms having the same "handedness" (amino acids being left-handed, nucleic acid sugars (ribose and deoxyribose) being right-handed, and chiral phosphoglycerides). Chiral molecules can be synthesized, but in the absence of a chiral source or a chiral catalyst, they are formed in a 50/50 mixture of both enantiomers. This is called a racemic mixture. Clark has suggested that homochirality may have started in space, as the studies of the amino acids on the Murchison meteorite showed L-alanine to be more than twice as frequent as its D form, and L-glutamic acid was more than 3 times prevalent than its D counterpart. It is suggested that polarised light has the power to destroy one enantiomer within the proto-planetary disk. Noyes[53] showed that beta decay caused the breakdown of D-leucine, in a racemic mixture, and that the presence of 14C, present in larger amounts in organic chemicals in the early Earth environment, could have been the cause. Robert M. Hazen reports upon experiments conducted in which various chiral crystal surfaces act as sites for possible concentration and assembly of chiral monomer units into macromolecules.[54] Once established, chirality would be selected for.[55] Work with organic compounds found on meteorites tends to suggest that chirality is a characteristic of abiogenic synthesis, as amino acids show a left-handed bias, whereas sugars show a predominantly right-handed bias.[56]

    ...
  9. Standard member sonhouse
    Fast and Curious
    17 Jun '10 13:11
    Abiogenesis: In case anyone wants to know just what that is.

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

    Note that this is distinct from evolutionary theories, evolution having to do with what happens to lifeforms after life has gotten started. Evolution does not try to say what started life in the first place.