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If life - present or past - is one day found on Mars, I shall be hugely surprised if it doesn't share our basic DNA. Interplanetary pollution - pollination, if

If life - present or past - is one day found on Mars, I shall be hugely surprised if it doesn't share our basic DNA. Interplanetary pollution - pollination, if you will - or common influx from somewhere entirely else.

karmakaze 8y ago
History repeats itself. So many times a group of people on earth thought they were alone (a tribe, a region, an island, a continent), they were wrong. Earth is our current island, scale it up. Chances are when we find other life, it will share a common source with us. There's likely other life that doesn't but the closer ones probably do.
- everdev 8y ago
  Maybe we are the "uncontacted tribe". I wonder at what point when you're observing an isolated tribe do they demonstrate enough advances that it's OK to contact them? Or do you just wait until they discover the observer?
  - bluGill 8y ago
    I doubt we are observed. Space is really really big - even bigger than that... Are first radio signals have barely reached 100 light years by now (you a great antenna to received them). All other intelligent beings know about earth is what they can infer from how our gravity changes the sun, and other such indirect measures.
  - karmakaze 8y ago
    If we're not currently odds are we will be--given N tribes, we're only 1.
Symmetry 8y ago
On the other hand we haven't been able to establish a firm minimum amount of time from when Earth got oceans to when it got life. It took a long, long time to add photosynthesis to cemosynthesis, a long long time to create eukaryotes, and a long, long time to create multicellular life. I made a timeline: http://hopefullyintersting.blogspot.com/2018/03/the-drake-equation-again.html http://hopefullyintersting.blogspot.com/2018/03/the-drake-eq... Interplanetary pollution seems to happen pretty quickly compared to the history of life but I'm not sure we can say that it happens quickly compared to the start of life. Of course for all we know the reason Earth developed life so quickly was that it was seeded by the quicker-cooling Mars which had had Oceans before Earth did. More research is needed!
- interfixus 8y ago
  I would not presume to have any opinion on the direction such traffic might have taken. All I know is the one certain, observed fact in this case is that pieces of Mars have indeed fallen to the surface of Earth. There is of course no known reason why the reverse would not have happened. From your writings (added to feed, thank you) I notice we share a belief: That life may well be quite common out there, but human level intelligence exceedingly rare. I somehow believed this from a very young age, long before I ever heard of Drake or his equation or any such calculation.
rootbear 8y ago
I was just reading about how far out into space the ejecta from the Chicxulub impact went and it really brought home how possible it is that life from Earth migrated elsewhere, Mars being an obvious possible destination. But as one gets further out, it seems less and less likely that any life found has terrestrial origins. I am very much interested in knowing if there is any independently evolved life in the oceans of Europa or any of the other ice moons.
- everdev 8y ago
  Space is pretty inhospitable though. Is it possible for living organisms to survive ejection, a space journey and re-entry?
  - rootbear 8y ago
    It's an open question, but there is some reason to believe that bacteria can survive a journey through space. Multicellular life would be much less likely to survive, although I'm constantly amazed at how hard it is to kill a tardigrade!
    - mda 8y ago
      Long journey to Mars in hard vacuum and under UV radiation makes it very unlikely, but bacteria spores are very resilient to harsh conditions. I think it is still theoretically possible. There are a few papers on this. https://www.ncbi.nlm.nih.gov/m/pubmed/11539977/ https://www.ncbi.nlm.nih.gov/m/pubmed/11539977/
    - sureste 8y ago
      It's called panspermia, for the curious.
    - dustfinger 8y ago
      A tardigrade must first complete cryptobiosis, otherwise they are fragile[1]. Given that it takes time to enter cryptobiosis (maybe 1 hour), it is unlikely that any active tardigrade would survive a meteor impact. Suppose a tardigrade was in complete cryptobiosis and survived a journey to the surface of Mars. Conditions would need to be favorable if it were to ever regain an active metabolic state. [1]https://www.quora.com/What-does-it-take-to-kill-a-waterbear-tardigrade https://www.quora.com/What-does-it-take-to-kill-a-waterbear-...
kylek 8y ago
We're aware of meteorites from Mars coming to Earth (a quick search brings up [0]) - who says they can't go the other way! [0] https://www.space.com/14268-rare-mars-meteorite-rocks-tissint.html https://www.space.com/14268-rare-mars-meteorite-rocks-tissin...
jerf 8y ago
If life is discovered on Mars, I'm going to be waiting to see if it is obviously Earth-based DNA. If so, then as excited as people will be, it won't actually be any particular sort of evidence for wide-spread life. It'd still probably be a reasonable candidate for discovery of the century, but not the millenium. (We will be able to determine if it is has the same source as Earth-based life, because Earth-based life has a lot of things that seem like they ought to be free parameters, but are highly conserved across our entire ecosystem. This includes certain basic genes and processes and their exact "spelling" in genes, the mapping of DNA letters to proteins, and probably quite a few other things. Can't disprove a common third source that way, of course.)
- jbattle 8y ago
  Or ... do we have Mars-based DNA?
  - jerf 8y ago
    I've seen the theory tossed out there, but it's hard to do anything about it. We'd need paleontologists on Mars to really be sure (to prove life that predates Earth, as a step 1), and we're a long way away from that no matter how you slice it. But as I understand it, the time scales work; for the same reason that Mars is basically a dried-up, used up planet now while Earth is flourishing with life, Mars was theoretically possibly habitable much earlier than Earth.

karmakaze 8y ago

History repeats itself. So many times a group of people on earth thought they were alone (a tribe, a region, an island, a continent), they were wrong. Earth is our current island, scale it up. Chances are when we find other life, it will share a common source with us. There's likely other life that doesn't but the closer ones probably do.

everdev 8y ago
Maybe we are the "uncontacted tribe". I wonder at what point when you're observing an isolated tribe do they demonstrate enough advances that it's OK to contact them? Or do you just wait until they discover the observer?
- bluGill 8y ago
  I doubt we are observed. Space is really really big - even bigger than that... Are first radio signals have barely reached 100 light years by now (you a great antenna to received them). All other intelligent beings know about earth is what they can infer from how our gravity changes the sun, and other such indirect measures.
- karmakaze 8y ago
  If we're not currently odds are we will be--given N tribes, we're only 1.

Symmetry 8y ago

On the other hand we haven't been able to establish a firm minimum amount of time from when Earth got oceans to when it got life. It took a long, long time to add photosynthesis to cemosynthesis, a long long time to create eukaryotes, and a long, long time to create multicellular life. I made a timeline: http://hopefullyintersting.blogspot.com/2018/03/the-drake-equation-again.html http://hopefullyintersting.blogspot.com/2018/03/the-drake-eq... Interplanetary pollution seems to happen pretty quickly compared to the history of life but I'm not sure we can say that it happens quickly compared to the start of life. Of course for all we know the reason Earth developed life so quickly was that it was seeded by the quicker-cooling Mars which had had Oceans before Earth did. More research is needed!

interfixus 8y ago
I would not presume to have any opinion on the direction such traffic might have taken. All I know is the one certain, observed fact in this case is that pieces of Mars have indeed fallen to the surface of Earth. There is of course no known reason why the reverse would not have happened. From your writings (added to feed, thank you) I notice we share a belief: That life may well be quite common out there, but human level intelligence exceedingly rare. I somehow believed this from a very young age, long before I ever heard of Drake or his equation or any such calculation.

rootbear 8y ago

I was just reading about how far out into space the ejecta from the Chicxulub impact went and it really brought home how possible it is that life from Earth migrated elsewhere, Mars being an obvious possible destination. But as one gets further out, it seems less and less likely that any life found has terrestrial origins. I am very much interested in knowing if there is any independently evolved life in the oceans of Europa or any of the other ice moons.

everdev 8y ago
Space is pretty inhospitable though. Is it possible for living organisms to survive ejection, a space journey and re-entry?
- rootbear 8y ago
  It's an open question, but there is some reason to believe that bacteria can survive a journey through space. Multicellular life would be much less likely to survive, although I'm constantly amazed at how hard it is to kill a tardigrade!
  - mda 8y ago
    Long journey to Mars in hard vacuum and under UV radiation makes it very unlikely, but bacteria spores are very resilient to harsh conditions. I think it is still theoretically possible. There are a few papers on this. https://www.ncbi.nlm.nih.gov/m/pubmed/11539977/ https://www.ncbi.nlm.nih.gov/m/pubmed/11539977/
  - sureste 8y ago
    It's called panspermia, for the curious.
  - dustfinger 8y ago
    A tardigrade must first complete cryptobiosis, otherwise they are fragile[1]. Given that it takes time to enter cryptobiosis (maybe 1 hour), it is unlikely that any active tardigrade would survive a meteor impact. Suppose a tardigrade was in complete cryptobiosis and survived a journey to the surface of Mars. Conditions would need to be favorable if it were to ever regain an active metabolic state. [1]https://www.quora.com/What-does-it-take-to-kill-a-waterbear-tardigrade https://www.quora.com/What-does-it-take-to-kill-a-waterbear-...

kylek 8y ago

We're aware of meteorites from Mars coming to Earth (a quick search brings up [0]) - who says they can't go the other way! [0] https://www.space.com/14268-rare-mars-meteorite-rocks-tissint.html https://www.space.com/14268-rare-mars-meteorite-rocks-tissin...

jerf 8y ago

If life is discovered on Mars, I'm going to be waiting to see if it is obviously Earth-based DNA. If so, then as excited as people will be, it won't actually be any particular sort of evidence for wide-spread life. It'd still probably be a reasonable candidate for discovery of the century, but not the millenium. (We will be able to determine if it is has the same source as Earth-based life, because Earth-based life has a lot of things that seem like they ought to be free parameters, but are highly conserved across our entire ecosystem. This includes certain basic genes and processes and their exact "spelling" in genes, the mapping of DNA letters to proteins, and probably quite a few other things. Can't disprove a common third source that way, of course.)

jbattle 8y ago
Or ... do we have Mars-based DNA?
- jerf 8y ago
  I've seen the theory tossed out there, but it's hard to do anything about it. We'd need paleontologists on Mars to really be sure (to prove life that predates Earth, as a step 1), and we're a long way away from that no matter how you slice it. But as I understand it, the time scales work; for the same reason that Mars is basically a dried-up, used up planet now while Earth is flourishing with life, Mars was theoretically possibly habitable much earlier than Earth.