5 ms·

Proof of life on Mars 'to come this year'

26 points by prat 17y ago

thaumaturgy 17y ago
I assume that the investigating scientists familiar with the project have reasons to conclude that the bacterial fossils definitely originated from Mars, given that: > The stones are known to be from Mars because gases trapped inside them match those in rocks examined by probes on the red planet. They were blasted out of its surface by asteroid impacts and then drifted around the solar system for millions of years before falling to earth. I would tend to more conservatively conclude, "some meteorites resembling Martian rock have been found to contain fossil evidence of bacteria." i.e., it is also possible that the rock was contaminated while in space, or that it didn't even originate from Mars, but from conditions which simulated Mars. I'd love to hear definitive proof of life, or former life, on Mars.
- pjkundert 17y ago
  Isn't it unlikely that Mars would not have bacteria, given the tons of earth-sourced meteorites that have bombarded it?
  - jerf 17y ago
    In my opinion, if we discover some life on Mars, but biochemical analysis says that it is compatible with Earth life (uses DNA, same chirality on the molecules, clear analogs with Earth life in the design, probably could even find an ancestor), we have to stick with the theory that Mars did not originate life. If Mars did independently originate life, it should be clearly obvious. "Mars is able to natively host small amounts of Earth-derived life" is still interesting and still says some things about the prospect of life in the universe, but I don't think that would really add much to what we already know, the way a truly independent branch of life would. Good cases have been made that RNA and DNA may be the only suitable bases for life, which would imply that finding those wouldn't be absolute proof, but there's enough other stuff in Earth's base DNA catalog that should be different that sequencing should immediately reveal a different origin. (Not to mention the different starting conditions should result in other choices for basic functioning.) (It is not necessary that RNA/DNA be the only choices for life; it simply means that if the arguments are even partially true it tweaks the probability that truly foreign life might still be RNA/DNA based up. But above that level I'd expect significant differences; "ontogeny recapitulates phylogeny" may be false at the macro level, but billion-year-old decisions of life are still written into our DNA at deep levels. Truly independent life should have made at least some different decisions.)
    - thaumaturgy 17y ago
      > If Mars did independently originate life, it should be clearly obvious. Why?
      - jerf 17y ago
        For the reason I talked about in my third paragraph, for starters?
        thaumaturgy 17y ago
        Well, thanks for that, but I did read your entire comment and it was an honest question. Your third paragraph, for starters, includes a lot of "should" and handwaving. In what ways were the starting conditions different? Earth underwent radical changes in its environment in its early history. Did those changes -- from a methane to an oxygen-rich atmosphere for example -- result in radically different RNA or DNA sequences for the bacteria from each epoch? Why should different starting conditions result in different forms of basic DNA anyway? Wouldn't the basic problems of evolutionary viability be the same? There is indeed lots of stuff in Earth's base DNA catalog -- including some terrestrial critters that would do just fine on Mars, which would suggest that they could have independently evolved there. Tardigrades are one such popular example. Your very last sentence is, "Truly independent life should have made at least some different decisions", but there's that word again: should. So, again: why? On a completely different side note: this is part of the reason that anti-intellectualism is so rampant in America today. Those that have the combination of both ignorance and intellectual curiosity too often get met with sarcasm and indifference by people who then complain that nobody takes their opinion seriously. So thanks for that.
        jerf 17y ago
        "Did those changes -- from a methane to an oxygen-rich atmosphere for example -- result in radically different RNA or DNA sequences for the bacteria from each epoch?" It certainly left an imprint. I can't google up a concrete reference, but there are genes in our genome that come from the era when there was a lot more methane in the general environment meant to essentially put the organism in hibernation when they temporarily encounter a certain type of high-methane environment. How "radically different" it is depends critically on your definition of "radically different". It is certainly detectably different, which is more to my point. Sequencing a Martian lifeform without those markers would stand out and provide very strong evidence that they don't come from a heritage that had that in its past. (I have no idea how widespread those genes are, so I don't know how much Earth life that would eliminate as possible ancestors.) "Why should different starting conditions result in different forms of basic DNA anyway? Wouldn't the basic problems of evolutionary viability be the same?" Genes code for chemistry. Different starting chemistry implies different solutions for problems encountered early in life's existence. Not to mention there are multiple solutions to problems, and the odds of life choosing the same initial solutions are just negligible. You can see this if you play with evolutionary programming, and look at the resulting programs. You can see it in conventional genetic programming, too, if the problem has many unrelated but equally appropriate solutions. In fact, you can see it in that music link we had a couple days ago. Any given evolutionary run tends to create a population that congregates in a relatively small part of the space, regardless of how many other viable paths there are. Evolution's ability to escape local optima is greatly oversold in the popular press. "So, again: why?" Because the probability is so long against it. Why would two 100-fair-coin-flip series ever be the same? It's theoretically possible, but you'll never see it. Basically, what my point boils down to is that a Martian life form won't fit into the phylogenetic tree of life. See http://www.talkorigins.org/faqs/comdesc/phylo.html http://www.talkorigins.org/faqs/comdesc/phylo.html , which doesn't relate the tree directly to the topic at hand IIRC, but you should see how it relates with some thought. Something that does fit into the phylogenetic tree very probably came from Earth. "Those that have the combination of both ignorance and intellectual curiosity too often get met with sarcasm and indifference by people who then complain that nobody takes their opinion seriously." I call foul. You grunted a one word question to a pull quote, a "why" that I answered two paragraphs later. If I had had no answer, I would have understood. This post of yours is not unreasonable, asking for specific further elaboration, but just "why?" didn't cut it. (You prompted me to remember the phylogenetic tree page, which puts my point on much firmer footing, which I appreciate.) Also, since I can smell the "But you can't prove any of that" coming, I would say, prove for me that life will exactly evolve the same way on Mars that it would on Earth. Actually, I explicitly won't hold you to that, because we're all speculating and handwaving. Even a biochemist of fifty years practice is just speculating and handwaving. Until we start building artificial life forms and start really exploring the space of "valid life forms" neither you nor I nor anybody have the actual data in hand. (We're just barely at the threshold of artificial life and by no means have we even begun exploring the space of possible life.) However, if you go back to my original post, I actually make a judgment call on probabilities, so it's not like that's news to me that it won't be proof.
motters 17y ago
I remain skeptical about anything found on earth, since life is so pervasive here. Even if the meteorites do contain fossils it might be possible that their chemical composition just happens by mere coincidence to be similar to that of Mars. I'd be much more persuaded if a rover on the planet was to find fossils, or if a sample return mission was found to contain fossils.
Eliezer 17y ago
If anyone actually believes that, I'd like to bet with them about it.
- amichail 17y ago
  At the very least, this would result in quite a lot more spacecraft going to Mars. This could also have a rather negative effect on religion.
  - byrneseyeview 17y ago
    This could also have a rather negative effect on religion. I only ever hear non-religious people say that. Very few religious people will say "If you proved that, my faith would be shaken."
    - DanielBMarkham 17y ago
      It's a cultural myth. Western religions have dealt with "outsiders" and "aliens" for hundreds of years and have done just fine with it. New life forms, intelligent or not, will not change much of anything. In fact, for a religion to have been successful over the millenia implies a high degree of adaptability. Otherwise we wouldn't have just gotten through celebrating Saturnalia, I mean, er, Christmas.
      - amichail 17y ago
        The most recent things that have hurt religion are the web and 9/11. This will be the third. We are talking about the greatest discovery that could be made. It is one that will make billions rethink their role in the universe. It will make them wonder about evolution, whether their God guided it and if so to what degree.
        byrneseyeview 17y ago
        In the time since you made that comment, someone gave birth, and that made them rethink their role in the universe. Vague discoveries of space bacteria won't do it.
asmithmd1 17y ago
The discovery of distinct plumes of methane that peak in Martian spring and Summer are to me strong evidence that something biological is going on: http://www.nasa.gov/mission_pages/mars/news/marsmethane.html http://www.nasa.gov/mission_pages/mars/news/marsmethane.html The more seasons we see this pattern happen the less likely it is some volcanic/geological source.
herdrick 17y ago
Unlikely. The photos we have already are almost good enough to definitively say if those formations are biological, right? What are the chances that some given biologically formed nodules would be right at that size threshold? Besides, I've talked to geologists who say those rocks look perfectly non-organic to them.
wrs 17y ago
The current issue of SciAm has an article saying "nanobacteria" (as "fossilized" in Mars meteorites) are just crystal formations that look a lot like tiny bacteria. The authors demonstrated growth of "nanobacteria" in solution. Tiny online excerpt: http://www.scientificamerican.com/article.cfm?id=the-rise-and-fall-of-nanobacteria http://www.scientificamerican.com/article.cfm?id=the-rise-an...

26 points by prat 17y ago

I assume that the investigating scientists familiar with the project have reasons to conclude that the bacterial fossils definitely originated from Mars, given that: > The stones are known to be from Mars because gases trapped inside them match those in rocks examined by probes on the red planet. They were blasted out of its surface by asteroid impacts and then drifted around the solar system for millions of years before falling to earth. I would tend to more conservatively conclude, "some meteorites resembling Martian rock have been found to contain fossil evidence of bacteria." i.e., it is also possible that the rock was contaminated while in space, or that it didn't even originate from Mars, but from conditions which simulated Mars. I'd love to hear definitive proof of life, or former life, on Mars.

pjkundert 17y ago
Isn't it unlikely that Mars would not have bacteria, given the tons of earth-sourced meteorites that have bombarded it?
- jerf 17y ago
  In my opinion, if we discover some life on Mars, but biochemical analysis says that it is compatible with Earth life (uses DNA, same chirality on the molecules, clear analogs with Earth life in the design, probably could even find an ancestor), we have to stick with the theory that Mars did not originate life. If Mars did independently originate life, it should be clearly obvious. "Mars is able to natively host small amounts of Earth-derived life" is still interesting and still says some things about the prospect of life in the universe, but I don't think that would really add much to what we already know, the way a truly independent branch of life would. Good cases have been made that RNA and DNA may be the only suitable bases for life, which would imply that finding those wouldn't be absolute proof, but there's enough other stuff in Earth's base DNA catalog that should be different that sequencing should immediately reveal a different origin. (Not to mention the different starting conditions should result in other choices for basic functioning.) (It is not necessary that RNA/DNA be the only choices for life; it simply means that if the arguments are even partially true it tweaks the probability that truly foreign life might still be RNA/DNA based up. But above that level I'd expect significant differences; "ontogeny recapitulates phylogeny" may be false at the macro level, but billion-year-old decisions of life are still written into our DNA at deep levels. Truly independent life should have made at least some different decisions.)
  - thaumaturgy 17y ago
    > If Mars did independently originate life, it should be clearly obvious. Why?
    - jerf 17y ago
      For the reason I talked about in my third paragraph, for starters?
      - thaumaturgy 17y ago
        Well, thanks for that, but I did read your entire comment and it was an honest question. Your third paragraph, for starters, includes a lot of "should" and handwaving. In what ways were the starting conditions different? Earth underwent radical changes in its environment in its early history. Did those changes -- from a methane to an oxygen-rich atmosphere for example -- result in radically different RNA or DNA sequences for the bacteria from each epoch? Why should different starting conditions result in different forms of basic DNA anyway? Wouldn't the basic problems of evolutionary viability be the same? There is indeed lots of stuff in Earth's base DNA catalog -- including some terrestrial critters that would do just fine on Mars, which would suggest that they could have independently evolved there. Tardigrades are one such popular example. Your very last sentence is, "Truly independent life should have made at least some different decisions", but there's that word again: should. So, again: why? On a completely different side note: this is part of the reason that anti-intellectualism is so rampant in America today. Those that have the combination of both ignorance and intellectual curiosity too often get met with sarcasm and indifference by people who then complain that nobody takes their opinion seriously. So thanks for that.
        jerf 17y ago
        "Did those changes -- from a methane to an oxygen-rich atmosphere for example -- result in radically different RNA or DNA sequences for the bacteria from each epoch?" It certainly left an imprint. I can't google up a concrete reference, but there are genes in our genome that come from the era when there was a lot more methane in the general environment meant to essentially put the organism in hibernation when they temporarily encounter a certain type of high-methane environment. How "radically different" it is depends critically on your definition of "radically different". It is certainly detectably different, which is more to my point. Sequencing a Martian lifeform without those markers would stand out and provide very strong evidence that they don't come from a heritage that had that in its past. (I have no idea how widespread those genes are, so I don't know how much Earth life that would eliminate as possible ancestors.) "Why should different starting conditions result in different forms of basic DNA anyway? Wouldn't the basic problems of evolutionary viability be the same?" Genes code for chemistry. Different starting chemistry implies different solutions for problems encountered early in life's existence. Not to mention there are multiple solutions to problems, and the odds of life choosing the same initial solutions are just negligible. You can see this if you play with evolutionary programming, and look at the resulting programs. You can see it in conventional genetic programming, too, if the problem has many unrelated but equally appropriate solutions. In fact, you can see it in that music link we had a couple days ago. Any given evolutionary run tends to create a population that congregates in a relatively small part of the space, regardless of how many other viable paths there are. Evolution's ability to escape local optima is greatly oversold in the popular press. "So, again: why?" Because the probability is so long against it. Why would two 100-fair-coin-flip series ever be the same? It's theoretically possible, but you'll never see it. Basically, what my point boils down to is that a Martian life form won't fit into the phylogenetic tree of life. See http://www.talkorigins.org/faqs/comdesc/phylo.html http://www.talkorigins.org/faqs/comdesc/phylo.html , which doesn't relate the tree directly to the topic at hand IIRC, but you should see how it relates with some thought. Something that does fit into the phylogenetic tree very probably came from Earth. "Those that have the combination of both ignorance and intellectual curiosity too often get met with sarcasm and indifference by people who then complain that nobody takes their opinion seriously." I call foul. You grunted a one word question to a pull quote, a "why" that I answered two paragraphs later. If I had had no answer, I would have understood. This post of yours is not unreasonable, asking for specific further elaboration, but just "why?" didn't cut it. (You prompted me to remember the phylogenetic tree page, which puts my point on much firmer footing, which I appreciate.) Also, since I can smell the "But you can't prove any of that" coming, I would say, prove for me that life will exactly evolve the same way on Mars that it would on Earth. Actually, I explicitly won't hold you to that, because we're all speculating and handwaving. Even a biochemist of fifty years practice is just speculating and handwaving. Until we start building artificial life forms and start really exploring the space of "valid life forms" neither you nor I nor anybody have the actual data in hand. (We're just barely at the threshold of artificial life and by no means have we even begun exploring the space of possible life.) However, if you go back to my original post, I actually make a judgment call on probabilities, so it's not like that's news to me that it won't be proof.

motters 17y ago

I remain skeptical about anything found on earth, since life is so pervasive here. Even if the meteorites do contain fossils it might be possible that their chemical composition just happens by mere coincidence to be similar to that of Mars. I'd be much more persuaded if a rover on the planet was to find fossils, or if a sample return mission was found to contain fossils.

Eliezer 17y ago

If anyone actually believes that, I'd like to bet with them about it.

amichail 17y ago
At the very least, this would result in quite a lot more spacecraft going to Mars. This could also have a rather negative effect on religion.
- byrneseyeview 17y ago
  This could also have a rather negative effect on religion. I only ever hear non-religious people say that. Very few religious people will say "If you proved that, my faith would be shaken."
  - DanielBMarkham 17y ago
    It's a cultural myth. Western religions have dealt with "outsiders" and "aliens" for hundreds of years and have done just fine with it. New life forms, intelligent or not, will not change much of anything. In fact, for a religion to have been successful over the millenia implies a high degree of adaptability. Otherwise we wouldn't have just gotten through celebrating Saturnalia, I mean, er, Christmas.
    - amichail 17y ago
      The most recent things that have hurt religion are the web and 9/11. This will be the third. We are talking about the greatest discovery that could be made. It is one that will make billions rethink their role in the universe. It will make them wonder about evolution, whether their God guided it and if so to what degree.
      - byrneseyeview 17y ago
        In the time since you made that comment, someone gave birth, and that made them rethink their role in the universe. Vague discoveries of space bacteria won't do it.

asmithmd1 17y ago

The discovery of distinct plumes of methane that peak in Martian spring and Summer are to me strong evidence that something biological is going on: http://www.nasa.gov/mission_pages/mars/news/marsmethane.html http://www.nasa.gov/mission_pages/mars/news/marsmethane.html The more seasons we see this pattern happen the less likely it is some volcanic/geological source.

herdrick 17y ago

Unlikely. The photos we have already are almost good enough to definitively say if those formations are biological, right? What are the chances that some given biologically formed nodules would be right at that size threshold? Besides, I've talked to geologists who say those rocks look perfectly non-organic to them.

wrs 17y ago

The current issue of SciAm has an article saying "nanobacteria" (as "fossilized" in Mars meteorites) are just crystal formations that look a lot like tiny bacteria. The authors demonstrated growth of "nanobacteria" in solution. Tiny online excerpt: http://www.scientificamerican.com/article.cfm?id=the-rise-and-fall-of-nanobacteria http://www.scientificamerican.com/article.cfm?id=the-rise-an...