8 ms·

But then how did life get on mars?

by NegativeLatency 2y ago

alex_young 2y ago
Blew in from Europa
deleted 2y ago
[deleted]
bena 2y ago
Exactly, panspermia isn't an answer, it's kicking the can down the road. The only thing panspermia can tell us is that it's ok if we can't find evidence for the genesis of life on Earth.
- wddkcs 2y ago
  All science is the process of kicking the can further down the road.
  - b800h 2y ago
    Excellent comment. Kalām cosmological argument.
- adastra22 2y ago
  Which is an important advance because genesis of life on Earth is getting harder and harder to answer as we gather more evidence. Pushing it to another environment (and longer time frame) does in fact solve a number of problems.
  - 48864w6ui 2y ago
    What evidence? Do we no longer figure ~4by bp?
  - bena 2y ago
    I'd say it just ignores any problems. However, haven't we roughly recreated the process in a lab in the last couple of decades? And we may never have the answer because we simply can't know because no one was there because nothing was there. But there's a plausible enough explanation that we don't need to invoke the extraterrestrial and all of its problems. And I think that's part of the appeal of panspermia, it makes life extraterrestrial. And if it is extraterrestrial in origin, then it could have happened elsewhere. Whereas if the genesis of life is contained to Earth, then the chances go down that it happened somewhere else.
    - adastra22 2y ago
      No there hasn’t been any (successful) abiogenesis experiments yet.
Insanity 2y ago
I get your point, but the idea that life originates on Asteroids and populates planets on impact is, imo, likely. It does shift the question to “how did it start there” :)
- fullstackchris 2y ago
  do asteroids even have all the elements / compounds necessary to support the building blocks of life?
  - adastra22 2y ago
    Yes. In fact some have surprisingly complex organic chemistry—amino acids and everything.
  - marcosdumay 2y ago
    Apparently, yes. But they don't have nearly as many opportunities to react as in a hot planet with an atmosphere. So pushing that life started there instead of only recognizing it's a very unlikely (but still possible) possibility isn't sustained by evidence.
  - adrian_b 2y ago
    They have the chemical elements, but they do not have a source of energy that could create life. For the appearance of life, a planet with a hot interior and volcanism is necessary, so that minerals that are stable only at high temperatures in the interior are ejected to the surface, where after cooling down they are no longer in chemical equilibrium, providing the energy necessary to drive the synthesis of organic macromolecules (by producing through chemical reactions with water reduced compounds like dihydrogen and carbon monoxide, which can reduce the abundant carbon dioxide and dinitrogen to eventually generate amino-acids). The solar energy cannot play any role in the appearance of life, because harvesting it requires systems that are much more complex than those that appear naturally in the inorganic minerals and fluids. While the Earth had certainly all the preconditions for the appearance of life right here, it is likely that Mars also had them in the beginning. What another poster has said is plausible, i.e. the only reason for supposing that life could have been brought on Earth from another place is that life has appeared rather quickly on Earth, even if this is an event with a much lower probability than all the other events that have occurred after that during the evolution towards more complex forms of life, which have required billions of years to happen. If life has been transferred to Earth from elsewhere, Mars is the only plausible source, because it had the conditions necessary to generate life long enough before Earth and because fragments from Mars have been frequently transported to Earth, where they fall as meteorites, after being ejected from Mars by impacts that happened there, which is easier than from other planets due to the lower gravity. Despite the fact that it is not impossible, I doubt that life has been brought from Mars, but it is indeed puzzling that life seems to have appeared very quickly on Earth. There are also facts that are hard to explain by the hypothesis of transfer from Mars. If that happened, than the forms of life that have been transferred must have consisted of at least one kind of autotrophic "bacteria" and at least several distinct kinds of viruses, to explain all the existing living beings as their descendants. There is considerable evidence for the fact that the current genetic code of the nucleic acids is the product of a long evolution process. In the beginning there must have been a simpler code where many more combinations were equivalent and which encoded no more than 10 amino-acids, perhaps only 6 or even only 4 in its original variant. So very ancient "bacteria" may have superficially looked like modern bacteria but they must have had a quite different metabolism. In the hypothesis where life has moved between planets, there would be an open problem of when had the transfer happened during this early evolution of the genetic system. On Earth there has remained no survivor with a much simpler genetic code (though there are a few examples of only slightly simpler genetic codes than the canonic variant). Perhaps the earlier living beings were completely uncompetitive with the modern ones, so they have been eaten or they have starved to death. In the case of a transfer from Mars, it would also exist the possibility that only living beings with a complex genetic code had survived through a transfer and the others had remained on Mars.
adastra22 2y ago
Mars had 3/4 billion more years to develop, compared with the Earth. Mars formed first, and cooled first due to its smaller size. One of the outstanding problems in astrobiology I mention is that the Earth was inhospitable until 3.8Gya, and the oldest fossils of presumably DNA based life (since it matches existing life we can study) was 3.7Gya. Mars was hospitable ~4.5Gya. So either life emerged IMMEDIATELY on Earth and did a complexity speed run before slowing down and remaining stagnant for the next billion years or so, or it emerged on Mars first and Earth was seeded once it was cool enough.
- jerpint 2y ago
  How does earth get seeded?
  - adastra22 2y ago
    Look up ALH-84001. The debate about whether the structures inside this Martian meteorite are fossils is too long for a HN post. But in analyzing the rock it was shown that the during the entire trip from when it was blasted out of Mars to when it fell in Antarctica would have been survivable for rock boring microbes. Not just theoretically, but hard evidence. There are structures that would have been destroyed if the rock was heated enough to sterilize, but they survived the trip. Hundreds of tons of rock like this from Mars land every year.
    - Qem 2y ago
      Related talk: https://m.youtube.com/watch?v=ekJQUS7WP78&t=57s&pp=ygUPS2lyc2NodmluayB0YWxr https://m.youtube.com/watch?v=ekJQUS7WP78&t=57s&pp=ygUPS2lyc...
    - iamthirsty 2y ago
      > Hundreds of tons of rock like this from Mars land every year. 277 total Martian meteorites — with the largest weighing 14.5 kg — is not hundreds of tons yearly.
      - 2y ago
pfdietz 2y ago
I remember seeing somewhere a graph where someone plotted the "complexity" of life vs. time, I think on a log plot, and found a straight line. The line goes to (log) 0 around 5 billion years before the formation of the solar system. The inference from this admittedly dubious exercise was that life originated somewhere before our Solar system, spread here, and continued to evolve here. I think it was maybe from this source? https://www.sciencedirect.com/science/article/abs/pii/B9780128119402000113 https://www.sciencedirect.com/science/article/abs/pii/B97801...
- AnimalMuppet 2y ago
  What definition of "complexity" lets it be linear across the Cambrian Explosion?
  - pfdietz 2y ago
    Size of genome, I think. Not clear how they estimate that for deep time.
caseyy 2y ago
Maybe Earth? Who knows? Lots of good sci-fi has been written about it. I recommend J.P. Hogan’s “Inherit the Stars”, which starts with evidence of human spaceflight predating known history and goes on interesting directions.
jimnotgym 2y ago
I heard somewhere that life started on Mars, but it was all male. Can't seem to find the reference.

But then how did life get on mars?

alex_young 2y ago

Blew in from Europa

deleted 2y ago

[deleted]

bena 2y ago

Exactly, panspermia isn't an answer, it's kicking the can down the road. The only thing panspermia can tell us is that it's ok if we can't find evidence for the genesis of life on Earth.

wddkcs 2y ago
All science is the process of kicking the can further down the road.
- b800h 2y ago
  Excellent comment. Kalām cosmological argument.
adastra22 2y ago
Which is an important advance because genesis of life on Earth is getting harder and harder to answer as we gather more evidence. Pushing it to another environment (and longer time frame) does in fact solve a number of problems.
- 48864w6ui 2y ago
  What evidence? Do we no longer figure ~4by bp?
- bena 2y ago
  I'd say it just ignores any problems. However, haven't we roughly recreated the process in a lab in the last couple of decades? And we may never have the answer because we simply can't know because no one was there because nothing was there. But there's a plausible enough explanation that we don't need to invoke the extraterrestrial and all of its problems. And I think that's part of the appeal of panspermia, it makes life extraterrestrial. And if it is extraterrestrial in origin, then it could have happened elsewhere. Whereas if the genesis of life is contained to Earth, then the chances go down that it happened somewhere else.
  - adastra22 2y ago
    No there hasn’t been any (successful) abiogenesis experiments yet.

Insanity 2y ago

I get your point, but the idea that life originates on Asteroids and populates planets on impact is, imo, likely. It does shift the question to “how did it start there” :)

fullstackchris 2y ago
do asteroids even have all the elements / compounds necessary to support the building blocks of life?
- adastra22 2y ago
  Yes. In fact some have surprisingly complex organic chemistry—amino acids and everything.
- marcosdumay 2y ago
  Apparently, yes. But they don't have nearly as many opportunities to react as in a hot planet with an atmosphere. So pushing that life started there instead of only recognizing it's a very unlikely (but still possible) possibility isn't sustained by evidence.
- adrian_b 2y ago
  They have the chemical elements, but they do not have a source of energy that could create life. For the appearance of life, a planet with a hot interior and volcanism is necessary, so that minerals that are stable only at high temperatures in the interior are ejected to the surface, where after cooling down they are no longer in chemical equilibrium, providing the energy necessary to drive the synthesis of organic macromolecules (by producing through chemical reactions with water reduced compounds like dihydrogen and carbon monoxide, which can reduce the abundant carbon dioxide and dinitrogen to eventually generate amino-acids). The solar energy cannot play any role in the appearance of life, because harvesting it requires systems that are much more complex than those that appear naturally in the inorganic minerals and fluids. While the Earth had certainly all the preconditions for the appearance of life right here, it is likely that Mars also had them in the beginning. What another poster has said is plausible, i.e. the only reason for supposing that life could have been brought on Earth from another place is that life has appeared rather quickly on Earth, even if this is an event with a much lower probability than all the other events that have occurred after that during the evolution towards more complex forms of life, which have required billions of years to happen. If life has been transferred to Earth from elsewhere, Mars is the only plausible source, because it had the conditions necessary to generate life long enough before Earth and because fragments from Mars have been frequently transported to Earth, where they fall as meteorites, after being ejected from Mars by impacts that happened there, which is easier than from other planets due to the lower gravity. Despite the fact that it is not impossible, I doubt that life has been brought from Mars, but it is indeed puzzling that life seems to have appeared very quickly on Earth. There are also facts that are hard to explain by the hypothesis of transfer from Mars. If that happened, than the forms of life that have been transferred must have consisted of at least one kind of autotrophic "bacteria" and at least several distinct kinds of viruses, to explain all the existing living beings as their descendants. There is considerable evidence for the fact that the current genetic code of the nucleic acids is the product of a long evolution process. In the beginning there must have been a simpler code where many more combinations were equivalent and which encoded no more than 10 amino-acids, perhaps only 6 or even only 4 in its original variant. So very ancient "bacteria" may have superficially looked like modern bacteria but they must have had a quite different metabolism. In the hypothesis where life has moved between planets, there would be an open problem of when had the transfer happened during this early evolution of the genetic system. On Earth there has remained no survivor with a much simpler genetic code (though there are a few examples of only slightly simpler genetic codes than the canonic variant). Perhaps the earlier living beings were completely uncompetitive with the modern ones, so they have been eaten or they have starved to death. In the case of a transfer from Mars, it would also exist the possibility that only living beings with a complex genetic code had survived through a transfer and the others had remained on Mars.

adastra22 2y ago

Mars had 3/4 billion more years to develop, compared with the Earth. Mars formed first, and cooled first due to its smaller size. One of the outstanding problems in astrobiology I mention is that the Earth was inhospitable until 3.8Gya, and the oldest fossils of presumably DNA based life (since it matches existing life we can study) was 3.7Gya. Mars was hospitable ~4.5Gya. So either life emerged IMMEDIATELY on Earth and did a complexity speed run before slowing down and remaining stagnant for the next billion years or so, or it emerged on Mars first and Earth was seeded once it was cool enough.

jerpint 2y ago
How does earth get seeded?
- adastra22 2y ago
  Look up ALH-84001. The debate about whether the structures inside this Martian meteorite are fossils is too long for a HN post. But in analyzing the rock it was shown that the during the entire trip from when it was blasted out of Mars to when it fell in Antarctica would have been survivable for rock boring microbes. Not just theoretically, but hard evidence. There are structures that would have been destroyed if the rock was heated enough to sterilize, but they survived the trip. Hundreds of tons of rock like this from Mars land every year.
  - Qem 2y ago
    Related talk: https://m.youtube.com/watch?v=ekJQUS7WP78&t=57s&pp=ygUPS2lyc2NodmluayB0YWxr https://m.youtube.com/watch?v=ekJQUS7WP78&t=57s&pp=ygUPS2lyc...
  - iamthirsty 2y ago
    > Hundreds of tons of rock like this from Mars land every year. 277 total Martian meteorites — with the largest weighing 14.5 kg — is not hundreds of tons yearly.
    - 2y ago

pfdietz 2y ago

I remember seeing somewhere a graph where someone plotted the "complexity" of life vs. time, I think on a log plot, and found a straight line. The line goes to (log) 0 around 5 billion years before the formation of the solar system. The inference from this admittedly dubious exercise was that life originated somewhere before our Solar system, spread here, and continued to evolve here. I think it was maybe from this source? https://www.sciencedirect.com/science/article/abs/pii/B9780128119402000113 https://www.sciencedirect.com/science/article/abs/pii/B97801...

AnimalMuppet 2y ago
What definition of "complexity" lets it be linear across the Cambrian Explosion?
- pfdietz 2y ago
  Size of genome, I think. Not clear how they estimate that for deep time.

caseyy 2y ago

Maybe Earth? Who knows? Lots of good sci-fi has been written about it. I recommend J.P. Hogan’s “Inherit the Stars”, which starts with evidence of human spaceflight predating known history and goes on interesting directions.

jimnotgym 2y ago

I heard somewhere that life started on Mars, but it was all male. Can't seem to find the reference.