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Yes, but it has been shown that Earth and Mars have been impacted by comets or meteors, and ejected matter into space which then hit the other planet. Life, or

Yes, but it has been shown that Earth and Mars have been impacted by comets or meteors, and ejected matter into space which then hit the other planet. Life, or at least molecules that are precursors to life, could easily have hopped a ride on these. If it happened later, say after bacteria had evolved, then bacterial spores could have been transported as well. Those things are really hard to destroy. As for a planet that is Earth-like (or Mars-like when Mars was similar to Earth), I think it is a 98% chance or higher. I'd be willing to bet that if life was wiped out on Earth, it would occur again in a billion years or so. It just seems like matter in general has the tendency to organize and behave in a way that favors life. It does things randomly, but once something happens that can kind of reproduce, it stays around. A bunch of these accumulate until it starts to resemble a cell. Many chemical reactions in life would happen on their own in enough time. We use enzymes to make this happen faster. Early life takes a long time to evolve up because it doesn't have these enzymes, so it has to wait for the reaction to just happen. Consciousness, or what we consider consciousness, is perhaps another story.

jey 19y ago
"As for a planet that is Earth-like (or Mars-like when Mars was similar to Earth), I think it is a 98% chance or higher." I suppose this is where we disagree. I put it at well under 1%, even if we were to assume that the panspermia hypothesis is true. On the other hand, assuming panspermia, there's enough of a chance for life to be on Mars given the fact that its neighbor has life. Finding life on Mars could also lend support to the panspermia hypothesis.
- Retric 19y ago
  The earth is around 4.5 billion years old. Life showed up within the first 1/2 billion years right around the time it cooled off enough for life to be possible. But let's say it's 50 / 50 every 500 million years (I think it's a lot higher than that.) well that's 99.8% after 4.5 billion years. Note: If that seems high it's about the same as 1 chance in 1000 per million years for any form of life to show up.
  - jey 19y ago
    Jey draws a ball from an urn, inspects it, and sees that it is a red ball. I now proclaim that all balls in the urn are red.
    - Retric 19y ago
      I agree that extracting information from a sample size of one is a bad idea but so is ignoring all evidence even if the sample size is one. Anyway, life need not be a complex process: http://www.livescience.com/animals/060609_life_origin.html http://www.livescience.com/animals/060609_life_origin.html It might seem odd for a random process to end up with a life form but there are a lot of possible life forms that could work. AKA picking a single winning lottery ticket is hard but winning the lottery is not that hard if you could buy a million tickets that never expire.

jey 19y ago

"As for a planet that is Earth-like (or Mars-like when Mars was similar to Earth), I think it is a 98% chance or higher." I suppose this is where we disagree. I put it at well under 1%, even if we were to assume that the panspermia hypothesis is true. On the other hand, assuming panspermia, there's enough of a chance for life to be on Mars given the fact that its neighbor has life. Finding life on Mars could also lend support to the panspermia hypothesis.

Retric 19y ago
The earth is around 4.5 billion years old. Life showed up within the first 1/2 billion years right around the time it cooled off enough for life to be possible. But let's say it's 50 / 50 every 500 million years (I think it's a lot higher than that.) well that's 99.8% after 4.5 billion years. Note: If that seems high it's about the same as 1 chance in 1000 per million years for any form of life to show up.
- jey 19y ago
  Jey draws a ball from an urn, inspects it, and sees that it is a red ball. I now proclaim that all balls in the urn are red.
  - Retric 19y ago
    I agree that extracting information from a sample size of one is a bad idea but so is ignoring all evidence even if the sample size is one. Anyway, life need not be a complex process: http://www.livescience.com/animals/060609_life_origin.html http://www.livescience.com/animals/060609_life_origin.html It might seem odd for a random process to end up with a life form but there are a lot of possible life forms that could work. AKA picking a single winning lottery ticket is hard but winning the lottery is not that hard if you could buy a million tickets that never expire.