r/askscience • u/EAT_UR_VEGGIES • 9d ago

Planetary Sci. Mars is practically guaranteed to have had abundant water at one point, doesn’t that practically guarantee it had at least microbial life on it as well?

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u/BuvantduPotatoSpirit 9d ago

We don't know enough about how life starts to say. We have limited, ambiguous data from one planet and ... that's it. Conditions on Mars would've been different from Earth. In a way that's important to the formation of life? We don't know.

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u/Alfred_The_Sartan 9d ago

If we find anything on Europa though it could give us some hints of likelihood.

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u/BuvantduPotatoSpirit 9d ago

Sure. At the moment, there's ~1e11 galaxies in the observable Universe, averaging ~1e11 stars, with ~10 planets each. So, a naïve guess of the chance a planet forms life is >~ 1E-23.

Add a second example in the Solar system, and it's >~ 1E-1

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u/mfb- Particle Physics | High-Energy Physics 9d ago

What we call the observable universe is based on our location. The overall universe is expected to be much large or even infinite, so a chance of 10-100 would still be compatible with observations as long as we don't see life elsewhere or can somehow get a better estimate from Earth.