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> with that logic we most probably already (re?)introduced life on Mars. It's not unlikely that all the solar system's planets have been contaminating each oth

by Udo 3y ago

> with that logic we most probably already (re?)introduced life on Mars. It's not unlikely that all the solar system's planets have been contaminating each other for billions of years. All it takes is a big asteroid impact and some luck, and then some bacteria hitches a ride. The tough part is of course thriving after the organism arrives. Given Mars' current climate and surface perchlorate levels, I'm not convinced it's likely that something from here takes root over there without some help.

marcus_holmes 3y ago
I'm always intrigued by this. How big a rock would need to impact to throw a chunk all the way up Earth's gravity well? And does escape velocity create the same kind of atmospheric friction problems that re-entry does (so it'll need to be a big chunk or the bacterium needs to resist extreme heat)? The whole chain of "really big rock -> chunk of Earth leaving the gravity well -> getting into some kind of stable orbit where it can be pulled into Mars -> surviving re-entry on Mars" doesn't seem like it would happen enough times to create the kind of odds of success that would be needed for a bacterium to successfully colonise Mars.
- h2odragon 3y ago
  > does escape velocity create the same kind of atmospheric friction problems Yes; but those temperatures may not penetrate deep into the body of the rock; so there still might be biology surviving.
pfdietz 3y ago
It's also possible that life originated on Mars (back when it was young and much more conducive to life) and was then introduced to Earth. Or, that life bounced back and forth between the planets as each was affected by large sterilizing impacts in the early solar system, the other acting as a refugee from which the sterilized sister planet could be reinoculated.
chmod775 3y ago
Kurzgesagt recently had an interesting video on how life might have been everywhere when the universe was still young and essentially every inch of it had temperatures to support it. The bit that sold me on the idea was when they noted that the complexity of life seems to double every 250m years. But apparently if you roll with that assumption and extrapolate all the way back to the simplest conceivable organism, you end up at time when earth didn't exist and the universe was young.

by Udo 3y ago

marcus_holmes 3y ago

I'm always intrigued by this. How big a rock would need to impact to throw a chunk all the way up Earth's gravity well? And does escape velocity create the same kind of atmospheric friction problems that re-entry does (so it'll need to be a big chunk or the bacterium needs to resist extreme heat)? The whole chain of "really big rock -> chunk of Earth leaving the gravity well -> getting into some kind of stable orbit where it can be pulled into Mars -> surviving re-entry on Mars" doesn't seem like it would happen enough times to create the kind of odds of success that would be needed for a bacterium to successfully colonise Mars.

h2odragon 3y ago
> does escape velocity create the same kind of atmospheric friction problems Yes; but those temperatures may not penetrate deep into the body of the rock; so there still might be biology surviving.

pfdietz 3y ago

It's also possible that life originated on Mars (back when it was young and much more conducive to life) and was then introduced to Earth. Or, that life bounced back and forth between the planets as each was affected by large sterilizing impacts in the early solar system, the other acting as a refugee from which the sterilized sister planet could be reinoculated.

chmod775 3y ago

Kurzgesagt recently had an interesting video on how life might have been everywhere when the universe was still young and essentially every inch of it had temperatures to support it. The bit that sold me on the idea was when they noted that the complexity of life seems to double every 250m years. But apparently if you roll with that assumption and extrapolate all the way back to the simplest conceivable organism, you end up at time when earth didn't exist and the universe was young.