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I think "ancient disasters" must be referring to the Late Heavy Bombardment, which is the only putative disaster I know of that could have sterilized the surfac
by andrewflnr 1y ago
I think "ancient disasters" must be referring to the Late Heavy Bombardment, which is the only putative disaster I know of that could have sterilized the surface. Though it was supposed to fully re-liquefy the crust, so even underground life surviving would be dicey. https://en.wikipedia.org/wiki/Late_Heavy_Bombardment https://en.wikipedia.org/wiki/Late_Heavy_Bombardment
- maxbond 1y agoIt's possible life existed in the Hadean epoch before the Late Heavy Bombardment, but for the most part there are no rocks from the Hadean epoch so it's difficult to say whether there was life. Those rocks were swept into the mantle. There's a tiny bit of evidence for it from isotopic ratios within Zircon crystals which have survived that long (they are robust enough to survive the mantle and resurface), but it isn't definitive. Much like a sibling comment notes that we haven't been able to drill deep enough to find a depth without life, we haven't found rocks old enough to prove the nonexistence of life at any point in time, but if those rocks do exist they are no longer on Earth (eg they were ejected during an impact).