SparseGhostC2C t1_j1zt1bq wrote on December 28, 2022 at 5:01 PM

So how do we go from whatever "original" ice ball asteroid impacted earth however many bya to having enough water to cover the majority of the earth's surface?

Like surely that one asteroid, or the small number of them that have made it to Earth's surface during its lifetime, were not sufficient to generate all the water we have here. I'm honestly curious where it came from or how we got so much, was it generated here by some kind of chemistry or was it all deposited from space?

FluffyGarbage23 t1_j20hewe wrote on December 28, 2022 at 7:41 PM

Im curious as well. It wouldve been millions, or billions, or trillions of asteroids large enough to not break up, but large enough to "survive" an impact with Earth for long enough to not get instantly evaporated by proto-Earth lavas and what not.

Its not exactly like theyre balloons filled up with water being thrown at Earth, theyre mostly just rock, minerals and metals.

Unless we got lucky and got a bunch of massive ice-asteroids.

SparseGhostC2C t1_j20i498 wrote on December 28, 2022 at 7:45 PM

Another reply to me had suggested much of it may have come along during the Theia impact which lead to the creation of the moon, since the object that would have collided with earth would've been much larger than your average asteroid or meteor. It sounds totally plausible but I'm still very curious to find more info.

citro-naut t1_j227b6e wrote on December 29, 2022 at 2:54 AM

Keep in mind that once earth became sufficiently large, even volatiles that were vaporized would still be retained. Just think about how we can boil water today and it’s not like the water vapor disappears to space.

citro-naut t1_j2273gz wrote on December 29, 2022 at 2:52 AM

Earth formed by the accretion of countless small bodies ranging in size from pebbles to Nara-sized bodies. Some fraction of these planetesimals formed in the region where earth exists today (inner solar system) and likely had enough water to meet earths current inventory. Another probably smaller fraction of bodies from the outer solar system (like Ryugu and the other progenitors of CI chondrites) were also accreted and surely delivered some fraction to water. But to answer your question, earth was accreting water-bearing asteroids and planetesimals all throughout its accretionary history. It wasn’t a one-off event or even just a few random chance impacts.

Penguinkeith t1_j207k4z wrote on December 28, 2022 at 6:36 PM

Theia impact probably brought most of the water if it formed in the outer solar system