Talk:Geologic timeline
[edit] Brief note on the Hadean
The Hadean is only informal, since the ICS doesn't officially recognize it as a valid geologic interval. Although, something interesting was going on during the "Hadean", given that abiogenesis must have occurred during it, never mind the giant asteroids that repeatedly hit the Earth 4.2-3.8 Ga, in which case if life had originated prior to the Late Heavy Bombardment then it would have been wiped out due to repeated asteroid collisions in the Neohadean-Eoarchean eras. It was also the time when the Earth's first atmosphere and oceans originated. Another hypothesis was that life was seeded from space during this period, which I find unlikely because of the lack of evidence in favor of panspermia. Another variant of this hypothesis is directed panspermia, an even unlikelier event in which extraterrestrials "seeded" life on Earth, which brings the need for even more evidence for this claim.--Palaeonictis (talk) 04:15, 28 November 2014 (UTC)