BIOL 371 Lecture Notes - Lecture 8: Great Oxygenation Event, Late Heavy Bombardment, Billion Years
Document Summary
4. 6 billion years ago (4. 6 gyr) super nova explosion. Formation of the inner planets from 500 or so planetesimals. The early eath was a fiery and inhospitable for 500 million years. Surface water originated from colissions with icy comets and asteroids, and volcanic outgassing. Solid crust was forming and water condensing to oceans as early as 4. 4-4. 3 gya. Conditions compatible with life may have been established within a few hundred million years. After the (cid:862)(cid:373)oo(cid:374)(cid:863) i(cid:373)pa(cid:272)t: rock vapor atmosphere, surface temperature lingered -100 c, steamy greenhouse. Massive meteorite impacts: 500 km in size capable of vaporizing the ocean (350 c) no good for life, 200 km in size heat above 110 c. Therefore before these events, it was highly unlikely that the oceans comprised of a sta(cid:271)le lo(cid:374)g ter(cid:373) (cid:862)pri(cid:373)ordial soup(cid:863) i(cid:374) (cid:449)hi(cid:272)h the (cid:271)uildi(cid:374)g (cid:271)lo(cid:272)ks of life, a(cid:374)d life itself (cid:272)ould ha(cid:448)e developed. Evidence for cellular life in the early archaean.
