PHYS 1000 Lecture Notes - Lecture 18: Meteoroid, Lightning, Extremophile
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If (cid:449)e a(cid:396)e goi(cid:374)g to look fo(cid:396) life else(cid:449)he(cid:396)e i(cid:374) the u(cid:374)i(cid:448)e(cid:396)se, (cid:449)e (cid:374)eed to defi(cid:374)e (cid:449)hat (cid:449)e (cid:373)ea(cid:374) (cid:271)(cid:455) (cid:862)life(cid:863). It turns out not to be so easy, particularly if we want to allow for types of life that do not appear on earth! The image below shows the 7 phases of cosmic evolution. We have already discussed particulate, galactic, stellar and planetary, and will continue with chemical evolution. We ha(cid:448)e (cid:448)e(cid:396)(cid:455) little i(cid:374)fo(cid:396)(cid:373)atio(cid:374) a(cid:271)out the fi(cid:396)st (cid:271)illio(cid:374) (cid:455)ea(cid:396)s of ea(cid:396)th"s e(cid:454)iste(cid:374)(cid:272)e; ea(cid:396)th (cid:449)as si(cid:373)ply too active at that time. It is believed that there many volcanoes, and an atmosphere of hydrogen, nitrogen, and carbon compounds. As earth cooled, methane, ammonia, carbon dioxide, and water formed. Earth was subject to volcanoes, lightning radioactivity, uv radiation, and meteoroid impacts. Over a billion years or so, amino acids and nucleotide bases, which form the basis of nda, formed. The process by which this happens has been recreated in the laboratory.