Sprecher
Beschreibung
How life originated is how geochemistry became biochemistry. Consequently, knowing the environmental geochemistry prior to the origin of life is crucial. Here, I discuss the expected chemical composition of the early atmosphere and surface waters. In the Hadean, calculations show that chemically reducing atmospheres are inevitable consequences of large impacts and would have lasted millions of years, producing copious nitriles that rained out to the surface, serving as feedstocks for nucleobase synthesis. Also on the early Earth, evaporative soda lakes (i.e., rich in sodium carbonate) are likely inevitable because such lakes arise when water pools in closed basins in basaltic rocks and the aquatic chemistry evolves. The chemistry of such lakes encourages the sequestration and concentration of key species needed for prebiotic synthesis, such as cyanide and phosphate. Such lakes can also promote polymerization of prebiotic molecules during the dry phase of wet-dry cycles. Indeed, one modern, evaporative soda lake, Last Chance Lake in Canada, can be considered a geochemical origin-of-life analog. This closed-basin lake sits on top of flood basalts, has suppressed nitrogen fixation (which inhibits the usual drastic biological modification of modern water chemistries), and has the highest phosphate levels in the world that reach almost ~40 mM. I postulate that similar locales on the early Earth would have favored prebiotic synthesis.
