Radioactivity as a significant energy source in prebiotic synthesis

Radioactivity in the continental crust (due mainly to the isotopes U-238, U -235, Th-232 and K-40), as a energy source for chemical evolution in the ea rly Archean (between 3.5 and approximate to4 Ga bp), is reviewed. The most important radioactive source in the continental crust is due to the product ion and accumulation of radioactive gases within the crust voids (porosity) . The study of such mechanism has allowed us to reach a deeper understandin g about the nature of the radioactive source and to describe its behavior, particularly with regard to prebiotic chemical evolution. An effective tota l energy of 3 x 10(18) Ja(-1) has been obtained for a depth of 1 km, 4 Ga a go. If a depth of 30 km is taken, the obtained value is almost equal to the UV solar energy radiation (lambda <150 nm). Within the voids the radioacti ve source of the continental crust played a relevant role in prebiotic synt hesis. In uranium deposits of the same age, the role of radiactivity must h ave been even more relevant in favoring chemical evolution.