Radioactivity as a Significant Energy Source in Prebiotic Synthesis

Radioactivity in the continental crust (due mainly to the isotopes ²³⁸U,²³⁵U, ²³²Th and ⁴⁰K), as a energysource for chemical evolution in the early Archean (between 3.5 and 4 Ga bp), is reviewed.The most important radioactive sourcein the continental crust is due to theproduction and accumulation of radioactivegases within the crust voids (porosity). Thestudy of such mechanism has allowed us toreach a deeper understanding about the nature of the radioactive source and to describe itsbehavior, particularly with regard to prebiotic chemical evolution. An effectivetotal energy of 3 × 10^18Ja-1 hasbeen obtained for a depth of 1 km, 4 Ga ago. If a depth of 30 km is taken, the obtained valueis almost equal to the UV solar energyradiation (<150 nm). Within thevoids the radioactive source of thecontinental crust played a relevant role inprebiotic synthesis. In uraniumdeposits of the same age, the role ofradiactivity must have been even more relevantin favoring chemical evolution.