Question 2: relation of panspermia-hypothesis to astrobiology.
In the answer to major questions of astrobiology and chirality, the panspermia-hypothesis is often discussed as the only proposal of transportation of life to the Earth. On the basis of the known presence of ionizing radiation in the space, assumed on the level calculated by Clark (Orig Life Evol Biosph 31:185-197, 2001), the hypothesis is rejected as the explanation of origins of life on Earth. In fact, comparatively low doses of radiation sterilize irreversibly all biological material. Sufficiently long sojourn in space of objects containing prebiotic chemical blocks also does not contribute to the origins of life on Earth, because of elimination of homochirality, if any, and of radiation induced reactions of dehydrogenation, decarboxylation and deamination of chemical compounds closing with complete decomposition of organics, leaving elementary nano-carbon and/or minerals like calcium carbonate.
Zagorski
Zbigniew Pawel
ZP
Department of Radiation Chemistry, Institute of Nuclear Chemistry and Technology, Warsaw, Poland. zagorski@ichtj.waw.pl
D018559:Exobiology; D008962:Models, Theoretical; D008968:Molecular Conformation; D000069497:Origin of Life; D011839:Radiation, Ionizing