Biomolecules comets

Recent work suggests that there may have been a period in Europa s history when an extreme greenhouse effect led to temperatures which would have sufficed for reactions necessary for chemical evolution. According to this (unproven) hypothesis, building blocks for biomolecules or even primitive life forms could have existed. The authors assume that there is a high probability that bioelements could have been delivered by comets (Chyba and Phillips, 2002). 

More than 45 years ago, the chemist John Oro from the University of Houston, Texas, suggested that biomolecules or their precursors could have been formed in space and brought to our Earth by comets (Or6, 1961). Delsemme made similar suggestions at the ISSOL Conference in Mainz in 1983 (Delsemme, 1984). 

Until a few years ago, it was considered impossible that biomolecules or their precursors could have survived the huge temperatures which would have been generated when comets hit the Earth. Today it seems possible that about 0.1% of such substances could have remained unchanged. A comet with a diameter of around 3 km may contain around 1027 dust particles. If 0.1% were to reach Earth unchanged, there would still be 1024 intact particles around 1 mm in size. 

This demonstrates that those amino acids present in the Murchison meteorite, which also play the role of protein monomers, are indeed of extraterrestrial origin. In addition, chemical analysis has demonstrated the presence of a variety of amino acids in the Ivuna and Orgueil meteorites (Ehrenfreund et al., 2001). If the presence of biomolecules on the early earth is due in part to the bombardment of interplanetary dust particles, comets, and meteorites, then the same phenomenon could be taking place in any other solar system. 

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