Comets join meteors as a potential source of life on Earth

Ars Technica : How life began on Earth remains an open question. One promising theory is that meteors slamming into Earth could have produced enough energy to cause simple chemicals on the planet’s surface to form amino acids and other fundamental building blocks. Experiments over the past 50 years have shown that theory to be possible. Mark Price of the University of Kent, England, and his colleagues have now shown that comets could also have supplied not just the energy to make the molecular precursors of life, but also the reactants. To simulate comet impacts, they fired tiny bullets at 7150 m/s (16 000 mph) at blocks of ice made of methanol, carbon dioxide, and ammonia. The unreacted chemicals were then evaporated away. What remained was a collection of amino acids that included glycine and alanine—common building blocks of many proteins—and four other amino acids not found in life on Earth. The nature and proportions of the chemicals created suggests that they were formed as a result of the extreme impact pressure, which allows oxygen to join with methanol to form the compounds that then join to create the amino acids. There is still no conclusive evidence regarding the source of amino acids and other building blocks of life on Earth, but it now appears that comets could have been one of many contributors.