In June astrobiologists announced [pdf] they had found a key component of genetic material within a meteorite. The discovery supports the idea that asteroid bombardment four billion years ago may have jump-started the emergence of life.
Zita Martins of Imperial College London and her colleagues identified the organic molecules in the 4.6-billion-year-old Murchison meteorite, a carbon-rich rock that fell to Earth in Australia in 1969. Earlier researchers had detected subunits of DNA and RNA, called nucleobases, in the meteorite. But nobody could be sure whether the nucleobases were extraterrestrial or were simply soil contaminants.
Martins found the answer by extracting two molecules from the meteorite: uracil, a nucleobase found in RNA, and xanthine, an intermediate in the synthesis of DNA and RNA. She then compared the ratio of the two isotopes of carbon (carbon 13 and carbon 12) in them and found that the heavier carbon 13 predominated and matched ...
