Origins of life on earth found in Australian meteorite
The researchers examined material from three meteorites – one that fell in 1969 near the town of Murchison in Victoria, Australia, one that fell in 1950 near the town of Murray in Kentucky, and one that fell in 2000 near Tagish Lake in Canada’s British Columbia province.
All three are classified as carbonaceous chondrites, made of rocky material thought to have formed early in the solar system’s history. They are carbon-rich, with the Murchison and Murray meteorites containing about 2 per cent organic carbon by weight and the Tagish Lake meteorite containing about 4 per cent organic carbon. Carbon is a primary constituent of organisms on Earth.
“All three meteorites contain a very complex mixture of organic molecules, most of which have not yet been identified,” Glavin said.
Earth formed roughly 4.5 billion years ago. In its infancy, it was pelted by meteorites, comets and other material from space. The planet’s first organisms were primitive microbes in the primordial seas, and the earliest-known fossils are marine microbial specimens dating to roughly 3.5 billion years ago, though there are hints of life in older fossils.
The two nucleobases, called cytosine and thymine, newly identified in the meteorites may have eluded detection in previous examinations because they possess a more delicate structure than the other three, the researchers said.
The five nucleobases would not have been the only chemical compounds necessary for life. Among other things needed were: amino acids, which are components of proteins and enzymes; sugars, which are part of the DNA and RNA backbone; and fatty acids, which are structural components of cell membranes.
“The present results may not directly elucidate the origin of life on the Earth,” Oba said, “but I believe that they can improve our understanding of the inventory of organic molecules on the early Earth before the onset of life.”