Developments in Brief : Meteorite Supports Life in Space Theory

A new Caltech analysis of organic chemicals found on a meteorite that fell in Australia in 1969 indicates that the compounds originated in space, not on Earth. The results provide new support for the theory that many of the basic building blocks of life are formed in the vast spaces between the stars.

Such a finding reinforces suggestions that life exists elsewhere in the universe.

To date, 55 amino acids have been identified in the meteorite, which landed near Murchison, Australia, 18 years ago. Eight of these amino acids are normal constituents of the proteins found in all life, and 11 are rare amino acids that occur in biological systems, but not in proteins. The remainder may be unique to meteorites.

Caltech geologist Samuel Epstein and geochemist R. V. Krishnamurthy, working with colleagues at Arizona State University, analyzed the elemental composition of the amino acids, looking particularly at isotopes of hydrogen and nitrogen that are heavier than the normally occurring forms.

These isotopes, called deuterium and nitrogen-15, are rare on Earth but are found in much higher concentrations in interstellar clouds. Epstein’s group found that their incidence in the amino acids from the meteorite matched the concentrations found in space, not those found on Earth. This evidence supports the theory that the amino acids originated in space, which suggests that life may occur elsewhere in the universe.