Pre-life molecules present in comets
University of Michigan News Release
July 21, 2006
ANN ARBOR, Mich. - Evidence of atomic nitrogen in interstellar gas clouds
suggests that pre-life molecules may be present in comets, a discovery
that gives a clue about the early conditions that gave rise to life,
according to researchers from the University of Michigan and the
Harvard-Smithsonian Center for Astrophysics.
The finding also substantially changes the understanding of chemistry in
The question of why molecular nitrogen hasn't been detected in comets
and meteorites has puzzled scientists for years. Because comets are born
in the cold, dark, outer reaches of the solar system they are believed
to be the least chemically altered during the formation of the Sun and
Studies of comets are thought to provide a "fossil" record of the
conditions that existed within the gas cloud that collapsed to form the
solar system a little more than 4.6 billion years ago. In this cloud,
since nitrogen was thought to be in molecular form, and it follows that
comets should contain molecular nitrogen as well.
But the reason it isn't there is because it isn't present in the gas
clouds whose microscopic solid particles eventually form comets, said
Sebastien Maret, research fellow in astronomy at the University of
Michigan, and Edwin Bergin, a professor of astronomy at the University
of Michigan. Those clouds contain mostly atomic nitrogen, not molecular
nitrogen, as previously thought.
Maret, Bergin, and collaborators from Harvard-Smithsonian Center for
Astrophysics will publish their findings in the July 27 issue of the
The nitrogen bearing molecules in comets that crashed into Earth
millions of years ago may have provided a sort of "pre-biotic jump
start" to form the complex molecules that eventually led to life here,
"A lot of complex and simple biotic molecules have nitrogen and it's
much easier to make complex molecules from atomic nitrogen," Bergin
said. "All DNA bases have atomic nitrogen in them, amino acids also have
atomic nitrogen in them. By that statement what we're saying is if you
have nitrogen in its simplest form, the atomic form, it's much more
reactive and can more easily form complex prebiotic organics in space."
These complex organics were incorporated into comets and were provided
to the Earth.
"What we're seeing in space is telling us something about how you make
molecules that led to us," Bergin said.
Also of importance is the fact that odd anomalies in isotopic values in
meteorites can also be explained if the nitrogen is not molecular,
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