[meteorite-list] NASA Identifies Carbon-rich Molecules in Meteors as the 'Origin of Life'
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 25 Sep 2008 13:24:48 -0700 (PDT)
NASA Identifies Carbon-rich Molecules in Meteors as the 'Origin of Life'
September 24, 2008
Tons, perhaps tens of tons, of carbon molecules in dust particles and
meteorites fall on Earth daily. Meteorites are especially valuable to
astronomers because they provide relatively big chunks of carbon
molecules that are easily analyzed in the laboratory. In the past few
years, researchers have noticed that most meteorite carbon are molecules
called polycyclic aromatic hydrocarbons (PAHs), which are very stable
compounds and are survivors.
PAHs are the most common carbon-rich compound in the universe. They are
found in everything from distant galaxies to charbroiled hamburgers and
engine soot. When they are first formed, or found in space, their
structures resemble pieces of chicken wire, fused six-sided rings.
However, when found in meteorites, these aromatic rings are carrying
extra hydrogen or oxygen.
Scientists at NASA Ames Research Center, Moffett Field, Calif. performed
laboratory experiments that explain the process by which these
meteoritic hydrocarbons attract the extra hydrogen and oxygen. They are
very similar to the molecules identified as evidence of alien microbes
in an earlier Science paper (McKay et al 1996).
???Our findings are important because it is the first time anybody
explained these carbon-rich molecules found in meteorites. They are
similar to the molecules that make-up living things,??? said Max
Bernstein, a space scientist at NASA Ames.
As it happened, their findings were judged significant enough to be
award-winning. Published in Science (1999) by Bernstein and fellow NASA
Ames scientists Scott Sanford and Louis Allamandola, their paper won the
2008 H. Julian Allen Award at NASA Ames Research Center.
It takes a long time for scientific papers to win awards.
"As scientists, we like to quantify things. Scientific papers are judged
by the number of times they are cited in other scientific papers. Other
scientists need to say that I couldn't have written my paper without
your paper. Often it takes a few years," Bernstein explained.
These carbon-rich molecules are produced by carbon-rich, dying, giant
red stars. When they are first formed, astronomers observe them as
normal PAHs. However, when they are seen in meteorites billions of years
later, they almost always have oxygen or heavy hydrogen attached to
them. (Heavy hydrogen carries an extra neutron, and is called a
deuterium isotope.) Something happened to change them, say scientists.
To study the process by which these carbon compounds change, the Ames
Astrochemistry Laboratory studied PAHs in water ices that were exposed
to ultraviolet radiation under space-like conditions. Scientists
reproduced conditions including an incredibly high vacuum, extremely low
temperatures (- 340 degrees Fahrenheit), and harsh radiation. When the
extremely cold temperature was reached, these PAHs were exposed to
ultraviolet radiation, and they changed. The experiment successfully
reproduced the hydrocarbons found in meteorites. For the first time,
scientists were able to show how hydrogen was exchanged for deuterium,
or heavy hydrogen.
"It turns out, you only need water ice and radiation to change these
molecules," said Bernstein.
Using infrared spectroscopy, the Ames research team proved that the
laboratory-produced hydrocarbons were the same hydrocarbons found in
meteorites and observed through telescopes. Scientists observed the
chemical reaction in a stainless steel chamber as it was happening. The
laboratory sample reflected the same infrared colors as the hydrocarbons
seen by astronomers using telescopes. Because the techniques used were
the same, the results were directly comparable. "We were seeing the same
molecules from telescopes as were reproduced in the laboratory," said
Once the molecular-size laboratory sample was retrieved, it was taken to
Richard Zare's laboratory at Stanford University, where researchers
weighed the individual molecules. Findings showed that ices, modified by
radiation, created new molecules.
These molecules, called quinones, received considerable attention by the
astrobiology community because they are common to all life forms. They
are potentially significant for the "origin of life" or the habitability
of planets. How does a planet become habitable?
"Molecules from space helped to make the Earth the pleasant place that
it is today," said Allamandola, founder of the Ames Astrochemistry
"Our findings were new because we showed how these molecules formed. It
was already known that these molecules were in meteorites and delivered
to the planets," said Bernstein.
"We now understand why these life-like carbon compounds are raining down
on the Earth and other planets. Knowing this will help us search for
life on other worlds by distinguishing these molecules from biomarkers,"
For further information, please read: Bernstein, Max P., Scott A.
Sanford, Louis Allamandola, J. Seb Gillette, Simon J. Clemett and
Richard N. Zare. "UV Irradiation of Polycyclic Aromatic Hydrocarbons in
Ices: Production of Alcohols, Quinones, and Ethers" Science 283 (1999):
1135 - 1138
McKay, David S., et al. "Search for Past Life on Mars: Possible Relic
Biogenic Activity in Martian Meteorite ALH84001" Science 273 (1996):
For further NASA and Ames Astrochemistry Laboratory information, please
Ruth Dasso Marlaire
NASA Ames Research Center, Moffett Field, Calif.
Received on Thu 25 Sep 2008 04:24:48 PM PDT