[meteorite-list] PSI Research Points to Better Understanding of Carbon in Comets

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 13 Dec 2010 10:59:53 -0800 (PST)
Message-ID: <201012131859.oBDIxrRD028234_at_zagami.jpl.nasa.gov>

NEWS RELEASE FROM THE PLANETARY SCIENCE INSTITUTE

SENT:
Dec. 13, 2010

FROM:
Alan Fischer
Public Information Office
Planetary Science Institute
520-622-6300
520-885-5648
fischer at psi.edu

PSI Research Points to Better Understanding of Carbon in Comets

Using a comet as a far-flung laboratory, a Planetary Science
Institute researcher has shown that the ionization lifetime of
carbon is much shorter than what is currently used in calculations
by comet scientists.

An accurate ionization lifetime is critical to understanding the
amount of carbon released from comets, said Jeff Morgenthaler,
senior scientist at PSI. A shorter lifetime suggests that the
carbon content of some comets may be lower than previously
estimated. This work could affect current ideas about where
comets formed in the early solar system and the role they may
have played in bringing the seeds of life to Earth.

"Carbon is an important atom for lots of reasons," Morgenthaler
said. "We need to know how much carbon there is in comets and in
what molecules it can be found to answer some of the questions
that have been posed."

Using wide-field images recorded by the Galaxy Evolution Explorer
(GALEX) satellite, Morgenthaler produced extremely high-quality
radial profiles of atomic carbon emissions from comet C/2004 Q2
(Machholz).

Unlike conditions seen on Earth, a comet's coma, or envelope
around its nucleus, is a very simple atmosphere with no gravity
and no magnetic field, and is only affected by the solar photon
and solar wind environment, Morgenthaler said.

"Since other researchers have established how fast the carbon
moves away from the comet, we could use the fall-off of the light
as a function of distance to measure how long the carbon lives in
the interplanetary medium before it is ionized," said Morgenthaler,
lead author of a recent paper on the topic that appeared in the
Astrophysical Journal.

"We got a chance to check a lot of calculations at once with our
measurement," he said. "We found that a carbon atom is ionized
after seven to 16 days, depending on solar activity and solar
wind conditions."

This marks the end point of the destruction of all of the more
complex carbon-bearing molecules found in comets.

Researchers have used the presence of long-chain carbon-containing
molecules in comets, including some simple amino acids, as evidence
that comets may have brought the seeds of life to Earth. "We need to
pull back a few more layers of the onion to see if the signatures of
the long-chain carbon-bearing molecules are detectable in these data,"
Morgenthaler said. "We definitely see the signatures of carbon
monoxide and methane."

The research found that more than just sunlight was affecting the
carbon from the comet.

"Something was hitting the carbon: the solar wind," he said. "This
had been predicted earlier, but until now no one had quantitatively
put all the pieces together and done a measurement that confirmed it."

The research was funded by a grant to PSI from the GALEX Guest
Investigator program.

GALEX's wide field of view at 1 degree is 10 times larger than the
typical ultraviolet telescopes used for similar research, he said.
This allows GALEX to capture essentially all the emission from the
comet, resulting in far more accurate results.

Co-authors of the Astrophysical Journal paper are Walter M. Harris,
Department of Applied Sciences, University of California at Davis;
Michael R. Combi, Department of Atmospheric, Oceanic and Space
Sciences, The University of Michigan; Paul D. Feldman, Department
of Physics and Astronomy, The Johns Hopkins University; Harold A.
Weaver, Space Department, Johns Hopkins University Applied Physics
Laboratory.


CONTACT:
Jeff Morgenthaler
Senior Scientist
207-231-4036
jpmorgen at psi.edu


PSI INFORMATION:
Mark V. Sykes
Director
520-622-6300
sykes at psi.edu
Received on Mon 13 Dec 2010 01:59:53 PM PST