[meteorite-list] NASA Reveals Key to Unlock Mysterious Red Glow in Space (PAHs)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 2 Aug 2010 11:10:18 -0700 (PDT)
Message-ID: <201008021810.o72IAIt3022274_at_zagami.jpl.nasa.gov>

Aug. 2, 2010

Ruth Dasso Marlaire????????????????????????????????????????????
Ames Research Center, Moffett Field, Calif.
650-604-4709
ruth.marlaire at nasa.gov

RELEASE: 10-65AR

NASA REVEALS KEY TO UNLOCK MYSTERIOUS RED GLOW IN SPACE

MOFFETT FIELD, Calif. -- NASA scientists created a unique
collection of polycyclic aromatic hydrocarbon (PAH) spectra
to interpret mysterious emission from space. Because PAHs
are a major product of combustion, remain in the environment,
and are carcinogenic, the value of this PAH spectral collection
extends far beyond NASA and astronomical applications.

For years, scientists have been studying a mysterious infrared
glow from the Milky Way and other galaxies, radiating from?
dusty regions in deep space. By duplicating the harsh conditions
of space in their laboratories and computers, scientists have
identified the mystifying infrared emitters as PAHs. PAHs are
flat, chicken-wire shaped, nano-sized molecules that are very
common on Earth.

"PAHs in space are probably produced by carbon-rich, giant stars.
A similar process produces soots here on Earth," said Louis
Allamandola, an astrochemistry researcher at NASA's Ames Research
Center, Moffett Field, Calif. "Besides astronomical applications,
this PAH database and software can be useful as a new research tool
for scientists, educators, policy makers, and consultants working
in the fields of medicine, health, chemistry, fuel composition,
engine design, environmental assessment, environmental monitoring,
and environmental protection."

To manage the research data, NASA built a database that now can be
shared over the internet. It's the world's largest collection of
PAH infrared data, and the website contains nearly 700 spectra of
PAHs in their neutral and electrically charged states. In addition,
it has tools to download PAH spectra ranging in temperature from
minus 470 to 2000 degrees Fahrenheit. Thanks to these spectra, PAHs
are now known to be abundant throughout the universe, but in exotic
forms not readily found on Earth.

This mysterious infrared radiation from interstellar space was
discovered in the 1970's and 1980's. While the infrared signature
hinted that PAHs might be responsible, laboratory spectra of only
a handful of small, individual PAHs were available to test this
idea. To make matters worse, these were only for neutral, solid
PAHs; they were not representative of PAHs found in space, where
they'd be electrically charged, very cold, individual molecules
floating in the gas.

By the mid-1990's, observations showed this infrared emission as
surprisingly common and widespread across the universe, implying
that the unknown carrier was abundant and important. To better
understand PAHs, then thought to be too complex to be present in
space, their spectra were measured under astronomical conditions.

To capture their spectra, Allamandola led a team of scientists to
measure PAH spectra under simulated astronomical conditions and
with computer software. This team consisted of experts in many
different fields.

"This group made a tremendous effort to make this a reality," said
Allamandola. "There are now nearly 700 spectra in the database. Six
hundred of these have been theoretically computed, and sixty have
been measured in the laboratory. The theoretical spectra span the
range from two to 2000 microns, the experimental spectra cover two
to 25 microns."

The spectra have given insights into the PAHs in space that were
impossible to get any other way. Scientists predict that in the
near future these spectra will be especially valuable for
interpreting observations made with NASA's new airborne observatory,
the Stratospheric Observatory for Infrared Astronomy (SOFIA) and
the recently launched European Space Agency's (ESA) Herschel
Telescope.?

They tried to make the website user friendly for researchers. One
can explore the database by charge, composition and spectral
signatures. Tools allow users to do analyses online. For example,
spectra can be combined to create a "composite" signature that can
be compared directly to the spectrum of "unknown" material.

We will expand the database and tools," said Christiaan Boersma, a
NASA postdoctoral fellow at Ames, who designed and developed many
parts of the website and tools. "We now use the database to
interpret astronomical observations from star and planet forming
regions in our galaxy, the Milky Way, and even other galaxies."

"Initially, our hope was to help interpret the experimental spectra,
but over time, our computational capabilities made it possible to
study molecules much larger than can be studied in the laboratory,"
said Charles Bauschlicher Jr., a world-renowned computational chemist
at Ames.

"Thanks to the great sensitivity of the Spitzer Telescope, PAHs are
seen across the universe, removing any doubt of the importance of
these species," said Allamandola.?

The database is available at http://www.astrochem.org/pahdb

More information about the database and graphics are available at
http://www.astrochem.org/pahdb/pressrelease

-end-
Received on Mon 02 Aug 2010 02:10:18 PM PDT