archive: SETI [ASTRO] Carbon Offers Glimpse Of Origin And Evolution Of The

SETI [ASTRO] Carbon Offers Glimpse Of Origin And Evolution Of The

Larry Klaes ( )
Wed, 23 Dec 1998 15:37:46 -0500

>X-Authentication-Warning: majordom set sender
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>Date: Wed, 23 Dec 1998 17:15:24 GMT
>From: Ron Baalke <>
>Subject: [ASTRO] Carbon Offers Glimpse Of Origin And Evolution Of The
>Reply-To: Ron Baalke <>
>Kathleen Burton
>NASA Ames Research Center Dec. 18, 1998
>Moffett Field, CA
>(Phone: 650/604-1731)
>Scientists at NASA's Ames Research Center, Moffett Field, CA, collaborating
>with the Astrophysikalisches Institut in Germany, have demonstrated that
>organic chemistry is abundant in the universe, implying that carbon-based
>life could be possible throughout the universe.
>In a paper published in the December 18th issue of Science entitled "Carbon
>in the Universe," Thomas Henning of the Astrophysikalisches Institut in
>Jena, Germany and Farid Salama of NASA Ames report finding the unique
>signatures of an exotic form of carbon in deep space.
>Known as PAHs (short for polycyclic aromatic hydrocarbons), these
>carbon-based molecules, shaped like fragments of chicken wire, are thought
>to be ubiquitious in space. The existence of PAHs in the interstellar medium
>(ISM) may explain the mysterious spectral signatures that are common
>throughout interstellar space.
>"Understanding the makeup of the ISM will help us better understand the
>origin and evolution of life in the universe," said Farid Salama, the
>paper's co-author. "It is a key issue for astrobiology and could demonstrate
>that life's essential, pre-biotic, carbon-based building blocks are abundant
>in the ISM."
>Without carbon, life as we know it would not exist. The element plays key
>roles in the evolution of stars, planets, and human bodies because it is
>abundant and can form complex structures.
>The paper reviewed how the study of cosmic carbon has provided clues to the
>solar system's origins, the introduction of life to Earth, and the very
>structure of the universe. Stars create carbon in their interiors and
>release it into space, making carbon an ideal probe and tracer of the birth
>and death of stars and planetary systems and of the processes in deep
>interstellar space.
>This research also helps solve a problem scientists have struggled with for
>most of the century. They have detected more than 100 interstellar
>absorption lines in the spectra (range of frequencies or color) of starlight
>approaching the Earth. The lines are called diffuse interstellar band
>(DIBs). Scientists believe a form of PAHs might be the long-sought matter
>producing the interstellar bands.
>Absorption lines are discrete colors of light that are absorbed by
>intervening matter; this absorption leaves holes or "lines" in the spectral
>PAHs, thought to be formed in a star's atmosphere, are stable carbon
>molecules formed at high temperatures that can withstand the intense
>radiation and harsh environment of interstellar space. On Earth, they cause
>pollution and cancer. PAHs are found in diesel exhaust, burned pots and
>pans, charred hamburgers and cigarette smoke.
>Simulating the conditions of space, Ames scientists measured the spectra of
>large, carbon-bearing molecules in the UV and visible light bands and
>compared it to astronomical data from Kitt Peak and other observatories. The
>scientists simulated the space environment using extreme cold, a near-vacuum
>and artificial starlight.
>The next phases, Salama said, are to continue the research using a more
>sensitive gas-based measuring technique which almost precisely approximates
>interstellar conditions.
>The Astrophysikalisches Institut explored the problem by studying larger
>grain-sized carbon, another type of carbon material produced by stars. "I'm
>a big fan of science collaboration," said Salama. "It helps push the
>boundaries of science, generates new ideas and speeds up the process."