[meteorite-list] New Method Uses Visible & Ultraviolet Spectroscopy to Study Comet Composition

[Ron Baalke]

University of California-Davis

Media Contacts:
William Jackson, UC Davis Chemistry
(530) 752-0504, wmjackson at ucdavis.edu

Andy Fell, UC Davis News Service
(530) 752-4533, ahfell at ucdavis.edu

FOR IMMEDIATE RELEASE: August 9, 2004

What is a comet made of?
   	
A new method for looking at the composition of comets using ground-based 
telescopes has been developed by chemists at UC Davis. Remnants from the 
formation of our solar system, the makeup of comets gives clues about how the 
Earth and other planets formed.

William Jackson, professor and chair of chemistry at UC Davis; researchers 
Alexandra Scodinu and Dadong Xu; and Anita Cochran of the University of Texas at 
Austin have developed methods to use visible and ultraviolet spectroscopy to 
study the chemical composition of comets.

Spectroscopy, a powerful technique in chemistry, splits light into a spectrum of 
color. Chemicals show a distinct pattern of peaks or lines in a spectrum. But 
the emission spectrum of comets in the visible and ultraviolet bands is full of 
thousands of lines, making it difficult to identify any one component.

The researchers took one suspected chemical, carbon disulfide, and used spectra 
measured in the laboratory under conditions similar to those in a comet. They 
compared this spectrum with that from comet 122P/De Vico to identify carbon 
disulfide in the comet. The spectrum of this molecule is such that it could not 
have been detected by other methods.

The technique makes it possible to look at the chemical composition of comets on 
their first visit to the inner solar system, which are difficult to reach with 
space probes and may have a different composition than comets that have been 
close to the sun many times, Jackson said. Detection of organic compounds such 
as benzene would show that these and more complex chemicals were present in the 
early solar system and could have contributed to the origins of life, he said.

The research is published in the June issue of the Astrophysical Journal.