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Chemistry Of Comet Hale-Bopp May Offer Clues About Early Solar System

News Office
University of Massachusetts-Amherst

Contact: Elizabeth Luciano, luciano@admin.umass.edu

Release: Oct. 13, 1999

CHEMISTRY OF COMET HALE-BOPP MAY OFFER CLUES ABOUT THE EARLY SOLAR
SYSTEM, UMASS ASTRONOMER SAYS

Findings to be presented at meeting of the American Astronomical Society

AMHERST, Mass. -- A group of astronomers led by William Irvine of the
University of Massachusetts has discovered that a new molecule, nitrogen
sulfide (NS), is contained within comets. Although scientists have long
known that the molecule exists within dense interstellar clouds, this is
the first time it has been seen in a comet. The findings are being presented
during the annual meeting of the Division of Planetary Sciences of the
American Astronomical Society, currently underway in Padua, Italy.

"The finding is significant," Irvine explains, "because astronomers believe
that comets hold the best samples of materials from which the solar
system was formed." Comets are icy masses which appeared in the outer
regions of the solar system when it was formed, 4.5 billion years ago.
Their distance from the sun has resulted in comets being heated only
minimally, preserving frozen gases that may give scientists clues about
what materials existed in space when the solar system formed.

The astronomers made the observation in March 1997, while conducting
separate research using the James Clerk Maxwell Telescope on Mauna Kea
Mountain in Hawaii. Collaborators on the project were Henry Matthews,
Joint Astronomy Center, in Hilo, Hawaii; Roland Meier, of the Institute
for Astronomy, University of Hawaii; Irvine, Matthew Senay, and Ricardo
Metz, of UMass; and Douglas McGonagle, formerly of UMass. The research
was sponsored in part by NASA.

The compound is the only known molecule in comets that contains both
nitrogen and sulfur. The molecule is a "radical," which means that it's
highly reactive, chemically. The discovery raises the question of whether
the NS in Comet Hale-Bopp has existed since the start of the solar system,
or if it was produced as a result of other compounds in the comet breaking
apart. Scientists will be able to determine that, Irvine said, by examining
exactly where in comets the NS lies. An abundance in the head, or nucleus,
would suggest original material, but the amount cannot be measured from
Earth. The way in which the abundance of NS varies in the comet's
atmosphere, called the coma, would indicate whether the molecule is the
result of other compounds breaking apart due to the effect of sunlight,
or whether it was produced by chemical reactions. To make such a
determination, the NS molecule must be found in other comets.

The discovery is further intriguing because scientists have long suspected
that many molecules on Earth were brought here by comets. "Could
comets have provided molecules that became part of the oceans and the
atmosphere?" Irvine asks. "Could this material perhaps even be relevant
to the origin of life?"

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