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Updated 8:30 AM June 1, 2004



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Comets could provide link to birth of solar system

The study of comets is important because it is as close as scientists have come to finding material that formed the solar system, says a U-M scientist.

Michael Combi, research professor in the Department of Atmospheric, Oceanic and Space Sciences, and distinguished research scientist in the Space Physics Research Lab, delivered the 2004 University Distinguished Research Scientist Lecture May 12.

Combi discussed "Doing Research in a Coma: Or Understanding the Very Thin Atmospheres of Comets."

"Comets were formed with the solar system 4.5 billion years ago," he said. "And they may retain vestiges of the original interstellar material, out of which the solar system was formed."

Combi said most comets are similar to small, dirty snowballs that are 1-10 kilometers in size. He said they orbit around the sun, like the planets, but in an elliptical pattern. As comets get closer to the sun, the melting of the core forms a large, thin atmosphere—the coma or head—that is several times larger than the Earth, he said.

"What does a handful of one look like, what is the actual structure of the nucleus, and what does the distribution of the material look like?" Combi asked, echoing some unanswered questions in comet research. He said the Rosetta Orbiter launched earlier this year will attempt to put a lander on Comet 67P/Churyumov-Gerasimenko in 2014.

Comets often collide, he said, sending materials toward Earth, where scientists can study them. Some comets fall into planets. He showed photos of Shoemaker-Levy 9, which crashed into the surface of Jupiter July 16-22, 1994. He said several comets have fragmented in recent years, including Hyakutake in 1996 and Linear in 2000.

Combi received the Distinguished Research Scientist Award in September and will hold the associated title as long as he is at the University.

The award recognizes a research scientist or senior research scientist for exceptional scholarly achievement: the discovery and dissemination of new knowledge, the development of innovative technology, or the development of concepts that lead to significant advances in science, education, health, the arts or humanities.

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