No “typical” comets, astronomers suggest based on comet-shoot study
July 2, 2005
Courtesy Queen's University
and World Science staff
After two months of studying data from an experiment that involved shooting a projectile at a comet, astronomers are revealing new findings about what the test revealed.
Among the more important of these revelations: there may be no such thing as a “typical” comet, 35 astronomers said in a paper published in the upcoming Sept. 9 edition of the research journal Science.
The astronomers noted that the comet is very different from two other closely-studied comets believed to come from the same area of space. This “raises the question of whether any comet is typical when looked at closely,” the researchers, led by Michael A’Hearn of the University of Maryland in College Park, Md., wrote.
The comet in the projectile experiment, Tempel 1, “is the first comet to show evidence for
impact craters,” and the elongated shape of its core is also different, they added.
Tempel 1 also seems to have a fine powder covering its surface to a depth of tens of meters, the researchers added, with ices slightly below this surface, and it appears to contain many organic molecules—the ingredients of life.
Astronomers wanted to study a typical comet when they chose Tempel 1 as the target of a projectile size of a washing machine, which hit its surface on July 4. The purpose of the experiment was to watch the explosion resulting from the blast and see if it revealed anything about the comet’s structure.
Tempel 1 is believed to be about half the size of Manhattan and to come from the Kuiper belt, a disc-shaped region of comets and asteroids that lies beyond Neptune’s orbit and extends out for several hundred times the Earth-Sun distance.
It was hoped that the impact would eject material from the surface of the comet and reveal the pristine material beneath. This is believed to be material left over from the Solar System’s formation 4˝ billion years ago.
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