WASHINGTON (Reuters) - The disintegration of a comet's icy heart in Earth's neighborhood offers tantalizing clues to how our solar system came together, scientists reported on Thursday.
Astronomers had a ring-side seat in July when Comet LINEAR literally fell apart about 37 million miles from Earth, a mere stone's throw in cosmic terms.
What they saw was unique, according to Hal Weaver, a researcher at Johns Hopkins University and author of three of six papers on the comet's demise published in the current edition of the journal Science.
Instead of dying by collision after being pulled toward a much larger body, as Comet Shoemaker-Levy did in 1994 when it smashed into Jupiter, LINEAR disintegrated in space, leaving behind tiny particles spread out over 62,000 miles as well as 16 big chunks up to 330 feet across.
What disappeared was the nucleus of the comet, what scientists believe is a "dirty snowball" made up of frozen water and other ice and bits of rock and dust.
ODD BEHAVIOR
"I've never seen another comet behave this way," Weaver said in a telephone interview. "It was a puzzle as to why it came apart so dramatically.... I have never seen a comet nucleus that has come apart where the nucleus seemed to disappear."
Astronomers study comets because they are believed to be some of the remnants of the formation of the solar system, and may offer evidence about how the sun, planets and other features came to be.
The death of LINEAR was especially interesting, Weaver said because scientists may be able to look at the comet's demise as they would a movie running backward, to reconstruct what may have happened at the solar system's birth.
"By watching the comet come apart, we were hoping it was like hitting the rewind button and allowing us the opportunity to see how it formed," Weaver said in a statement.
But he said this would not be known until scientists determine what caused the comet to break up.
LINEAR seemed to break apart in stages, which suggests that heating by the sun did not make it explode. Instead, Weaver said, the comet may have died due to fast rotation, smashups with asteroid debris or a combination of the two.
Comets are some of the most primitive bodies in the solar system, and LINEAR is believed to date back an estimated 4.6 billion years. It was first spied in 1999 when it was heading toward the Sun from a region out by Jupiter and Saturn.
The Hubble Space Telescope snapped fiery-looking images of the comet's death and aftermath. The pictures can be seen at http://oposite.stsci.edu/pubinfo/PR/2000/27/content/0027a.jpg, or through links from the main Hubble site, http://www.stsci.edu/.
©Reuters May 17 2001 3:01PM