Viewing A Comet Up Close And Personal

By James Donahue

When I was a kid gazing with awe at the stars, I never dreamed that we might have the technology to send a camera attached to a rocket to other planets and certainly not to a passing comet.

But that is what recently happened. To me, the fact that we photographed comet “Wild 2” up close is still an awe-inspiring event, although the media treated it as if it was but a novelty. Something unique to capture a news hole for the day and then to be forgotten.

I’m sure a few NASA scientists and other astronomers didn’t think of it that way.

Comets have always been among the mysteries of space. They seem to travel in their own orbital path, some of them visiting our solar system once in long periods of time, perhaps 50 to 100 years. Others come and go once in recorded history.

That they light up the sky in their passing, usually spewing a long lighted tail, only adds to the lure of watching comets come and go.

Questions like what comets are made of, where they come from, why they assume such wide orbits and why they spit out material that glistens as a passing tail, obviously prompted scientists to send the Stardust spacecraft off in 1999 to get a close-up look at Wild 2 as it passed through our solar system.

Not only did Stardust get close-up pictures of this comet, it also scooped up samples of the “dust” and is scheduled to bring it back for analysis by sometime in 2006.

What the pictures showed at fly-by left more questions than answers. The comet appeared as a solid object, with broad mesas, craters, pinnacles and canyons. But it also was spitting out material at supersonic speeds from jets clearly visible on the comet’s surface.

In a paper published in the journal Science, Astronomer Donald Brownlee of University of Washington, described what he said was an unexpectedly chaotic distribution of dust particles flying off the comet.

Brownlee described the nucleus of the comet as a clump of hard dirt that reacts to particles that strike it because there is no gravity to keep the dust on its surface.

But if he is right, how can scientists say that a big lump of dirt, flying at such speed through the universe, is billions of years old?

While we now have a description of a comet, Stardust has done little to really explain what it is, what it is made of, and why it does what it does.

But then, it is always fun to have a few mysteries around to keep us guessing.