March 14, 2006 | David F. Coppedge

Stardust Finds Burnt Rock in Comet Dust

In a surprise upset, scientists analyzing cometary material returned from the Stardust mission found minerals that must have glowed white-hot when they formed.  Comets were long thought to have formed in the outer fringes of the solar nebula or in the Oort Cloud, far from the sun where it’s icy cold and calm.  They were supposed to represent pristine material from the time before planets formed.  Whether this glazed material found in Comet Wild 2 fragments represents later processing as the comet neared the sun, or means that solar nebula material involved a great deal of mixing early on (meaning that no unprocessed material remains), or formed around other stars – or some other possibility – will require additional study.  Sources: BBC News, National Geographic, University of Washington and JPL press releases.  The later states, “Comets, they said, may not be as simple as the clouds of ice, dust and gases they were thought to comprise.  They may be diverse with complex and varied histories.”  The scientists found olivine (common to volcanic lavas), and “exotic, high-temperature minerals rich in calcium, aluminum and titanium.”  According to the BBC article, the two leading theories are (1) that the material was cooked by other stars, or (2) that it was cooked by the sun then blasted to far distances by a so-called “X-wind” process.  But Stardust co-investigator Mike Zolensky admitted, “This raises as many questions as answers.  We can’t answer them all just yet.”

For years—for decades—they have been telling us that comets held the secrets to the early solar system.  Drifting in the dark cold of the outer realms of the sun, comets were supposed to have accreted slowly from the original dust and ice of a molecular cloud.  They only neared the sun when perturbed by a passing star and were flung into the sun’s neighborhood.  This thinking has its origin in Laplace’s Nebular Hypothesis of the late 1700s.  Today’s news is a complete turnaround.  Now we have actual material from a live comet, showing that at least some of the material was so hot it was incandescent.  Some of the material looks like it was born in the fires of a rocky planet.  What Stardust has found will rewrite the textbooks and renders many a TV documentary obsolete.  An ounce of data is worth a ton of speculation.  That’s why the public should support sample-return and onsite-reconnaissance missions like Stardust, regardless of their opinions on origins and ages of things, if for no other reason than the entertainment of watching experts squirm.

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