NASA Captures Photos of Comet Hartley 2 Creating Snowstorm

(Nov. 18) -- A NASA spacecraft has captured dramatic images of a comet creating its very own snowstorm, a swirling blizzard containing globs of snow as big as basketballs.

"To me this whole thing looks like a snow globe that you've just simply shaken," Brown University's Pete Schultz, one of the scientists analyzing the new footage of the comet, Hartley 2, said at a news conference today. When researchers saw the first clear images, "our mouths just dropped," he said.

"We realized we had a cloud of snow around the nucleus," or center, of the comet, said chief scientist Michael A'Hearn of the University of Maryland. "We were astounded."

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Snowstorm in Space

Never before have individual chunks of ice been seen around a comet.

The photos of the comet hurtling through flurries of its own making were snapped as the spacecraft sped close to the comet in early November, approaching less than 500 miles from the comet's center. Engineers chose that distance in part to keep the spaceship safely away from debris spewed by the comet. They miscalculated.

Engineers estimate that as many as nine particles from the comet hit the spacecraft, said the spacecraft's manager, Tim Larson of NASA's Jet Propulsion Laboratory in Pasadena, Calif. The biggest particles weighed about as much as an eyelash, so the ship did not sustain any damage.

The "snowballs" are made of tiny flakes of frozen water that have clumped together very loosely, said astronomer Jessica Sunshine of the University of Maryland. Rather than being hard-packed lumps of ice, the snowballs have a structure closer to that of a "dandelion puff," she said.

Scientists have long known that this comet, named Hartley 2 after its discoverer, is small, odd and eruptive. But the new photos show a body even stranger than they'd suspected. The comet has an unusual peanut shape, with bright jets of gas and dust dancing off its surface.

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The latest analysis shows that water vapor is wafting off the peanut's "waist," while carbon dioxide gas squirts out from the two lobes on the end, the scientists said today. The carbon dioxide drags dust and snow particles from the interior of the comet into space.

The results mean that Hartley 2 was cooked up from a different recipe than other comets. Comets were born in the early years of the solar system more than 4 billion years ago, but it's turning out that they don't look anything like one another despite their shared birthday.

Hartley 2's close-up was snapped by a grizzled old spacecraft called Deep Impact. Deep Impact is the first ship to have taken photos of two comets, having swung by a much less dramatic comet called Tempel 1 in 2005.

"I used to have a favorite comet. It was called Tempel 1," Sunshine said. "Now we have a new favorite -- Hartley 2."