NASA Probe Passes 'Snow Globe' Comet

NASA's Deep Impact probe soared past a comet earlier this month, revealing the mass to be peppered with "snowballs," the BBC reports. Comet Hartley, encountered some 14 million miles from Earth, "looks like a 'snow globe' that you've just simply shaken,” said a scientist. Another noted that the largest ice particles surrounding it “are at least the size of a golf ball and possibly up to the size of a basketball.”

But the "snowballs" are not big chunks of ice; instead, they're made up of tiny particles no bigger than one to 10 microns—a measurement roughly equivalent to “the thickness of our hair,” said another expert. “What we're seeing are fluffy aggregates of very small pieces of ice. They're akin more to a dandelion puff than an ice cube.” The Deep Impact probe will complete its observation of the mile-long, peanut-shaped comet at the end of next week; in total, it will have taken some 122,000 photos. (More Deep Impact probe stories.)