Comet-Hunter Closing InAfter a nearly 2.9-billion-mile (4.6-billion-kilometer) voyage, NASA's EPOXI mission spacecraft has survived its risky rendezvous with comet 103P/Hartley 2 and has beamed back the first close-up images of the comet.
This montage of five pictures, for example, shows Hartley 2's nucleus as the craft was flying toward and under the icy body on Thursday. The images progress in time clockwise, starting at top left.Initial views of Hartley 2 show a comet the likes of which mission scientists have never seen before, including an odd peanut or bowling pin shape and dozens of superactive jets spewing gas and dust like firehoses.The odd textures of the surface of the nucleus—visible in the images above—have also caught many experts' eyes: The thick, rough ends of the comet are bisected by a much thinner central region that is noticeably smoother."We think the jet activity at the ends of the nucleus run along natural ridges, and may end up eroding the surface and creating clumps of material at the far ends of the comet," said Jessica Sunshine, EPOXI team scientist."In the center there doesn't seem to be any jet activity at all, creating a possible natural reservoir." Sunshine speculates that the smooth region may be filled with fine grains of dust that originated from the active regions near the comet's poles and were drawn by gravity to the middle.(See more pictures of comet Hartley 2.)—Andrew Fazekas

Photograph courtesy NASA/JPL-Caltech/UMD