NASA’s EPOXI mission provided this enigmatic view of Hartley 2, a bowling-pin shaped comet barely a mile in diameter. The image shows jets of carbon dioxide on the comet’s dark face. The particles visible to the left are chunks of carbon dioxide ice; mission planners say that the EPOXI probe was pelted with these light, fluffy snowballs, some the size of basketballs, as it approached to within 430 miles of the comet on November 4.
This is EPOXI’s second visit to a comet; in 2005 it visited the much larger 9P/Tempel, which it struck with an instrument called an “impactor” in order to reveal aspects of the comet’s structure. It has also been used to investigate newly-discovered planets orbiting stars more than 1000 light years from our sun. It’s recycling in space—mission planners have been retooling and reprogramming on the fly to use the probe’s instruments to do all kinds of science not intended when the vehicle went aloft under the name Deep Impact in 2005. Along the way, it managed to capture this stop-motion image of the moon transiting Earth: