The European Space Agency, and in particular the ESA member states that chose to participate in the Rosetta comet-chaser mission, received a large and well-deserved dose of satisfaction Aug. 6 when the spacecraft finally arrived within striking distance of its destination. After a journey of more than 10 years following a combined investment of $1.75 billion, Rosetta is now within 100 kilometers of Comet 67P/Churyumov-Gerasimenko and has sent back stunning images that are already changing the way scientists think about these mysterious objects. It has been widely assumed that comets are giant, dirty slush balls, but based on initial assessments of Rosetta's data Comet 67P appears to more rocky than icy.
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