IN NOVEMBER the public’s imagination was briefly caught by the adventures of a plucky little spacecraft called Philae. This craft, the pup of a mother ship known as Rosetta, made a bouncy landing onto the surface of comet 67P/Churyumov-Gerasimenko, whichRosetta was orbiting. Philae worked for but a couple of days, and after it died attention turned elsewhere. But Rosetta has continued to operate, and her reports have now been distilled into a series of papers, just published in Science, that give a preliminary assessment of what the two craft have found.
The comet’s surface, as Nicolas Thomas of the University of Bern has discovered, is surprisingly complex. It has 19 distinct regions, characterised by features such as pits, wide depressions and smooth, dust-covered plains. It even sports things that look like sand dunes.
The reason for that shape, though, remains a mystery. Possibly, Dr Sierks speculates, Churyumov-Gerasimenko is made up of two comets which have collided and joined together. Determining the truth of this will require further investigation.The surface is also, according to Fabrizio Capaccioni of the National Institute of Astrophysics, in Rome, drier than expected and rich in organic compounds. That may excite those who wonder how the chemicals needed for life’s development arrived on Earth. The comet’s interior, meanwhile, says Holger Sierks of the Max Planck Institute for Solar System Research, in Göttingen, Germany, has only half the density of water. It is therefore probably porous and fluffy. And it ejects jets of material into space (see picture above), particularly from the neck that connects the two halves of the comet’s peculiar dumbbell shape.