OSIRIS catches activity in the act

Rosetta’s scientific imaging system OSIRIS has witnessed a new jet of dust emerging from the surface of Comet 67P/Churyumov-Gerasimenko. The image was presented during the European Geosciences Union General Assembly, EGU, in Vienna last week. Sometimes it is all a matter of being in the right place at the right time. Or, as in the case of ESA’s space probe Rosetta, of opening your eyes at the exactly right moment. In mid-March, the OSIRIS camera was able to catch the elusive moment when a new dust jet from comet 67P/C-G burst into life. The comet’s activity has been significantly increasing over the last weeks and months. As the comet moves closer to the Sun along its orbit, its nucleus gets warmer and warmer. Frozen gases sublimate from its surface, carrying dust particles with it and enshrouding the nucleus in a dense coma. With only four months to go until perihelion – the closest point to the Sun – this process is well underway, with pronounced dust jets seen at all times on the comet’s day side. The two images released today show the remarkable onset of such a jet for the first time. They were taken on 12 March from a distance of 75 kilometres. In the first image, obtained at 07:13 CET, several rays of dust jets frame the upper, illuminated side of the comet. The dark underside shows no such features. Two minutes later, the picture has changed: a spectacular new jet has emerged on the dark side, hurtling dust into space and displaying a clearly discernable fine structure. “This was a chance discovery,” says OSIRIS principal investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. “No one has ever witnessed the wake-up of a dust jet before. It is impossible to […]

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