Alice returns results

Alice, the miniature ultra-violet imaging spectrograph aboard the Rosetta orbiter, has successfully relayed its first science data from Comet 67P/Churyumov-Gerasimenko – it’s darker than expected. NASA’s Alice has been mapping the far-ultraviolet light spectra of the comet’s surface since its rendezvous in early August, revealing the comet is unusually dark – darker than charcoal black – when viewed at ultraviolet wavelengths. The detector looks for thermal markers – noble gases – in the UV range to help determine the history of the comet. They can tell scientists where it was formed and where it has travelled. Alice is also ideal for visualising water and carbon monoxide and dioxide, which are formed in the coma, and has so far detected both hydrogen and oxygen. The surface has not revealed any water or ice patches, whichthe NASA team had expected to see because of the comet’s vast distance from the Sun. “We’re a bit surprised at just how unreflective the comet’s surface is and how little evidence of exposed water-ice it shows,” said Alan Stern, Alice principal investigator at the Southwest Research Institute in Boulder, Colorado where Alice was born. “As the mission progresses, we will continue to search for surface ice patches and ultraviolet colour and composition variations across the surface of the comet,” said Dr Lori Feaga, Alice co-investigator at the University of Maryland. Alice is designed to gather sensitive, high-resolution insight into the origin, composition and workings of the comet which are impossible to make from Earth. It is one of two full instruments on board Rosetta funded by NASA. The other is MIRO – Microwave Instrument for Rosetta Orbiter – which is designed to provide data on how gas and dust leave the surface of the nucleus to form the coma and tail. Rosetta aims to land a probe, Philae, onto the comet’s surface in November. The landing site - announced today - will be at the head of the comet at site J, with site C acting as a back-up. “As we have seen from recent close-up images, the comet is a beautiful but dramatic world – it is scientifically exciting, but its shape makes it operationally challenging,” says Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center. “None of the candidate landing sites met all of the operational criteria at the 100% level, but Site J is clearly the best solution.” It is hoped the mission will help scientists learn more about the origin and evolution of the solar system and the role comets might have played with serving Earth with water, and maybe even life.