NASA announced that one of its three instruments aboard Rosetta, the European Space Agency (ESA) spacecraft currently orbiting comet 67P/Churyumov-Gerasimenko, has successfully delivered its first set of science results back to Earth. Alice, an ultraviolet spectrometer, has revealed yet more unexpected findings about the comet, which Rosetta rendezvoused with in early August after a decade-long journey.
NASA revealed that Alice has shown the comet to be “unusually dark”—described as “darker than charcoal-black”—in ultraviolet light wavelengths. The instrument also revealed that the comet’s tail, or “coma,” contains hydrogen and oxygen, and the comet possesses no visible large ice patches. The latter finding is surprising, given the comet is quite some distance away from the Sun; patches of ice were expected to be found un-melted. Alan Stern, who is the Alice principal investigator at the Southwest Research Institute in Boulder, Colo., discussed these findings, underscoring their unanticipated nature.
“We’re a bit surprised at just how un-reflective the comet’s surface is, and how little evidence of exposed water-ice it shows,” Stern related.
Alice is one of two instruments aboard Rosetta fully funded by the United States’ space agency, and is meant to analyze the comet’s composition in a manner not possible from Earth or remote sites. According to a previous AmericaSpace article published in June, other instruments provided by NASA aboard Rosetta include the Microwave Instrument for Rosetta (MIRO) and the Ion and Electron Sensor (IES). The article stated that MIRO “will provide data about the evolution of the comet’s tail and ‘coma’ (the area around the comet’s nucleus), shedding light upon how this section of the comet develops as it approaches and departs our nearest star, the Sun.”
According to NASA, IES “is part of a suite of five instruments to analyze the plasma environment of the comet, particularly the coma.” NASA also helped to design a part of the Double Focusing Mass Spectrometer (DFMS) electronics package for the Rosetta Orbiter Spectrometer for Ion Neutral Analysis (ROSINA), which was mainly fabricated in Switzerland. In total, Rosetta carries 11 science instruments, as well as a lander, Philae.
While scientists marvel over data returned from Alice, at present time Rosetta’s team in Europe are hard at work determining possible landing sites for Philae, which is due to touch down on 67P/Churyumov-Gerasimenko in November. This occasion will mark the first ever cometary landing. In late August, ESA announced it had narrowed the pool of possible landing sites to five regions. Within the next few weeks, ESA will announce the ultimate landing site, with a “Go/No-Go” full assessment from Europe’s space agency and the lander’s team to be announced on Oct. 14.
This latest data from Alice caps off what has been an incredible year for the spacecraft, which faced a decade-long, 6.4-billion-kilometer transit following its early 2004 launch aboard an Ariane 5 launch vehicle from French Guiana’s Kourou Space Centre. In January, Rosetta was “woken up” from a marathon 31-month-long hibernation period; despite its long sleep, the spacecraft and its lander was found to be in excellent condition. During its approach to its cometary target, Rosetta uncovered many previous “unknowns,” including a unique double-lobed shape, an unexpected lack of ice, and excessive water outgassing.
On Aug. 6, scientists, researchers, and space buffs alike thrilled to the high-resolution images returned by the spacecraft, which had successfully rendezvoused with 67P/Churyumov-Gerasimenko that day, showing the comet and its distinctive features in unprecedented detail. In November, Rosetta will continue to bring thrills to the space and scientific communities, as Philae gets ready to make its historic “footsteps” on the comet. Rosetta and Philae will continue their science missions through December 2015, undoubtedly providing scientists with years of data from their historic “meet-up” with 67P/Churyumov-Gerasimenko.