Rosetta presents a year-long investigation of the comet water cycle behavior to prove surprising and accurate results
European Space Agency’s Rosetta spacecraft, is one of the many tasked with observing and finding out as much as it can about space bodies. Rosetta was launched in August, 2014 towards currently orbiting comet 67P/Churyumov-Gerasimenko that was making its way towards the sun.
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During its observation, the probe stuck close to the neck of the comet. On August 13th, the comet got the closest to the sun. It was the closest it could get with its 6.5-year. Scientists used Rosetta’s Visible, InfraRed and Thermal Imaging Spectrometer, VIRTIS, have identified a region on the comet’s surface where water ice appears and disappears in sync with its rotation period.
Their findings are published today in the journal Nature. Planetary scientist Maria Cristina De Sanctis, from the Institute for Space Astrophysics and Planetology from INAF-IAPS in Rome, Italy and the lead author of the study, wrote in an email to Discovery News that they had found a mechanism that replenishes the surface of the comet with fresh ice at every rotation: this keeps the comet ‘alive’.
She elaborated that they saw the tell-tale signature of water ice in the spectra of the study region but only when certain portions were cast in shadow. Conversely, when the Sun was shining on these regions, the ice was gone. This indicates a cyclical behavior of water ice during each comet rotation.
“We found a mechanism that replenishes the surface of the comet with fresh ice at every rotation: this keeps the comet ‘alive’,” says Maria Cristina.
ESA Rosetta’s study presents a set of data taken in September 2014, concentrating on a one square km region on the comet’s neck. At the time, the comet was about 500 million km from the Sun and the neck was one of the most active areas. The scientists found out that as the comet rotates, taking just over 12 hours to complete a full revolution, the various regions undergo different illumination.
“We saw the tell-tale signature of water ice in the spectra of the study region but only when certain portions were cast in shadow,” says Maria Cristina. “Conversely, when the Sun was shining on these regions, the ice was gone. This indicates a cyclical behaviour of water ice during each comet rotation.”
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These finding are helpful in resolving the puzzle about why a comet’s surface can be relatively free of ice. These include questions such as what has been observed on 67P and other comets, even though the bodies are outgassing water. The cycle of condensation and sublimation shows how water ice can be transported from the interior of the comet to the surface.