Measurements taken by the European Space Agency’s Rosetta spacecraft, now orbiting comet 67P/Churyumov-Gerasimenko, show that ice builds up when a particular region of the comet is in shadow. This gas flows away from the comet, carrying dust particles along and building up the characteristic bright tail and halo.Rosetta reached Comet 67P/Churyumov-Gerasimenko in August 2014 and has been studying it up close for over a year. The researchers have actually recently identified a region on the comet’s surface where water ice appears and disappears in sync with its rotation period.
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“We observed this cycle for several comet rotations”, says planetary scientist Maria Cristina De Sanctis from the Institute for Space Astrophysics and Planetology in Rome.
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. If the water vapor is being stripped from the comet before it can freeze again, there must be another source of water on the comet that allows the ice sheet to replenish with each cycle.
Comets, of course, have a day-night cycle, just as Earth does and just as all bodies in our solar system do.
The scientists are now busy analyzing VIRTIS data collected in the following months as the comet’s activity increased around the closest approach to the Sunday.
ESA’s Rosetta spacecraft may reveal a bit more about how comets “stay alive” with their daily water-ice cycle.
Heat from sunlight kicks off the sublimation, where the ice goes directly from its frozen state to a vapor without an intermediate liquid stage.
Scientists have discovered an unexpectedly regular cycle of ice formation and depletion on the surface of a comet.
The ice was spotted in data gathered last August using Rosetta’s VIRTIS instrument – a spectrometer created to map the comet’s chemical composition. The daily exposure to sun also drives the outbursts of water.
Alternating sunlight and darkness at Comet 67P creates miniature weather fluctuations, researchers find.
“Rosetta is capable of tracking changes on the comet over short as well as longer time scales, and we are looking forward to combining all of this information to understand the evolution of this and other comets”. Down to a few cm deep over the region of the portion of the comet nucleus that was surveyed, water ice accounts for 10-15 per cent of the material and appears to be well-mixed with the other constituents.
Comets hurtling through our solar system may have their own water cycles according to the latest findings from the Rosetta space probe.
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The researchers say they suspect it is being replenished from beneath, from within the comet’s interior, as the extreme difference between sunlight and shadow temperatures cracks the surface, creating a path for water to rise from inside.
