The Rosetta space probe has made a new discovery regarding the water-ice cycle of comet 67P/Churmov-Gerasimenko. As it turns out, the surface ice of the comet and its outgassing activities follow a cycle based on the sun’s illumination on the object, and it is theorized that this very cycle may be used by other comets.
Maria Cristina de Sanctis, part of INAF-IAPS (Institute of Astrophysiology and Spacial Planetology at the National Institute of Astrophysics in Rome), reveals that the probe, owned by the European Space Agency, observed a process that replenishes the surface of the comet with fresh ice with every new rotation. This helps to keep the comet alive in a sense. Comets (for those who don’t know) are formations of the solar system made up of dust, rocks, and ice; they are scattered around the sun and move in their own orbits.
THE “DAY AND NIGHT” CYCLE OF COMET 67P
Using Rosetta’s Visible Infrared and Thermal Imaging Spectrometer (VIRTIS), researchers have found a one square km region of Comet 67P’s neck where this process occurs, in which the water-ice on its surface dissipates and reappears in relation to its rotational position.
How does this happen? Well, when a comet nears the sun, the heat of the giant star vaporizes its icy surface into gas in a process known as outgassing. As the ice starts to sublimate, dust and rock in the comet is released and floats away from the comet’s surface, giving the celestial body its signature halo and tail.
By contrast, when the same area is not under sunlight, the surface cools until it re-freezes and the comet is re-covered with a very thin layer of ice. The process, driven by the day/night cycle, restarts when sunlight once again glides over the comet.
“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,” states 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.”
The findings of this study are now published in the journal Nature.
