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INAF: That’s how it has turned the surface of comet 67P.

Press release – The surveys obtained by OSIRIS, an instrument that sees a significant Italian contribution, whose channel large angle has been achieved by CISAS (University Centre of Studies and Activities for Space of the University of Padova) for ASI, Italian Space agency, and INAF, have allowed us to observe for the first time the changes in the structures on the surface of the nucleus of a comet during its perihelion passage and understand more precisely the mechanisms that shape the surface.

Slumping of rocky walls that lead to light large ice concentrations, boulders that roll on the valley floor to tens of meters. It ‘a surprising landscape and constantly changing one of the comet 67P core surface Churyumov-Gerasimenko, taken between 2014 and 2016 from the chamber to OSIRIS images (Optical, Spectroscopic, and Infrared Remote Imaging System) on board the Rosetta mission of ESA and which emerges from the results of two different articles published in the journals Science and Nature Astronomy. In the two international teams who conducted the investigation scientists from various Italian universities and research institutes they are involved.

The article published in Nature Astronomy, describes the ruinous detachment of a part of the rocky ridge material called Aswan and Seth located in the region of the 67P nucleus. On July 10 of 2015 more than 57 thousand cubic meters of material are precipitated in the downstream direction for about 150 meters, accompanied by a violent jet of dust and gas observed by the Navigation Chamber of Rosetta.

After five days, the filming of the area obtained from OSIRIS have not only confirmed the collapse but have highlighted that the event had exposed an inner area of the very bright nucleus: more than six times that of the surrounding area, very dark. Researchers believe very likely that the bright region exposed after the collapse is composed of ice.

The second article, published in the journal Science, has reviewed the transformations of the surface of comet 67P recorded by Rosetta mission since the summer of 2014 until its conclusion in September 2016, when the probe is permanently placed on the comet’s nucleus. The team highlighted the extreme geological dynamics of the comet, that in such a limited period of time showed the rocky flank collapses – as in the event of Aswan – or surface fractures that open up and expand, moving rocks that change position of tens of meters, but also rains of debris which cover certain areas of the surface. Incidents related to these phenomena that occur on the comet: those type of erosion, those related to rapid changes in temperature or related to the sublimation of the ice trapped inside the core, up to those due to mechanical stresses generated by the rapid rotation of the nucleus. The two scientific studies are the first to describe the surface changes observed by OSIRIS on 67P, which mainly concern the northern hemisphere, the only observed at good resolution on arrival and two years later. The biggest changes concern instead the southern hemisphere, which perihelion lost two meters of medium thickness – partially lost in space, in part transferred to the deposits of pebbles and boulders northern hemisphere – but that too has been observed from afar and however on too short periods to snatch the details. The observed changes suggest that most of the topography of the comet nucleus has been modeled before the 1959, namely on different orbits from the current.



To open the video click on the image, good view from your Alessandro Brizzi.