- Questo evento è passato.
colloquium – Sonia Fornasier: Latest results on 67P/Churyumov-Gerasimenko comet from the OSIRIS instrument onboard the ROSETTA mission
Marzo 21 @ 11:30 - 12:30
The Rosetta space mission of the European Space Agency Rosetta has observed comet 67P/Churyumov-Gerasimenko for about 2 years, delivering the lander Philae on the comet surface for the first time in the history of the space exploration. Ended in September 2016, the Rosetta/Philae mission, acquired an incredible amount of unique data of comet 67P, allowing the most detailed study ever attempted of a comet.
Rosetta had a large complement of scientific experiments including the OSIRIS imaging system which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). More than 80000 images were acquired with the OSIRIS imaging system with spatial resolution ranging from several meters to a few centimeters per pixel during Rosetta’s descent to the comet in late September 2016. In particular, the high dynamics of the cameras detectors permitted to distinguish morphological structures on shadowed areas as well as frost layers, and to monitor at the same time the very dark surface, faint jets (with lifetimes shorter than a few minutes), and ices exposures.
An extensive catalogue of volatiles exposure was recently created permitting to investigate the link between composition, morphology and activity. It also indicates that ices exposures are typically sub-meter sized, information which is relevant for cometary models.
Detailed analysis of highly active regions revealed that the small lobe has different physical and mechanical properties than the big one and a lower volatile content, at least in its uppermost layers. These findings support the hypothesis that comet 67P originated from the merging of two distinct bodies in the early Solar System, as previously suggested by the geomorphological analyses of the comet terrains.
Finally, the reconstructed Philae orbit revealed that it had a second landing site located only 30 m apart from the final one. Philae stamped within a boulder for 25 cm depth, indicating that the cometary material is extremely soft and highly porous. This collision exposed the primordial water ice embedded within the boulder, providing an accurate measurement of the refractory to volatile ratio in comet 67P.