Geologic mapping of the Comet 67P/Churyumov-Gerasimenko's Northern Hemisphere

OSIRIS, the Scientific Imaging System onboard the Rosetta mission, has been acquiring images of the nucleus of the comet 67P/Churyumov-Gerasimenko since August 2014 with a resolution that allows a detailed analysis of its surface. Indeed, data reveal a complex surface morphology that is likely the expression of different processes that occurred at different times on the cometary nucleus. In order to characterize these different morphologies and better understand their distribution, we performed a geologic mapping of comet's 67P northern hemisphere in which features have been distinguished based on their morphological, textural and stratigraphic characteristics. For this purpose we used NAC images acquired on August and September 2014 with a spatial scale ranging from 1.2 to 2.4 m/pixel. Several different geologic units have been identified on the basis of their different surface textures, granulometry, and morphology. Some of these units are distinctive and localised, whereas others are more common and distributed all over the northern hemisphere. Moreover, different types of linear features have been distinguished on the basis of their morphology. Some of these lineaments have never been observed before on a comet and can offer important clues on the internal structures of the nucleus itself. The geologic mapping results presented here will allow us to better understand the processes that affected the nucleus’ surface and thus the origin and evolutionary history of comet 67P/Churyumov-Gerasimenko.