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The southern hemisphere of comet 67P/Churyumov-Gerasimenko (67P) becameobservable by the Rosetta mission in March 2015, a few months before cometarysouthern vernal equinox. The Anhur region in the southern part of the comet'slarger lobe was found to be highly eroded, enriched in volatiles, and highlyactive. We analyze high-resolution images of the Anhur region pre- andpost-perihelion acquired by the OSIRIS imaging system on board the Rosettamission. The Narrow Angle Camera is particularly useful for studying theevolution in Anhur in terms of morphological changes and colorvariations.}{Radiance factor images processed by the OSIRIS pipeline werecoregistered, reprojected onto the 3D shape model of the comet, and correctedfor the illumination conditions. We find a number of morphological changes inthe Anhur region that are related to formation of new scarps; removal of dustcoatings; localized resurfacing in some areas, including bouldersdisplacements; and vanishing structures, which implies localized mass loss thatwe estimate to be higher than 50 million kg. The strongest changes took placein and nearby the Anhur canyon-like structure, where significant dust cover wasremoved, an entire structure vanished, and many boulders were rearranged. Allsuch changes are potentially associated with one of the most intense outburstsregistered by Rosetta during its observations, which occurred one day beforeperihelion passage. Moreover, in the niche at the foot of a new observed scarp,we also see evidence of water ice exposure that persisted for at least sixmonths. The abundance of water ice, evaluated from a linear mixing model, isrelatively high (> 20%). Our results confirm that the Anhur region isvolatile-rich and probably is the area on 67P with the most pristine exposuresnear perihelion.

Surface evolution of the Anhur region on comet 67P from high-resolution OSIRIS images