Our mapping reveals strong latitudinal dependences for emplaced units and a highly heterogeneous surface. Our mapping describes the landscapes of 67P/C-G when they were first observed by Rosetta, and our map can be used to detect changes in surface morphologies after its perihelion passage. Relative to other nuclei, 67P/C-G appears most similar to 81P/Wild 2, with a topographically heterogeneous surface dominated by smooth-floored pits. Our work also puts into greater context the morphologies studied in previous works, and also the morphologies observed on previously visited cometary nuclei. Imagery of the southern hemisphere was included in our study, allowing us to compare the contrasting hemispheres of 67P/C-G in a single study. The images used in our study were acquired between August 2014 and May 2015, before 67P/C-G passed through perihelion. We present a global geomorphological map of comet 67P/Churyumov-Gerasimenko (67P/C-G) using data acquired by the Rosetta Orbiter’s OSIRIS Narrow Angle Camera. In our future study, we will model pinnacles formation based on the here presented analysis of observations. Suggesting that they have been formed by sublimational erosion, this value allows estimating the minimum thickness of the eroded material and thus the degree of the evolutionary changes of the nucleus. We found that the maximum height of the pinnacles is about a hundred meters. At the same time the mean values of the measured parameters, including the height, show no statistically reliable difference between the north and south. This difference possibly indicates the higher effectiveness of the pinnacles' formation in the southern hemisphere. In the southern hemisphere, number of both round pinnacles and local ridges is larger than in the northern hemisphere. About a third of them have planimetrically rounded shape (rounded pinnacles) and the rest are planimetrically elongated (local ridges). We mapped 166 pinnacles on the comet nucleus surface of 67P/Churyumov-Gerasimenko. Therefore, a study of the areal distribution of pinnacles on the nucleus surface and their morphology may help to understand the structure and properties of the nucleus material. However, the amount of solar radiation and the thermal gradient is different across the orbit for geomorphological regions, which can result in different erosion and shape for a similar composition among two differently illuminated areas. In the case of comets, areal changes in the degree of erosion could be related to inhomogeneities of the nucleus. Pinnacles are local topographic promontories of different shapes considered to be formed due to uneven surface erosion. The terrains on Borrelly suggest that solar energy input could map directly into erosional processes and landforms. ![]() ![]() Differences in energy input may produce different varieties of sublimation erosional landforms. Erosional rates across the comet are probably controlled by solar energy input and the location of the subsolar point during perihelion. The formation and the morphologies of units and features appear to be driven by differential rates of sublimation erosion. Because of the relatively short period of this comet, surface erosion by volatile sublimation is, in geologic terms, a very active process. In strong contrast to asteroids, unambiguous impact craters were not observed on Borrelly's surface. The features are named ridges, troughs, pits, and hills. The morphological units are named dark spots, mottled terrain, mesas, and smooth terrain. Based on analysis of the highest resolution images, stereo images, photometry, and albedo we have mapped four major morphological units and four terrain features. It transformed Borrelly from an astronomical object shrouded in coma of gas and dust into a geological object with complex surface processes and a rich history of erosion and landform evolution. The flyby of the nucleus of the Comet 19P/Borrelly by the Deep Space 1 spacecraft produced the best views to date of the surface of these interesting objects.
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