Distribution and Orientation of Wind-Tail-Like Morphologies on Comet 67P/Churyumov-Gerasimenko

Kurzfassung

High resolution image data of the ROLIS and OSIRIS instruments on-board the Rosetta spacecraft and its lander Philae revealed the presence of aeolian-like morphologies on the comet surface [e.g. 1, 2]. In particular, there is a set of elongated wind-tail like deposits and moat-like depressions around some larger boulders (> 5 m). Such features are commonly associated with wind accumulation and wind erosion on Earth and other planets. However, the formation mechanism of wind-tail-like features on Churyumov-Gerasimenko appears to be of different origin. It is probable that they form as a result of abrasion of a sand-bed of air-fall particles [1, 2, 3]. Assuming that the direction of the wind-tail-like features is associated with the direction of the air-fall in the area, we investigated boulders with wind-tail-like morphologies on pre-perihelion OSIRIS images of resolution better than 50 cm/pixel. We considered the entire sunlit surface of the comet and found that there are regions which show many wind-tail-like features, such as the area around Philae's first landing site Agilkia. Other areas, however, are depleted. Our aim is to track possible air-fall directions from the shape and direction of the wind-tail-like deposits and determine the source of the air-fall particles. We base our analysis on the method described by Mottola et al. [2], which assumes that the boulders were previously covered by fine particles which were subsequently removed by impinging air-fall particles. We will compare our observational results with existing models of dust transport on Churyumov-Gerasimenko [3]. References: [1] Thomas et al.,2015, A&A 583. [2] Mottola et al., 2015, Science 349. [3] Kramer and Noack, 2015, AJL 813.