Rosetta Spacecraft Recorded Landslide Occurring at Aswan Cliff on Comet 67P/ Churyumov–Gerasimenko

For the first time, astronomers have provided details of a landslide that occurred on Comet 67P/Churyumov–Gerasimenko and was captured by Rosetta spacecraft.

The images captured by the spacecraft, before and after landslide, revealed how a 100 meter-long Aswan cliff on the comet collapsed dramatically, creating a 70 m x 1 m fracture at the edge of the cliff. This image was captured by the spacecraft in September 2014. A separate camera on Rosseta captured another image on 10 July 2015, recorded a large plume of dust at the same region of the comet.

“The Rosetta mission observed several outbursts from its target comet 67P/Churyumov–Gerasimenko, which were attributed to dust generated by the crumbling of materials from collapsing cliffs. However, none of the aforementioned works included definitive evidence that landslides occur on comets. Amongst the many features observed by Rosetta on the nucleus of the comet, one peculiar fracture, 70 m long and 1 m wide, was identified on images obtained in September 2014 at the edge of a cliff named Aswan. On 10 July 2015, the Rosetta Navigation Camera captured a large plume of dust that could be traced back to an area encompassing the Aswan escarpment. Five days later, the OSIRIS camera observed a fresh, sharp and bright edge on the Aswan cliff,” the authors write in their study.

According to astronomers, the landslide can be linked to a cometary outburst occurring simultaneously in the same location. They suggest that when comets come near the sun, the plumes of gas and dust are typically seen and these are caused by crumbling and shifting of structures (cliffs or mounds) on the surface of the comet.

Earlier, researchers speculated that such outbursts were caused due to the blasts of pressurized gas building up in the comet’s interior as it warms.

“We report the first unambiguous link between an outburst and a cliff collapse on a comet. We establish a new dust-plume formation mechanism that does not necessarily require the breakup of pressurized crust or the presence of supervolatile material, as suggested by previous studies,” the authors say.

The Aswan cliff is located around the “wing” area of the duck-shaped comet 67P.

Researchers also simulated conditions at the surface of 67P at the time of the event, and concluded that temperatures at the Aswan cliff site in July 2015 would have increased from minus (–) 143 degree C to around 46 degree C in just 20 minutes because of the surface coming out of shadow into direct sunlight, thus illuminating the cliff for 90 minutes every 12 hours. This would have created intense temperature gradients, thus accelerating the emergence of fractures on the surface.

The detailed findings of the study have been published in the journal Nature Astronomy.