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More results from this week’s 50th Lunar and Planetary Science Conference in Texas! Two presentations today focused on showing the dramatic changes on the surface of Comet 67P/C-G that were documented by Rosetta. The first focused on the changes produced after massive outbursts during the comet’s closest approach to the Sun. The second documented several more evolutionary changes that changed more slowly.
The image to the right comes from the first paper, and shows the changes that took place on the surface following one massive outburst, with the numbers in red indicating unchanged features between the two photographs.
It appears an entire cliff section has disappeared, replaced by a single large giant boulder. Interestingly there is no obvious vent opening for the outburst. Instead, it appears that the eruption occurred below ground, and merely blasted part of the surface into space. As noted in the paper:
We report here on a third cliff collapse that occurred in the southern hemisphere in the Sobek region , which corresponds to the neck region in the 67P’s southern hemisphere. Due to the close alignment of the 67P’s
southern summer solstice with perihelion passage, the southern hemisphere is subjected to higher solar input, resulting in higher levels of activity and more intensive erosion. The location of the collapsing cliff in Sobek is consistent with the inferred source region of one of the strong outbursts [previously reported].
The paper also showed evidence of a large boulder more than a 100 feet across moving several hundred feet over a period of seven months.
The second paper showed various changes in a number of depressions and scarps on the smooth flat surfaces near the narrow neck that connected the comet’s two lobes. Examples of this terrain can be seen in high resolution pictures here and here and here and here.
From this data scientist suggest that the neck region is slowly dissolving away, its material in these flat areas flying away because the neck happens to be a region of low gravity.