Monday, October 26, 2015

Evidence of the removal of slabs on 67P due to the forces at play during stretch

Many large flat bottomed "craters" are evident on 67P. For following reasons, these are hypothesised to be slabs of crust levered off the nucleus. When looking at the position of the fracture line and the shapes of the "craters" the best fit explanation is that the crust was brittle (fracture line is evident) and the interior is ductile (enabling stretch rather than complete fragmentation). The intense mass wasting that is modelled with a rigid model (citation needed here) is evidenced for the brittle crust and the fracture of the head lobe away from the body, but not for the interior.

To visualise how the missing slabs would fit back on to the pre-stretched comet, the following drawing was made which involves just cutting out the neck, fitting the head back on at the shear line, and placing slabs back where there was evidence they have come from. Also shown is a Navcam image where the craters are evident as missing slabs. Drawing by A.Cooper. Image courtesy of ESA Navcam - All annotations by A.Cooper.

Several "missing slabs" have had their own blog post detailing evidence of how they came to be including.

The amphitheatre slab A.
Slab B Babi

 Photo credits: Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO