Comet Sinkholes

Is that a bunch of Corvettes I see down at the bottom of that large sinkhole?

that was a sad day for vette fans

It makes sense, the volatiles sublime leaving gaps. The gravity is very weak, so the dirt part of the dirty snowball would very slowly drop to the bottom of the hole.

I agree impacts are unlikely, however, since this is more likely rock, then we need a different cutting medium. In case you missed the true-colour image of C67 there were not many released - here is one which definitely looks more like Martian rock than dusty iceball! Obviously taking 3 sequential colour separation shots does not work too well on a fast rotating body, hence ESA kept to the monochrome ("icy-grey") views. Which also makes everyone think it's a grey snowball. Cr*p!

I'm of the camp that supports EDM cratering. We are a growing minority who realise that the universal nature of cratering across the solar system, makes mechanical 'impacts' less probable, particularly when you see the relative size of these holes. It's not difficult to run the experiment if you have a handy 10kV source. Interplanetary discharges in earlier times must have been on a prodigious scale, and plasma works very well as a cutting tool!