[wymy]

If it pitted the glass lense, wouldn't the solid exhaust penetrate the plastic bag? I'm surprised there was no other damage.

[tritium]

I think it's about force and hardness, contrasted against elastic and inelastic collisions.

Either that, or maybe the caustic qualities have something to do with it? I'm not sure of the chemical aspects of the exhaust, but that part is also mentioned in conjunction with the debris accumulation.

[wutbrodo]

I don't think that follows. Sand can pit a lens, right. And yet sand with the same force wouldn't penetrate a plastic bag.