Are These Bubbles?

I just came across a 2008 quarter with strange markings on them. At first I thought they were pits, perhaps having spent some time in someone's driveway being driven on over and over again, but I would imagine there would be more severe scratches on the coin if that were the case.

The "pits" are very prominent on the reverse, with several on the obverse as well. Are they gas bubbles? Are they pits from some external material? or are they something else entirely?

On the obverse at 3 oclock there is some chipping and what appears to be rust in that spot. There evidently is some damage from an external material to this coin, but considering the number of pits and on both sides, it doesn't seem to add up to me.

I'd really appreciate someone teaching me something about this :)