Here's another thought:

It's interesting that this "object" should appear so close to the airbag retraction drag marks (as indicated by the darker splotches). Possibly as the airbag itself was retracting, part of a still-billowed out section had the "opportunity" to continously rub/abrade/polish against a protusion in the ground. The ring pattern does seem to my eye to be oriented somewhat in the retraction direction.

RBG