It does look somewhat like if a bunch of pebbles hit the car really hard, but the puzzling part is that the front of the car doesn't have any damage like this at all. In fact the other side or anywhere else on the car doesn't have any damage. Its only on the passenger side door and fender. Could it have been parked and a really big gust of wind slammed it with rocks and dust??

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2001 X5 4.4i
2002 Honda S2000