Doing a quick search, I found that this had been mentioned once or twice, but now that we have the pictures in their full glory, I thought I would present them to all for your viewing pleasure: a 1909 VDB Lincoln Cent on the surface of Mars, a part of the camera calibration equipment of the NASA rover Curiosity.
Some plausible PCGS alibis: "We don't grade alien coins..." or "Your coin will be processed on July 17, 2018 following its release from quarantine..." or "We are returning your coin because it has an unknown reddish granular contaminant on the obverse..."
Before launch images show it to be newly cleaned it seems to be toning quickly. New term for Coins Talk AT* Alien Toned.