Dark Disk Observing NASA Rover On Photo Taken Dec 4, 2015, UFO Sighting News.

Date of sighting: December 5, 2015
Location of sighting: Mars
Camera: Rear Hazcam, Sol 1183, Dec 4, 2015, 16:14:46 UTC, left B

This is a UFO from the most recent photos from Curiosity rover this week. It has a dark disk and is not an anomaly stuck to the lens. I checked other photos from the same camera and it is not there, therefore its not on the lens. It is flying in a horizontal position and observing the rover from a distance. 
Scott C. Waring