Date of sighting: December 5, 2015
Location of sighting: Mars
Source URL: http://mars.jpl.nasa.gov/msl-raw-images/proj/msl/redops/ods/surface/sol/01183/opgs/edr/rcam/RLB_502516568EDR_F0511430RHAZ00313M_.JPG
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