Image Date - unknown (may be in 2015 )
Image Scientific Code Address - NASA's Spirit Rover - Rear Hazcam :: Sol 2169
First Image Source - http://mars.jpl.nasa.gov/mer/gallery/all/2/r/2169/2R318929995EFFB27MP1314R0M1.JPG
Second Image Source - http://mars.jpl.nasa.gov/mer/gallery/all/2/r/2169/2R318929995EFFB27MP1314L0M1.JPG
Nasa hides many other related Images to this. Only Two Images are available in Sol 2169 now. Those two photos show us a saucer like shape near Spirit Rover. NASA did not explain anything about it. But this UFO appears clearly here.
This UFO may be an Alien Spacecraft with beautiful lights and design and has been observing Spirit Rover's experiments.