As both cams point to the same direction at the same time the images were taken within a split second from each other, in my opinion, we can rule out that it is an optical illusion, dust or spots on both lenses. What do you think?
Image shows position of the Cams
Objects Rear Hazcam: Right B 2014-12-12 03:16:20 UTC
Objects Rear Hazcam: Right B 2014-12-12 03:16:20 UTC
Objects Rear Hazcam: Left B 2014-12-12 03:16:20 UTC
SOL 835
Link to Image 1:
http://mars.jpl.nasa.gov/msl-raw-images/proj/msl/redops/ods/surface/sol/00835/opgs/edr/rcam/RRB_471625353EDR_F0442336RHAZ00311M_.JPG
Link to Image 2:
http://mars.jpl.nasa.gov/msl-raw-images/proj/msl/redops/ods/surface/sol/00835/opgs/edr/rcam/RLB_471625353EDR_F0442336RHAZ00311M_.JPG