Seeing as how the other camera on the rover did not capture this "light" (as seen clearly in this GIF: http://i.imgur.com/LQa9PLU.gif) it seems pretty safe to assume that this is just an artifact caused by a temporary glitch on one of the cameras.
Here are the two source images taken at the same time by the rover's two cameras:
But of course disreputable "news" sites bring in a UFO enthusiast as their source for a quote about the possibility that there is intelligent life below the surface.
