Article from the website theblackvault.com.
ExplainableOfficial NASA Caption: Microscopic Imager Non-linearized Full frame EDR acquired on Sol 654 of Opportunity's mission to Meridiani Planum at approximately at approximately 12:02:57 Mars local solar time, Microscopic Imager dust cover commanded to be CLOSED. NASA/JPL/Cornell/USGS
Original NASA Source: Opportunity - All Raw Images Sol 654 (60 images)
What are we looking at? In this photo, there is, what appears to be, an unknown object hovering in the background. It does not appear to be a rock or other object connected to the rover.
Click on this link to read more http://www.theblackvault.com/m/events/view/Unknown-Object-Caught-by-Mars-Exploration-Rover.