Did NASA Cover Up Aliens Hiding Near Saturn?

Some are claiming NASA photoshoped a Cassini orbiter image of Saturn's moon Dione. The image can be seen clearly in the video embedded below. It does appear to be obviously altered, but why?
Alien conspiracy theorists are confident they've caught NASA in the act of covering up the fact that we are not alone in the universe.

A video posted on YouTube yesterday showed how an image of Saturn's moons Dione and Titan, taken by NASA's Cassini orbiter, had been digitally altered before being added to the space agency's Picture of the Day website.

In the video, "DominatorPS3" turned up the brightness levels on the photo to show that a "huge" object can be seen behind the smaller moon, Dione. Clearly visible are brush strokes that show how the rainbow aura of the object has been blacked out.