This video has been made from a series of stills taken by Curiosity every few seconds. The stills were taken approximately every second or so, judging from the fact that the shadows and the sun do not move. If you look at this in full screen mode, you will see one object rise from the surface on the horizon, and another one cross the entire horizon from left to right. It isn’t clear what these objects are. Contrary to some of the commentary (it is exceptionally stupid, even for YouTube), the objects are not part of the Curiosity mission’s hardware. In addition, this low resolution camera would not be able to pick up an orbiting satellite from the ground. The object that crosses the horizon must be in the atmosphere, moving rather slowly in relation to the camera, and either very large or close enough for the camera to record it.
This is an interesting and unusual video. It is not presently explained.