Thats a transit of Deimos. For timing - each image is 10s apart - so it takes just over 2 minutes to complete the transit.

There was an eclipse season just after landing. If anyone had suggested that either rover would last till THIS eclipse season - they'd have been immediately sent to a secure mental institution. They just continue to amaze and astonish. For those that didnt know - Spirit's arthritic FR wheel has been back to nominal for a few months - both have had a recent flight software update - and both are at power levels comparable to the end of the Primary mission. Things havnt been this good for more than 10 months!

Doug