NASA has three rovers on Mars right now: the twins Opportunity and Spirit, and the Sojourner. Of those three, only Opportunity is operational and is set to be joined by Curiosity on Sunday night.
In honor of the impeding the NASA Marshall Space Flight Center has been releasing photos on their official . The above photo was taken by the MRO Mars High Resolution Imaging Science Experiment spacecraft in orbit. The arrow points to Opportunity perched on the crater's edge.
Opportunity also took this panoramic shot back in 2008.

is expected to touchdown by 11:30 p.m. MDT and to start at 9:30 p.m. NASA will be streaming the mission coverage of Curiosity's landing on Mars live via NASA TV. You can either stream the feed or .
When I land on Mars, it'll be 5:31 UTC Aug. 6. See this handy chart for conversion to your time zone:
— Curiosity Rover (@MarsCuriosity)
Or you can always follow the .