Writing about this in the Planetary Society Blog, Emily Lakdawalla notes that this is actually a strange anniversary to celebrate for MGS. Tenth anniversary, meaning ten complete orbits of the Earth, while MGS orbits a certain other planet. As an aside, she links to this page, explaining the Martian calendar, such as it is.
Solar longitude, eh? Nicely heliocentric. Time to bring our own calendar into the post-Copernican age perhaps?
Here's an image taken by Mars Global Surveyor (of Mars, funnily enough). Visible are Valles Marineris (the ruddy great big canyon) and Olympus Mons (the ruddy great big mountain).