A Deposit on Mars Layered alunite-kaolinite deposit near Cross Crater on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment. Image and caption: NASA

A Tale of Two Craters Two craters at Noctis Labyrinthus on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment. Image and caption: NASA

Dust Devil Lines in the Sand Dust devil lines in the sands of Mars, seen by the MRO Mars High Resolution Imaging Science Experiment at Active Dune Gully. Image and caption: NASA

Gagarin Rock “Gagarin” Rock, seen by the panoramic camera of the MRO Mars High Resolution Imaging Science Experiment. Image and caption: NASA

Possible Cyclic Bedding Image of possible cyclic bedding on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment near Arabia Terra. Image and caption: NASA

Valleys Carved Into Elysium Mons Image of valleys carved into Elysium Mons on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment. Image and caption: NASA

Mars, Exposed! Image of exposed rock laters on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment in the Argyre Region. Image and caption: NASA

Shadows on Mars The shadow of the Mars Exploration Rover Opportunity rover, seen near Endeavor Crater on Mars. Image and caption: NASA

Landforms on Mars Landforms on the south polar residual cap on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment. Image and caption: NASA

Crater Water Ice on Mars Crater water ice on Mars at Vastitas Borealis, seen by the European Space Agency's Mars Express. Image: ESA, caption: NASA

Opportunity's Panoramic View of Mars A view of Mars from the southwest side of Victoria Crater, seen by the Mars Exploration Rover Opportunity. Image and caption: NASA

Hebes Chasma on Mars Hebes Chasma on Mars, northern side of Valles Marineris, seen by the Thermal Emission Imaging System. Image and caption: NASA

Dunes in Herschel Crater on Mars Dunes in Herschel Crater on Mars, seen by the HiRise instrument on the Mars Reconnaissance Orbiter (MRO). Image and caption: NASA

Opportunity on Mars Opportunity on the rim of the Santa Maria Crater, seen by the MRO Mars High Resolution Imaging Science Experiment spacecraft. Image and caption: NASA

Fading Rover Tracks on Mars Fading rover tracks on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment in 2009 near Victoria Crater. Image and caption: NASA

Sunset on Mars A sunset on Mars, seen by the the Mars Exploration Rover Spirit in 2005 at Gusev Crater Rim. Image and caption: NASA