A field of barchan sand dunes appear turquoise blue on the surface of Mars in this enhanced image taken by the Mars Reconnaissance Orbiter. NASA/JPL-Caltech/University of Arizona
Two geologically young craters on the surface of Mars. NASA/JPL-Caltech/University of Arizona
Cliffs of ancient ice on the surface of Mars, featuring brown dusty cliff walls and light blue ice. NASA/JPL-Caltech/University of Arizona
Dunes on Mars are almost free of their seasonal ice cover during early Martian summer, with pockets of ice still visible in areas protected by shade, as seen in this Mars Reconnaissance Orbiter image. NASA/JPL-Caltech/University of Arizona
The surface of Mars after a meteoroid hit and exploded, creating an impact crater 5 meters across that triggered a one-kilometer-long slope streak, or avalanche. Image taken by NASA's Mars Reconnaissance Orbiter.
A view of the Ophir Chasma on the northern portion of the vast Mars canyon system, Vallles Marineris, taken by NASA's Mars Reconnaissance Orbiter. REUTERS/NASA/JPL/University of Arizona
Nili Patera, one of the most active dune fields on the planet Mars. Image taken by NASA's Mars Reconnaissance Orbiter. REUTERS/NASA/JPL-Caltech/Univ. of Arizona
Rough spherical features in an area called Yellowknife Bay. These features are interpreted as concretions, implying they formed in water that percolated through pores in the sediment.
An impact crater on Mars is seen in an image taken by NASA's Mars Reconnaissance Orbiter. REUTERS/NASA/JPL-Caltech/Univ. of Arizona
A rock outcrop called Link pops out from a Martian surface. Rounded gravel fragments, or clasts, up to a couple inches in size are in a matrix of white material.
The northern-most sand dunes are seen as they begin to emerge from their winter cover of seasonal carbon dioxide (dry) ice. REUTERS/NASA/JPL-Caltech/Univ. of Arizona
A location on Mars associated with the best-selling novel and Hollywood movie, "The Martian" This area is in the Acidalia Planitia region and in the novel and the movie, it is the landing site of a crewed mission named Ares
Portions of the Martian surface showing many channels from 1 meter to 10 meters wide on a scarp in the Hellas impact basin. REUTERS/NASA/JPL-Caltech/Univ. of Arizona
A view of the Noctis Labyrinthus region of Mars, perched high on the Tharsis rise in the upper reaches of the Valles Marineris canyon system. EUTERS/NASA/JPL/University of Arizona
The surface of the planet Mars inside Gale Crater seen from Curiosity. REUTERS/NASA
Curiosity appears as a bluish dot near the lower right corner of this enhanced-color view from Orbiter. REUTERS/NASA/JPL-Caltech/Univ. of Arizona
A gully in the sand dunes of Matara Crater on the surface of Mars, carved by seasonal dry ice that accumulates each year. NASA/JPL-Caltech/University of Arizona
Part of the wall of Gale Crater. Here, a network of valleys believed to have formed by water erosion enters Gale Crater from the outside. REUTERS/NASA/JPL-Caltech/MSSS
Two trenches dug by Phoenix's Robotic Arm. REUTERS/NASA/JPL-Caltech/University of Arizona
Mars' Victoria Crater at Meridiani Planum. REUTERS/NASA/JPL/Caltech
An iron meteorite on Mars in an image taken by the Mars Exploration Rover Opportunity. REUTERS/NASA/JPL/Cornell
This image, cropped from a larger panoramic image mosaic taken by the Mars Exploration Rover Spirit panoramic camera shows the rover's destination toward the hills nicknamed the Columbia Hills. REUTERS/NASA/JPLCornell