Meridiani Planum

When NASA's Mars Exploration Rover, Opportunity, landed on Meridiani Planum in January 2004, it quickly found what it had been sent from Earth to find: evidence of liquid water in the Martian past.

This image shows a false-color view of part of Meridiani Planum, about 400 kilometers (250 miles) northeast of where Opportunity landed. The image was taken by the Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey orbiter. THEMIS is a camera that images Mars in 5 visible and 10 infrared "colors." The image combines daytime and nighttime infrared views. Reddish areas have more rocks and hardened sediments, while bluish areas feature more dust, sand, and fine-grain material.

Opportunity was targeted on Meridiani because remote sensing from orbit by another mission, NASA's Mars Global Surveyor, showed that portions of Meridiani contain up to 20 percent gray crystalline hematite at the surface. Hematite is an iron-oxide mineral, and on Earth the gray crystalline variety forms mostly in association with liquid water.

Image credit: NASA/JPL-Caltech/Arizona State University