NASA/JPL/Arizona State University

WATER MARK. TES spotted geological signs of water in Meridiani in the form of a layer rich in hematite. Colors show hematite percentages in the surface materials range from 5 percent (aqua) to 25 percent (red). Mars rover Opportunity landed in the black oval and found rocks that had once been soaked in water.

Hunting Mars Minerals From Orbit
Scientists at Arizona State University's Mars Space Flight Facility designed the Thermal Emission Spectrometer (TES) instrument on NASA's Mars Global Surveyor orbiter and operated it until contact with the spacecraft was lost in November 2006. TES measured the thermal infrared energy (heat) emitted from Mars in many infrared "colors." This technique, called thermal emission spectroscopy, can tell us much about the geology and atmosphere of Mars.

In particular, TES identified an area in Mars' Meridiani Planum that contains a large exposure of the iron-oxide mineral hematite. Because hematite usually forms in association with water, NASA used the TES finding to pick Meridiani as the landing site for the Mars Exploration Rover Opportunity.

"Finding that hematite deposit was one of the shining achievements of TES," says principal investigator Phil Christensen of ASU. "As far as I was concerned, finding hematite accomplished TES' mission."