The Mini-Thermal Emission Spectrometer, or Mini-TES, is an instrument that sees infrared radiation emitted by objects. The instrument is located at the bottom of the rover's mast, and scanning mirrors reflect light down to it. It sees the terrain around the rover from the same vantage point as Pancam. The Mini-TES is similar to Mars Global Surveyor's Thermal Emission Spectrometer (TES) instrument. The Rover's Mini-TES determines from afar the mineral composition of martian surface features and select specific rocks and soils to investigate in detail. Making measurements in the thermal IR has many advantages. The thermal IR has the ability to penetrate through the dust coatings common to the martian surface that can present problems for remote sensing observations. At these wavelengths, Mini-TES can recognize carbonates, silicates, organic molecules, and minerals formed in water. Thermal IR data also helps scientists assess the capacity of rocks and soils to hold heat over the wide temperature range of a martian day.
Source: NASA, Cornell University