Science Instruments

In the infrared spectrum, the instrument uses nine spectral bands to help detect minerals within the Martian terrain. These spectral bands, similar to ranges of colors, can obtain the signatures (spectral "fingerprints") of particular types of geological materials. Minerals, such as carbonates, silicates, hydroxides, sulfates, hydrothermal silica, oxides and phosphates, all show up as different colors in the infrared spectrum. This multi-spectral method allows researchers to detect in particular the presence of minerals that form in water and to understand those minerals in their proper geological context. THEMIS' infrared capabilities have significantly improved the data from TES (Thermal Emission Spectrometer), a similar instrument on Mars Global Surveyor.

The instrument's multi-spectral approach also provides data on localized deposits associated with hydrothermal and subsurface water and enables 328-foot (100-meter) images of Martian terrain to be captured in each pixel, or single point, of every image.

Variations in the thermal infrared "color" in the right-hand image are due to differences in the kinds of minerals that make up rocks and soil. In the visible part of the spectrum that our eyes can see (left-hand image), it would not be apparent what minerals are present.

ASTER, an Earth-orbiting instrument on the Terra spacecraft, has used a similar approach to map the distribution of minerals here on Earth.

The part of the imaging system that takes pictures in visible light is able to show objects about as big as a semi-truck. This resolution helps fill in the gap between large-scale geological images from the Viking orbiters in the 1970s and the very high-resolution images from Mars Global Surveyor.

When exposed to cosmic rays (charged particles in space that come from the stars, including our Sun), chemical elements in soils and rocks emit uniquely identifiable signatures of energy in the form of gamma rays. The gamma ray spectrometer looks at these signatures, or energies, coming from the elements present in the Martian soil. By measuring gamma rays coming from the Martian surface, it is possible to calculate how abundant various elements are and how they are distributed around the planet's surface.

Gamma rays, emitted from the nuclei of atoms, show up as sharp emission lines on the instrument's spectrum. While the energy represented in these emissions determines which elements are present, the intensity of the spectrum reveals the element's concentrations. The spectrometer has added significantly to the growing understanding of the origin and evolution of Mars and the processes shaping it today and in the past.

By measuring neutrons, it is possible to calculate the abundance of hydrogen on Mars, thus inferring the presence of water. The neutron detectors are sensitive to concentrations of hydrogen in the upper meter of the surface. Like a virtual shovel "digging into" the surface, the spectrometer allows scientists to peer into this shallow subsurface of Mars and measures the amount of hydrogen that exists there. Since hydrogen is most likely present in the form of water ice, the spectrometer is able to measure directly the amount of permanent ground ice and how it changes with the seasons.

Mars exploration space radiation comes from cosmic rays emitted by our local star, the Sun, and from stars beyond our solar system as well. Space radiation can trigger cancer and cause damage to the central nervous system. Similar instruments were flown on the space shuttles and are also flown on the International Space Station (ISS), but before Odyssey none had ever flown outside of Earth's protective magnetosphere, which blocks much of this radiation from reaching the surface of our planet.

A spectrometer inside the instrument measured the energy from the radiation sources mentioned above.

The instrument, with a 68-degree field of view, collected data during Odyssey's cruise from Earth to Mars. It stored large amounts of data for downlink whenever possible, and operated in orbit around Mars until a large solar event bombarded the Odyssey spacecraft on Oct. 28, 2003. MARIE has been unable to collect data since that time, and engineers believe the most likely cause is that a computer chip was damaged by a solar particle smashing into the MARIE computer board.