Red Rover Goes to Mars

Science Instruments: A Geology Toolkit
Like a human field geologist, each Mars Exploration Rover has the capabilities to scout its surroundings for interesting rocks and soils, to move to those targets and to examine their composition and structure.
Spirit and Opportunity have identical suites of five scientific instruments: a panoramic camera provided by JPL; a miniature thermal emission spectrometer from Arizona State University, Tempe; a Moessbauer spectrometer from the Johannes Gutenberg University, Mainz, Germany; an alpha particle X-ray spectrometer from Max Planck Institute for Chemistry, also in Mainz, Germany; and a micro- scopic imager from JPL. These are augmented by a rock abrasion tool from Honeybee Robotics, New York, N.Y., for removing the weathered surfaces of rocks to expose fresh interiors for examination. The payload also includes magnetic targets provided by Niels Bohr Institute in Copenhagen, Denmark, to catch samples of martian dust for examination. The spectrometers, microscopic imager and abrasion tool share a turret at the end of a robotic arm provided by Alliance Spacesystems Inc., Pasadena, Calif.

_ Panoramic Camera ¡X Providing the geologic context: This high-resolution stereo camera reveals the surrounding terrain at each new location that the rover reaches. Its two eyes sit 30 centimeters (12 inches) apart, atop a mast about 1.5 meters (5 feet) above the ground. The instrument carries 14 different types of filters, allowing not only full-color images but also spectral analysis of minerals and the atmosphere. Its images are used to help select rock and soil targets for more intensive study and to pick new regions for the rover to explore.
_ Miniature Thermal Emission Spectrometer
¡X Identifying minerals at the site: This instrument views the surrounding scene in infrared wavelengths, determining types and amounts of many different kinds of minerals. A particular goal is to search for distinctive minerals that are formed by the action of water. The spectrometer scans to build up an image. Data from it and from the panoramic camera are used in choosing science targets and new areas to explore. Scientists also use it in studies of Mars¡¦ atmosphere.
_ Moessbauer Spectrometer ¡X Identifying iron-bearing minerals: Mounted on the rover arm, this instrument is placed against rock and soil targets. It identifies minerals that contain iron, which helps scientists evaluate what role water played in the formation of the targets and discern the extent to which rocks have been weathered. The instrument uses two cobalt-57 sources, each about the size of a pencil eraser, in calibrating its measurements. It is a miniaturized version of spectrometers used by geologists to study rocks and soils on Earth.
_ Alpha Particle X-Ray Spectrometer ¡X Determining the composition of rocks: An improved version of an instrument used by the Sojourner rover, this spectrometer is also similar to instruments used in geology labs on Earth. It uses small amounts of curium-244 in measuring the concentrations of most major elements in rocks and soil. Learning the elemental ingredients in rocks and soils helps scientists understand the samples¡¦ origins and how they have been altered over time.
_ Microscopic Imager ¡X Looking at fine-scale features: The fine-scale appearance of rocks and soils can provide essential clues to how those rocks and soils were formed. For instance, the size and angularity of grains in water-lain sediments can reveal how they were transported and deposited. This imager provides the close-up data needed for such studies.
_ Supplemental Instruments ¡X Engineering tools aid science: Each rover also has other tools that, while primarily designed for engineering use in the operation of the rover, can also provide geological information. The navigation camera is a wider-angle stereo instrument on the same mast as the panoramic camera. Hazard-avoidance cameras ride low on the front and rear of the rover in stereo pairs to produce three-dimensional information about the nearby terrain. The front pair provides information to aid positioning of the tools mounted on the rover¡¦s arm. Rover wheels, in addition to allowing mobility, are used to dig shallow trenches to evaluate soil properties.

Names of Rovers and Features
The names of the rovers, Spirit and Opportunity, were selected in a student essay contest that drew nearly 10,000 entries. After the spacecraft reached Mars, NASA dedicated the landers as memorials to astronauts who perished in space shuttle accidents. Spirit¡¦s lander became Columbia Memorial Station. Opportunity¡¦s became Challenger Memorial Station.
A committee of the International Astronomical Union designates official place names on Mars, such as the names Gusev Crater and Meridiani Planum. NASA and members of the rover science team have put unofficial names on many natural features seen by the rovers.
A range of hills that Spirit saw on the eastern horizon from the rover¡¦s landing site is unofficially called the ¡§Columbia Hills,¡¨ with seven individual hilltops named for members of the Space Shuttle Columbia¡¦s last crew: Anderson, Brown, Chawla, Clark, Husband, McCool and Ramon. Spirit drove more than three kilometers (about two miles) to reach those hills and begin climbing them.

As in earlier Mars surface missions ¡X Viking and Pathfinder ¡X scientists assign informal names to smaller features, such as rocks and patches of soil in order to avoid confusion when talking about plans and results related to those features. The named features range from stadium-size craters to coin-size spectrometer targets on rocks.