HR: 0800h
AN: P21A-0135    [Abstracts]
TI: New Rock Physical Properties Assessments From the Mars Exploration Rover Rock Abrasion Tool (RAT).
AU: * Bartlett, P W
EM: Bartlett@HoneybeeRobotics.com
AF: Honeybee Robotics, 460 W34th Street, New York, NY 10001 United States
AU: Basso, B
EM: Basso@HoneybeeRobotics.com
AF: Honeybee Robotics, 460 W34th Street, New York, NY 10001 United States
AU: Kusack, A
EM: Kusack@HoneybeeRobotics.com
AF: Honeybee Robotics, 460 W34th Street, New York, NY 10001 United States
AU: Wilson, J
EM: Wilson@HoneybeeRobotics.com
AF: Honeybee Robotics, 460 W34th Street, New York, NY 10001 United States
AU: Zacny, K
EM: Zacny@HoneybeeRobotics.com
AF: Honeybee Robotics, 460 W34th Street, New York, NY 10001 United States
AB: The Rock Abrasion Tool (RAT) serves as the sample preparation device on the Mars Exploration Rovers (MER) science payload. The RAT grinds a circular area 45 millimeter in diameter, and on the order of a few millimeters deep, into a rock face. This process removes surface fines and weathered layers in preparation for imaging and spectral observations of the rock. As of September 2005, 15 grinding operations have been performed at Gusev Crater and 26 at Meridiani Planum. Since the RAT performs a mechanical operation on a rock, deductions can be made via the RAT's engineering data about the rock's physical properties. For each grinding operation, the energy consumed while grinding is converted to provide a physically relevant Specific Grind Energy (SGE) in terms of Joules per cubic millimeter of rock removed. The calculation is performed over the last 0.25 millimeter of a grinding operation, where it is possible, by taking measurements from Microscopic Imager images of the abraded area, to make an accurate estimate of the volume of rock removed. Progress is presented on recent refinement of the SGE calculation methods including decoupling of artifacts. Environmental factors and differing parameters used to command the RAT operations are among the key artifacts recently analyzed. Progress is also presented on further characterization of the dynamics and wear mechanics involved in the grinding process, and how they influence SGE. A library of Earth rocks has been assembled and it is being used with the RAT Engineering Model to create a set of similar SGE data products that can be compared to Mars rocks in order to contribute to physical properties assessments of the Mars rocks. Initial results indicate that the Martian rocks are analogous to a range of Earth rocks, from gypsum to low-strength basalt in terms of grindability; however, caution needs to be exercised in making a direct comparison of grinding energies. This is because the grindability of rocks was found to be a function not only of rock properties (such as the degree of weathering, mineral composition, and grain sizes) but also of the environmental conditions and other factors. Nevertheless, the SGE deduced from the RAT engineering data, and linked with data from other instruments in the payload, represent the most comprehensive database yet created of the physical properties of Martian rocks and are therefore of great value to our understanding of the geologic history of Mars and future instrument design for forthcoming Mars missions.
DE: 5194 Instruments and techniques
DE: 5415 Erosion and weathering
DE: 5460 Physical properties of materials
DE: 5494 Instruments and techniques
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005