Optical Maturity Study of Planetary Regoliths
A NovaSol proposal entitled "Optical Maturity Study of Planetary Regoliths" has been selected for funding by the Planetary Geology and Geophysics program within the NASA Office of Space Science. The three-year program is for basic research on the remote sensing properties of the rocky soil, known as "regolith," covering the surface of the Moon. The project will examine how composition affects the optical characteristics of the regolith. The study will also focus on the process of "maturation," or the physical, chemical and optical changes that occur with time as the surface is exposed to the space environment. A class of unusual bright features called "lunar swirls" will be studied for the clues they can provide to the understanding of maturation. Competing hypotheses for the formation of the swirls include the impact of comets with the Moon and unusual magnetization of the rocks. The work conducted for this project may help to solve the mystery of the swirls' origin. Knowledge of these phenomena may lead to techniques for remote dating of meteorite impact craters on the Moon, and hence provide important information on the frequency of impacts on Earth.
Below is a false-color image of the nearside of the Moon. The image is a mosaic constructed from hundreds of thousands of individual multispectral frames returned by the Clementine spacecraft. The red-to-blue tones are related changes in composition. Redder areas are higher in iron content, bluer areas have less iron in the rocks. The deep red areas are the lunar maria, which appear dark when looking at the Moon with the eye. The maria are made of a volcanic rock called basalt, very similar to the rocks composing the Hawaiian islands. The green channel in the image displays a measure of the "maturity" of the surface. Younger material ejected from large impact craters is bright, while areas of older material have been darkened by long exposure to bombardment by micrometeorites, the solar wind, and cosmic rays.
False-color image of the nearside of the Moon.
Imaging and spectral data for the study come from spacecraft such as Clementine and Galileo, telescopes on Mauna Kea, and laboratory analysis of lunar samples returned by the Apollo astronauts. The results of the work will aid in the interpretation data from NASA's MESSENGER mission to the planet Mercury, scheduled for launch in 2004.
NovaSol principal scientist David Blewett leads the investigation, which includes collaborators from the Hawaii Institute of Geophysics and Planetology at University of Hawaii at Manoa, and Northwestern University. He holds a B.A. in Astrophysics from the University of Pennsylvania and an M.S. and Ph.D. in Geology and Geophysics from the University of Hawaii. Dr. Blewett has been involved in remote sensing and geologic study of the Moon for over 12 years. He also performs research for a fluorescence-based pathogen detection system, and contributes to NovaSol's Navy-funded effort to develop an automated target-detection system for airborne hyperspectral imagers.