Energy Minerals in near-Earth Asteroids
Asteroids represent the most accessible, resource-rich bodies in the Solar System. Primary energy minerals in these bodies are organic molecules ranging from low-weight molecular hydrocarbons to high-molecular weight kerogen-like material. In well-characterized carbonaceous chondrites such as Murchison, ~25% of organic matter is present as solvent-soluble or free compounds, which include aliphatic and aromatic hydrocarbons. The remaining 75% is a complex solvent-insoluble macromolecular material. Methane is present at the 20-30 ppm level in Murchison. In contrast, methane is below current detection limits in the Orgueil CI chondrite, another carbon-rich meteorite. Successful extraction of this potential resource requires strong synergy between ground-based observations and engineering solutions.
Asteroids are diverse bodies with a wide range of properties. Several hundred thousand asteroids have been discovered.Asteroids are characterized based on their spectral properties, primarily in the visible and infrared wavelength regions. Of primary interest for resource extraction are D-type and C-type asteroids. D-type asteroids are low-albedo objects (0.02-0.06) and have relatively featureless spectra with steep red slopes. C-type asteroids also have low albedos (0.03-0.10) with slight bluish to slight reddish slopes and absorptions blueward of 0.5 µm. Both D- and C-types are designated as “primitive carbonaceous asteroids” and are likely composed of organic-rich compounds and hydrated minerals. The connection between organic-rich meteorites and “primitive carbonaceous asteroids” is tenuous and requires advanced exploration to identify the resources of near-Earth space.
Target selection for resource extraction is limited by our poor understanding of the asteroid population. Ground-based surveys of the asteroid population focus on detection and orbit determination. Orbit determination is only the first step in resource assessment. A real need exists for extension of Asteroid Surveys to include physical characterization. The most effective ground-based characterization is done using radio telescopes. Radar data provides the shape and size of asteroid, evidence of craters, boulders and surface features, evidence of regolith, size distribution of regolith, and the presence of satellites, which allow for a mass determination. Only with such data in hand can effective reconnaissance missions be planned to identify energy minerals in the inner Solar System.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009