3-μm LIGHT ABSORPTION BY HYDROXYL OF SOLAR WIND ORIGIN AND THE PROSPECTS FOR WATER DETECTION ON ASTEROIDS WITH NIR SPECTROSCOPY

摘要

Chemical trapping of solar wind protons and formation of OH~- -groups near the surfaces of regolith particles on atmosphereless celestial bodies can result in absorption band near 3 μm in their reflectance spectra. Theoretical simulation of the band shows that it may exceed in depth 3-μm bands found with low-resolution spectro-scopy. The shape, width, and position of solar-wind-induced 3-μm band may resemble those observed in high-resolution spectra of asteroids and H_2O- and OH -containing minerals. Yet, 3-μm absorption of Ceres and Pallas is found to be deep enough to assign it to hydrated minerals. To prove the presence of H_2O-molecules, detection of 3- or 1.4-μm band should be accompanied by high-resolution observation of 2-μm band which can be distinguished from that of orthopyroxene by the shape and width.