Spectral properties of near-Earth and Mars-crossing asteroids using Sloan photometry

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 2016-04, Vol.268 (C), p.340-354
• Main Authors: Carry, B., Solano, E., Eggl, S., DeMeo, F.E.
• Format: Article
• Language: English
• Subjects: Asteroids; Asteroids, composition; Astrophysics; Classification; Earth; Encounters; Near-Earth objects; Photometry; Populations; Sciences of the Universe; Sky surveys (astronomy); Taxonomy
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2015.12.047

•We search SDSS image archive for near-Earth (NEA) and Mars-crosser (MC) asteroids.•We report on the taxonomic classification of 206 NEA and 776 MC.•We study NEA source regions and confirm the inner main belt as a major source.•We develop a force model on surface grain and study planetary encounters.•The fresher surfaces have statistically more encounters with Venus and Earth. The nature and origin of the asteroids orbiting in near-Earth space, including those on a potentially hazardous trajectory, is of both scientific interest and practical importance. We aim here at determining the taxonomy of a large sample of near-Earth and Mars-crosser asteroids and analyze the distribution of these classes with orbit. We use this distribution to identify the source regions of near-Earth objects and to study the strength of planetary encounters to refresh asteroid surfaces. We measure the photometry of these asteroids over four filters at visible wavelengths on images taken by the Sloan Digital Sky Survey (SDSS). These colors are used to classify the asteroids into a taxonomy consistent with the widely used Bus-DeMeo taxonomy (DeMeo et al. [2009]. Icarus 202, 160–180) based on visible and near-infrared spectroscopy. We report here on the taxonomic classification of 206 near-Earth and 776 Mars-crosser asteroids determined from SDSS photometry, representing an increase of 40% and 663% of known taxonomy classifications in these populations. Using the source region mapper by Greenstreet et al. (Greenstreet, S., Ngo, H., Gladman, B. [2012]. Icarus, 217, 355–366), we compare for the first time the taxonomic distribution among near-Earth and main-belt asteroids of similar diameters. Both distributions agree at the few percent level for the inner part of the main belt and we confirm this region as a main source of near-Earth objects. The effect of planetary encounters on asteroid surfaces are also studied by developing a simple model of forces acting on a surface grain during planetary encounter, which provides the minimum distance at which a close approach should occur to trigger resurfacing events. By integrating numerically the orbit of the 519 S-type and 46 Q-type asteroids in our sample back in time for 500,000years and monitoring their encounter distance with Venus, Earth, Mars, and Jupiter, we seek to understand the conditions for resurfacing events. The population of Q-type is found to present statistically more encounters with Venus and the Earth than S-types, altho