Tiny Main-belt Asteroid Spectral Survey (TMASS)

Johns Hopkins University, Baltimore MD

Investigators

Abstract

AST 0708101 Rivkin A long-standing problem in asteroid spectroscopy has been the question of whether the spectra of these bodies change with time via exposure to the solar wind and/or micrometeorite impact, a process dubbed "space weathering". Recent evidence is coalescing around the theory that space weathering does occur on asteroid surfaces, and that the 1-5 km diameter range is a critical transition size. This research program led by Dr. Andrew Rivkin will use newly-collected astronomical data to explore space weathering in a sample free of many uncertainties present in other studies. The extent and rate of space weathering on asteroids will be measured by collecting the visible and near-IR reflectance spectra of roughly 100 asteroids in the Koronis dynamical family. National facilities (the 4-m telescope at Kitt Peak and the Infrared Telescope Facility (IRTF)) as well as facilities associated with the researchers' institutions (Apache Point Observatory in New Mexico for Rivkin, the Magellan telescopes in Chile for Binzel) will be used for observations. The targets will be objects in the 1-5 km diameter range, which have not been systematically studied in the main belt. The result of this work will be a better understanding of the surface processes on and composition of asteroids. A study of Near-Earth Object (NEO) spectra indicates that objects roughly 1 km and smaller on average show little evidence of space weathering, while those 5 km and larger have average spectra like large main-belt objects. This is consistent with the buildup of weathering products with time on asteroid surfaces. However, studies that have been done must assume the NEOs have the same composition and weathering styles and rates as each other and of main-belt asteroids. By observing small members of a dynamical family and comparing them to larger members of the same family, that issue will be removed. By establishing and measuring the degree (or absence) of space weathering in the Koronis family, the amount that spectra can change due to this process, and the road to correcting for it (as appropriate) in making compositional interpretations will be determined. The team have obtained, reduced, and published a large quantity of visible and infrared asteroid spectra, and are well-qualified to undertake this project. Establishing and characterizing the extent of space weathering on asteroids is directly applicable to understanding their composition and nature. Although not a near-term prospect, asteroid mining applications will be interested in determining the true composition of surfaces, not the weathered appearance. The same is true of NEO mitigation concerns; a metal-rich object could appear so due to space weathering or a high concentration of metal. This study will help unravel those two possibilities, which are of obvious importance if such an object had to be deflected or destroyed. The data collected will be made publicly available as quickly as is practical. The research team have done this before for other data, as part of the NSF-funded MIT-IRTFUH NEO survey (http://smass.mit.edu/minus.html). ***