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Albedos of Near Earth Asteroids

Jessie Dotson
Asteroid Population Characterization
Delivered As: 
Abstract Text: 

NEA characterization is important for assessing the risk that the population of NEAs pose to the Earth via possible atmospheric entry and impact. Most NEAs are only characterized by their absolute magnitude (Hmag) and their orbital parameters. A statistical assessment of the properties of NEAs is often utilized to estimate diameters, specifically through the Hmag-Diameter relationship that depends inversely on square-root of the albedo. A canonical understanding of the relationship between surface composition and albedo has come from studying vast numbers of asteroids in the Main Belt. Dynamical studies of the asteroid belt indicate what areas feed into the NEA population, so there are predictions for what compositions, and by association, what distribution of albedos should be in the NEA population. In recent years, there has been a rapid increase in the number of NEAs with measured albedos, mostly through the WISE, NEOWISE and Spitzer Warm Mission's ExploreNEOs program. One surprise is existence of significant numbers of very low albedo NEAs, with albedos less 4%, found by WISE/NEOWISE. The WISE/NEOWISE albedo distribution, when adopted instead of the prior albedo distribution determined by Stuart and Binzel (2004), considerably increases the apparent risk of NEAs with large Hmag because some fraction of NEAs are assigned relationally larger diameters through the Hmag-Diameter relation; larger diameters mean larger energies upon atmospheric entry. The prior albedo distribution by Stuart and Binzel (2004) was debiased (with respect to detection) and based upon only ~36 NEAs with measured albedos. Now the numbers of NEAs with measured albedos has increased more than tenfold. We present the results of and implications for a debiased NEA albedo distribution using the current sample of NEA albedos and employing a similar debiasing approach to Stuart and Binzel. We will compare albedos with taxonomic surface compositions for the sample of NEAs for which both are measured. We will look for correlations between albedo and NEA orbit families (Aten, Apollo, Amor) with this larger sample.

T. Robinson, University of Washington
SSERVI Identifier: 

Recognizing that science and human exploration are mutually enabling, NASA created the Solar System Exploration Research Virtual Institute (SSERVI) to address basic and applied scientific questions fundamental to understanding the Moon, Near Earth Asteroids, the Martian moons Phobos and Deimos, and the near space environments of these target bodies. As a virtual institute, SSERVI funds investigators at a broad range of domestic institutions, bringing them together along with international partners via virtual technology to enable new scientific efforts."