@article{f46916d4f1504224b9402356c14eeaa9,
title = "Spectral properties and composition of potentially hazardous Asteroid (99942) Apophis",
abstract = "The known close approach of Asteroid (99942) Apophis in April 2029 provides the opportunity for the case study of a potentially hazardous asteroid in advance of its encounter. The visible to near-infrared (0.55 to 2.45 μm) reflectance spectrum of Apophis is compared and modeled with respect to the spectral and mineralogical characteristics of likely meteorite analogs. Apophis is found to be an Sq-class asteroid that most closely resembles LL ordinary chondrite meteorites in terms of spectral characteristics and interpreted olivine and pyroxene abundances, although we cannot rule out some degree of partial melting. A meteorite analog allows some estimates and conjectures of Apophis' possible range of physical properties such as the grain density and micro-porosity of its constituent material. Composition and size similarities of Apophis with (25143) Itokawa suggest a total porosity of 40% as a {"}current best guess{"} for Apophis. Applying these parameters to Apophis yields a mass estimate of 2 × 1010 kg with a corresponding energy estimate of 375 Mt for its potential hazard. Substantial unknowns, most notably the total porosity, allow uncertainties in these mass and energy estimates to be as large as factors of two or three.",
keywords = "Asteroids, Meteorites, Spectroscopy, composition",
author = "Binzel, {Richard P.} and Rivkin, {Andrew S.} and Thomas, {Cristina A.} and Pierre Vernazza and Burbine, {Thomas H.} and DeMeo, {Francesca E.} and Bus, {Schelte J.} and Tokunaga, {Alan T.} and Mirel Birlan",
note = "Funding Information: We thank our MIT colleagues Paul Schechter, Josh Winn, and Elisabeth Adams for performing the Magellan observations and Susan Kern for the software routines used for the initial processing of the Magellan data. R.P.B. thanks the Observatoire de Paris Institut de Mecanique Celeste et de Calcul des Ephemerides et Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique for their collaboration and hospitality during the completion of this manuscript. We thank P. Abell and D. Britt for their constructive reviews. Observations reported here were obtained at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement NCC 5-538 with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. This research utilizes meteorite spectra obtained from the NASA RELAB facility at Brown University. This material is based upon work supported by the National Science Foundation under Grant 0506716 and NASA under Grant NAG5-12355. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or NASA.",
year = "2009",
month = apr,
doi = "10.1016/j.icarus.2008.11.028",
language = "English (US)",
volume = "200",
pages = "480--485",
journal = "Icarus",
issn = "0019-1035",
publisher = "Academic Press Inc.",
number = "2",
}