title: Super-catastrophic disruption of asteroids at small perihelion distances.
abstract: Most near-Earth objects came from the asteroid belt and drifted via non-gravitational thermal forces into resonant escape routes that, in turn, pushed them onto planet-crossing orbits. Models predict that numerous asteroids should be found on orbits that closely approach the Sun, but few have been seen. In addition, even though the near-Earth-object population in general is an even mix of low-albedo (less than ten per cent of incident radiation is reflected) and high-albedo (more than ten per cent of incident radiation is reflected) asteroids, the characterized asteroids near the Sun typically have high albedos. Here we report a quantitative comparison of actual asteroid detections and a near-Earth-object model (which accounts for observational selection effects). We conclude that the deficit of low-albedo objects near the Sun arises from the super-catastrophic breakup (that is, almost complete disintegration) of a substantial fraction of asteroids when they achieve perihelion distances of a few tens of solar radii. The distance at which destruction occurs is greater for smaller asteroids, and their temperatures during perihelion passages are too low for evaporation to explain their disappearance. Although both bright and dark (high- and low-albedo) asteroids eventually break up, we find that low-albedo asteroids are more likely to be destroyed farther from the Sun, which explains the apparent excess of high-albedo near-Earth objects and suggests that low-albedo asteroids break up more easily as a result of thermal effects.
authors.affiliation: Department of Physics, PO Box 64, 00014 University of Helsinki, Finland.|Finnish Geospatial Research Institute, PO Box 15, 02430 Masala, Finland.
authors.forename: Mikael
authors.initials: M
authors.lastname: Granvik
authors.affiliation: Observatoire de la Cote d'Azur, Boulevard de l'Observatoire, F 06304 Nice Cedex 4, France.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Morbidelli
authors.affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Jedicke
authors.affiliation: Observatoire de la Cote d'Azur, Boulevard de l'Observatoire, F 06304 Nice Cedex 4, France.|Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA.
authors.forename: Bryce
authors.initials: B
authors.lastname: Bolin
authors.affiliation: Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, Colorado 80302, USA.
authors.forename: William F
authors.initials: WF
authors.lastname: Bottke
authors.affiliation: University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721-0065, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Beshore
authors.affiliation: Institute of Astronomy, Charles University, V Holešovikách 2, CZ 18000 Prague 8, Czech Republic.
authors.forename: David
authors.initials: D
authors.lastname: Vokrouhlický
authors.affiliation: Observatoire de la Cote d'Azur, Boulevard de l'Observatoire, F 06304 Nice Cedex 4, France.
authors.forename: Marco
authors.initials: M
authors.lastname: Delbò
authors.affiliation: Observatoire de la Cote d'Azur, Boulevard de l'Observatoire, F 06304 Nice Cedex 4, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Michel