From Magnitudes to Diameters: The Albedo Distribution of Near Earth Objects and the Earth Collision Hazard

Abstract A recently published model of the Near Earth Object (NEO) orbital–magnitude distribution (Bottke et al. , 2002, Icarus 156 , 399–433.) relies on five intermediate sources for the NEO population: the ν 6 resonance, the 3:1 resonance, the outer portion of the main belt (i.e., 2.8–3.5 AU), the Mars-crossing population adjacent to the main belt, and the Jupiter family comet population. The model establishes the relative contribution of these sources to the NEO population. By computing the albedo distribution of the bodies in and/or near each of the five sources, we can deduce the albedo distribution of the NEO population as a function of semimajor axis, eccentricity, and inclination. A problem with this strategy, however, is that we do not know a priori the albedo distribution of main belt asteroids over the same size range as observed NEOs (diameter D H thr , beyond which we assumed that the families' absolute magnitude distributions were background-like. We found that H thr =14.5 provides the best match to the color vs heliocentric distance distribution observed by the Sloan Digital Sky Survey. With this value of H thr our model predicts that the debiased ratio between dark and bright (albedo smaller or larger than 0.089) objects in any absolute-magnitude -limited sample of the NEO population is 0.25±0.02. Once the observational biases are properly taken into account, this agrees very well with the observed C/S ratio (0.165 for H size -limited sample is considered. We estimate that the total number of NEOs larger than a kilometer is 855±110, which, compared to the total number of NEOs with H H =18↞ D =1 km slightly overestimates the number of kilometer-size objects. Combining our orbital distribution model with the new albedo distribution model, and assuming that the density of bright and dark bodies is 2.7 and 1.3 g/cm 3 , respectively, we estimate that the Earth should undergo a 1000 megaton collision every 63,000±8000 years. On average, the bodies capable of producing 1000 megaton of impact energy are those with H

[1]  Robert Jedicke,et al.  Earth and space-based NEO survey simulations: prospects for achieving the Spaceguard Goal , 2003 .

[2]  G. Duvert,et al.  Discovery of a moon orbiting the asteroid 45 Eugenia , 1999, Nature.

[3]  Z. Ivezic,et al.  Solar system objects observed in the Sloan Digital Sky Survey commissioning data , 2001 .

[4]  Robert A Kolvoord,et al.  Collision lifetimes and impact statistics of near-Earth asteroids , 1993 .

[5]  Paolo Tanga,et al.  On the Size Distribution of Asteroid Families: The Role of Geometry , 1999 .

[6]  D. Rabinowitz,et al.  A reduced estimate of the number of kilometre-sized near-Earth asteroids , 2000, Nature.

[7]  M. Di Martino,et al.  Physical properties of near-Earth asteroids , 1998 .

[8]  Eugene M. Shoemaker,et al.  Asteroid and comet flux in the neighborhood of the earth , 1988 .

[9]  D. Jewitt,et al.  On the relative numbers of C types and S types among near-earth asteroids , 1989 .

[10]  J. Miller,et al.  The Shape of Eros from NEAR Imaging Data , 2000 .

[11]  David Morrison,et al.  THE IMPACT HAZARD: , 2021, Hazards Due to Comets and Asteroids.

[12]  R. Jedicke,et al.  The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids , 1998 .

[13]  Stephan D. Price,et al.  The Supplemental IRAS Minor Planet Survey , 2002 .

[14]  Andrea Milani,et al.  Dynamics of Earth‐crossing asteroids: the protected Toro orbits , 1998 .

[15]  D. Britt,et al.  Asteroid Density, Porosity, and Structure , 2002 .

[16]  Farquhar,et al.  Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby , 1997, Science.

[17]  M. E. Davies,et al.  Bulk density of asteroid 243 Ida from the orbit of its satellite Dactyl , 1995, Nature.

[18]  G. W. Wetherill,et al.  Collisions in the asteroid belt , 1967 .

[19]  J. S. Stuart,et al.  A Near-Earth Asteroid Population Estimate from the LINEAR Survey , 2001, Science.

[20]  Andrew Scott Rivkin,et al.  Hydrated Minerals on Asteroids: The Astronomical Record , 2003 .

[21]  Eugene M. Shoemaker,et al.  ASTEROID AND COMET BOMBARDMENT OF THE EARTH , 1983 .

[22]  Robert Jedicke,et al.  The Mass Disruption of Oort Cloud Comets , 2002, Science.

[23]  Jedicke,et al.  Understanding the distribution of near-earth asteroids , 1999, Science.

[24]  Giovanni B. Valsecchi,et al.  Close approaches of asteroid 1999 AN10: resonant and non-resonant returns , 1999 .

[25]  M. Nolan,et al.  Velocity Distributions among Colliding Asteroids , 1994 .

[26]  Alan W. Harris,et al.  Application of photometric models to asteroids. , 1989 .

[27]  D. Morrison.  The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop , 1992 .

[28]  E. Tedesco,et al.  Compositional Structure of the Asteroid Belt , 1982, Science.

[29]  Paolo Tanga,et al.  The Velocity–Size Relationship for Members of Asteroid Families and Implications for the Physics of Catastrophic Collisions , 1999 .

[30]  Edward F. Tedesco,et al.  Asteroid Albedos and Diameters , 1994 .

[31]  W. Bottke,et al.  Origin and Evolution of Near-Earth Objects , 2002 .

[32]  Richard Greenberg.  Orbital interactions - A new geometrical formalism , 1982 .

[33]  Alberto Cellino,et al.  Asteroid Families: Search of a 12,487-Asteroid Sample Using Two Different Clustering Techniques , 1995 .

[34]  P. Farinella,et al.  Origin, Aging, and Death of Asteroid Families , 1999 .

[35]  Robert Jedicke,et al.  Detection of Near Earth Asteroids Based Upon Their Rates of Motion , 1996 .

[36]  Alessandro Morbidelli,et al.  Orbital and temporal distributions of meteorites originating in the asteroid belt , 1998 .

[37]  R. Jedicke,et al.  Debiased Orbital and Absolute Magnitude Distribution of the Near-Earth Objects , 2002 .