Earth Planets Space, Vol. 53 (No. 11), pp. 1065-1069, 2001
Lunar Mission Research Center, National Space Development Agency of Japan, Tsukuba Space Center, 2-1-1 Sengen, Tsukuba City, Ibaraki 305-8505, Japan
(Received January 12, 2001; Revised September 20, 2001; Accepted September 20, 2001)
Abstract: The strength of an asteroid is a valuable parameter, but it is difficult to measure directly. Although impact experiments have made a large contribution, the problem of the relationship between an asteroid's size and its strength has not been solved. This paper introduces a valuable parameter for natural bodies, the power-law index f of the size distribution of fracture planes [NS= kSS-]. This index can be regarded as parameterizing the strength, because strength is controlled by the size of the largest fracture. The power-law indices f of the Martian satellite Phobos and the asteroid Gaspra were found to be 5.9 and 6.5, respectively. These values are close to 6, which is the theoretical value expected for the "fully cracked" condition of Housen and Holsapple (1999). The implications of this result for the size-strength relationship of asteroids are discussed.