Radar and Optical Observations of Asteroid 1998 KY26.

Ostro, S. J., P. Pravec, L. A. M. Benner, R. S. Hudson, L. Sarounova, 
  M. D. Hicks, D. L. Rabinowitz, J. V. Scotti, D. J. Tholen, M. Wolf, 
  R. F. Jurgens, M. L. Thomas, J. D. Giorgini, P. W. Chodas, 
  D. K. Yeomans, R. Rose, R. Frye, K. D. Rosema, R. Winkler, M. A. Slade.

Science 285, 557-559 (1999).


Abstract:

Observations of near-Earth asteroid 1998 KY26 shortly after its 
discovery reveal a slightly elongated spheroid with a diameter of about 
30 m, a composition analogous to carbonaceous chondritic 
meteorites, and a rotation period of 10.7 minutes, which is an order of 
magnitude shorter than that measured for any other solar system 
object.  The rotation is too rapid for 1998 KY26 to consist of multiple 
components bound together just by their mutual gravitational 
attraction. This monolithic object probably is a fragment derived from 
cratering or collisional destruction of a much larger asteroid.