1. Southwest Research Institute, 1050 Walnut St, Suite 426, Boulder, Colorado 80302, USA

Correspondence to: David Nesvorný Correspondence and requests for materials should be addressed to D.N. (e-mail: Email: davidn@boulder.swri.edu).

Abstract

The present population of asteroids in the main belt is largely the result of many past collisions^{1, 2}. Ideally, the asteroid fragments resulting from each impact event could help us understand the large-scale collisions that shaped the planets during early epochs^{3, 4, 5}. Most known asteroid fragment families, however, are very old and have therefore undergone significant collisional and dynamical evolution since their formation⁶. This evolution has masked the properties of the original collisions. Here we report the discovery of a family of asteroids that formed in a disruption event only 5.8 0.2 million years ago, and which has subsequently undergone little dynamical and collisional evolution^{5, 6}. We identified 39 fragments, two of which are large and comparable in size (diameters of 19 and 14 km), with the remainder exhibiting a continuum of sizes in the range 2–7 km. The low measured ejection velocities suggest that gravitational re-accumulation after a collision may be a common feature of asteroid evolution. Moreover, these data can be used to check numerical models of larger-scale collisions⁸.

1. Southwest Research Institute, 1050 Walnut St, Suite 426, Boulder, Colorado 80302, USA

Correspondence to: David Nesvorný Correspondence and requests for materials should be addressed to D.N. (e-mail: Email: davidn@boulder.swri.edu).