Editor's Summary
10 July 2008
Binary asteroids: Satellites formed from the rubble
Many asteroids and trans-neptunian objects have satellites: the tally stands at over 150 on http://tinyurl.com/dweqf. The smallest of these binary systems are main-belt and near-Earth asteroids, but the environments of these two types of object are very different, making it difficult to work out a common mechanism to explain their formation. Now Walsh et al. present a model that fits the bill. Properties of the observed main-belt and near-Earth asteroids with satellites are matched by simulations involving the slow spinup of a 'rubble pile' asteroid via the thermal YORP effect (where radiation from an irregular body exerts a net force on that body). The mass shed from the equator of a spinning body accretes into a satellite if the material consists of particles undergoing energy-dissipating collisions.
News and Views: Asteroids: How to make a flying saucer
Wherever we look in the Solar System, small bodies often seem to come in twos. Simulations show how asteroids spun in the Sun can produce such pairings — one of whose members acquires a strangely familiar shape.
William F. Bottke
doi:10.1038/454173a
Letter: Rotational breakup as the origin of small binary asteroids
Kevin J. Walsh, Derek C. Richardson & Patrick Michel
doi:10.1038/nature07078
