"STRANGE WORLDS: RADAR ENCOUNTERS WITH EARTH-APPROACHING ASTEROIDS"
The Earth exists in a swarm of asteroids that includes
the cheapest destinations
of missions beyond the Earth-Moon system. Radar
echoes can furnish
high-resolution images of near-Earth asteroids, reveal
their rotation states
and metal abundances, and improve the accuracy of trajectory
predictions a
thousandfold. Radar observations have revealed
a variety of exotic NEAs,
including a contact binary, a world shaped like a paramecium,
a 2-km chunk of
metal, two non-principal-axis rotators, and a spheroidal,
carbonaceous, rapidly
rotating monolith. Video animations using radar-based
computer models convey
the unusual nature of these asteroids and are helping
us to study the dynamics
of orbits close to them and the physics of collisions
into them.