Ages 7-10.     There's a comet speeding in from the outer solar system, and it's about to slam into an asteroid. Who will be left standing after this interplanetary smackdown? The pockmarked asteroid, a veteran fighter who's already seen some action? Or the dazzling comet, with its incredible velocity and a tail that stretches millions of miles? Asteroid vs. Comet starts by comparing the two opponents, then offers hints and context to encourage readers to use real science to form a hypothesis.      48 pages  hc