Red Lightning — John Varley

The son of one of the first men to fly to Mars and back, Ray Garcia-Strickland is now a disgruntled Martian, tired of the Red Planet's overdevelopment and the gravity-dependent tourist Earthies. But that doesn't stop him from fearing the worst when Earth is struck by an unknown object, causing a massive tsunami. Living high on his father's glory was okay, but now Ray must literally come down to Earth-and solve one of its greatest mysteries.