On March 16, 2880, a 1.1-kilometer diameter asteroid known as 1950 DA is scheduled to swing so close to Earth that it could crash into the ocean. The probability of impact is small, but should it occur, scientists say, it could generate tsunami waves hundreds of feet high that would drench coastal areas.

Scientists announced last spring that 1950 DA had about a 0.3 percent chance of slamming into Earth. In the new work, which appears in the June issue of the Geophysical Journal International, Steven Ward and Erik Asphaug of the University of California, Santa Cruz, created a computer simulation of what might happen if the space rock touched down 600 kilometers east of the U.S. coastline (with oceans covering 70 percent of the earth's surface, a water landing is probable). Hurtling earthward at 17.8 kilometers a second, 1950 DA would blast a cavity 19 kilometers across in the sea and set into motion a series of tsunamis hundreds of meters high, they determined. Within two hours, 100-meter-high killer waves would break on the East Coast; within 12 hours 20-meter waves would reach Europe and Africa.

The researchers acknowledge that the likelihood of 1950 DA colliding with our planet in some 880 years is "vanishingly rare." Still, Ward observes, "from a geologic perspective, events like this have happened many times in the past. Asteroids the size of 1950 DA have probably struck the Earth about 600 times since the age of the dinosaurs." Rarity, the authors conclude, "requires perspective."