Jay Melosh, a Purdue University asteroid impact expert, says an object of similar size -- as big as an aircraft carrier -- colliding with Earth would result in a 4,000-megaton blast, a magnitude 7.0 earthquake and, if it struck in the deep ocean, 70-foot-high tsunami waves 60 miles from the splashdown site.
His estimate comes as NASA scientists said asteroid 2005 YU55 will pass between Earth and the moon Nov. 8, coming within 201,000 miles of Earth on its closest approach, a Purdue release said Monday.
"What is unique about this asteroid flyby is that we were aware of it well in advance," Melosh said. "Before about 1980 we wouldn't know about an asteroid of this size until it was already making a close pass, but now it is unlikely that such an asteroid will approach the Earth without our knowledge.
"Impacts from asteroids of this size are very rare," he said. "They occur about once every 100,000 years, so the chances of an actual collision with an asteroid like YU55 is about 1 percent in the next thousand years."