About 50 million coastal residents are vulnerable

Researchers have assumed that tsunamis would make ocean impacts more deadly than those on land.

Waves radiating from the impact of a 300-metre-wide asteroid would carry 300 times more energy than the 2004 Asian tsunami. "There still are a lot of uncertainties," Chesley cautions. The solar system's population of 100 m to 400 m asteroids is poorly known".

In 2004, a newly discovered 320m asteroid, 99942 Apophis (previously called 2004 MN4), achieved the highest impact probability of any potentially dangerous object. The probability of collision on 13 April 2029 was estimated to be as high as 1 in 17 by Steve Chesley of NASA's Jet Propulsion Laboratory though the worst published figure was 1 in 37 calculated in December 2004. Later observations showed that the asteroid will miss the earth by 25,600 km (within the orbits of communications satellites) in 2029, but its orbit will be altered unpredictably in a way which does not rule out a collision on 13 or 14 April 2035 or later in the century. These possible future dates have a cumulative probability of 1 in 6000 for an impact in the 21^stcentury.

If you would like to see previous impacts craters using Google Earth click here. Or how about seeing future impact events as detected by NASA