A Tumbling Apophis: Good News for Earth
Asteroid 99942 Apophis has been worrisome ever since its discovery in 2004. Estimated to be a bit more than 1,000 feet (300 m) across, it would deliver the kinetic-energy equivalent of 500 megatons of TNT were it to strike Earth — which it might well do some day. At first, dynamicists predicted a dangerously close pass in 2029 and a 3% chance of collision. More observations eased those fears — but triggered worry instead about a threatening flyby in March 2036.