A GERMAN schoolboy of 13 revised NASA calculations, upping the estimate of the risk that the asteroid Apophis will impact the Earth.

The Potsdamer Neuerster Nachrichten reported Tuesday that Nico Marquardt used orbital observations from the Astrophysics Institute of Potsdam to correct NASA's original estimate of a 1 in 45,000 chance of a collision up to 1 in 450.

He considered that the asteroid might collide with any one or more of 40,000 satellites during its next closest approach to Earth, which will occur on April 13, 2029.

The satellites orbit the planet at up to 35,880 kilometers altitude, moving at 1.9 miles (3.07 kilometres) per second. The asteroid Apophis will pass by Earth at 32,500 kilometres distance.

If Apophis hits one or more satellite(s) in 2029, that could alter its solar orbit enough to make it impact Earth on its next pass in 2036.

NASA had apparently overlooked the chance that Apophis might hit a satellite or two in 2029. It reportedly told the European Space Agency that Marquardt's revised estimate is correct.

Asteroid Apophis is a mass of solid iron and indium 320 meters in diameter and weighing 200 billion tons. If it impacts Earth, the event will be catastrophic. A similar asteroid impact in the Gulf of Mexico millions of years ago is thought to have killed off the dinosaurs.

The AFP story is here.