Nudging asteroids: white paint, rockets, gravity, and other ways of saving life on Earth

Asteroid 2005 YU55, which will be the Earth’s closest encounter with an object of such scale in 30 years. AAP/AFP/NASA/JPL-Caltech

The 400-metre-long lump of carbon, magnesium, oxygen and “a whole bunch of other stuff” whizzing by, closer to the Earth than the moon, could have been nudged out of our path had it needed to be, says astronomer Paul Francis.

Dr Francis, of the Australian National University, said that given sufficient notice (“a few decades”), humans had a number of good options if asteroid 2005 YU55 - which is travelling at about 13 kilometres per second - or one of its peers was on a collision course.

“What you’d want to do is change its orbit slightly; there have been a number of suggestions, including strapping a rocket to its side and giving it a gentle sideways nudge,” Dr Francis said. “If you catch it early enough, it doesn’t take much of a nudge to mean that it misses the Earth. Another possibility is to paint half of it white, because as the wind from the sun settles on one half differently from on the other half it will also change the orbit,” he said.

Other options included hovering a space craft nearby: “Given enough time, the gravity of the spacecraft will pull the asteroid sideways,” Dr Francis said.

Unfortunately for fans of nuclear weapons, firing them at asteroids is not on the menu for Dr Francis, who once received a science prize for his joint discovery that most black holes are pink. “You don’t want to nuke it or you’d be confronted by 100 medium sized asteroids rather than one big one,” he said.

The 2005 YU55 asteroid has been tracked for six or seven years in its path towards us from the asteroid belt, said Dr Francis. “The really good surveys have only been going for the last 10 years or so. The big ones, the ones several kilometres in size, the ones that could wipe out the entire earth, about 90 to 95 per cent of them have been mapped so far. This one is a medium sized one, less than a kilometre, and we’ve got about 50 per cent of them mapped.”

“If we had a few decades warning, there’s quite a bit we could do.”

The asteroid, 2005YU55 will pass about 324,000 kilometres from Earth today. Watch NASA’s video about the asteroid below.

An artist’s animation that illustrates a massive asteroid belt in orbit around a star the same age and size as our Sun. Asteroids are chunks of rock from “failed” planets, which never managed to coalesce into full-sized planets. Asteroid belts can be thought of as construction sites that accompany the building of rocky planets. Announced on April 28, 2010, scientists using NASA�s Infrared Telescope Facility have detected water-ice and carbon-based organic compounds on the surface of an asteroid. The cold hard facts of the discovery of the frosty mixture on one of the asteroid belt’s largest occupants, suggests that some asteroids, along with their celestial brethren, comets, were the water carriers for a primordial Earth. AAP/AFP/NASA/JPL-CALTECH