‘Big bang’ a real threat

TO PREDICT – AND INTERCEPT – NEXT EARTH-BOUND ASTEROID ‘Risk that Earth will get hit in a devastating event one day is very high.’

Throughout its 4.5 billion-year history, Earth has been repeatedly pummelled by space rocks that have caused anything from an innocuous splash in the ocean to species annihilation.

When the next big impact will be, nobody knows.

But the pressure is on to predict – and intercept – its arrival.

“Sooner or later we will get ... a minor or major impact,” Rolf Densing, who heads the European Space Operations Centre (Esoc) in Darmstadt, Germany, said ahead of International Asteroid Day tomorrow.

It may not happen in our lifetime, he said, but “the risk that Earth will get hit in a devastating event one day is very high.”

For now, there is little we can do.

And yet, the first-ever mission to crash a probe into a small space rock to alter its trajectory suffered a major setback when European ministers declined in December to fund part of the project.

“We are not ready to defend ourselves” against an Earth-bound object, said Densing. “We have no planetary defence measures.”

Hitherto relegated to the realms of science fiction, tactics could include nuking an incoming asteroid, using lasers to vaporise it, sending a space “tractor” to drag it off course, or bumping it into a new direction.

But first, we need to be able to spot the threat.

Astrophysicists monitoring the risk classify objects into sizes ranging from a few millimetres to behemoths 10km across – the size of rock that wiped out non-avian dinosaurs some 65 million years ago.

The smallest type enter Earth’s atmosphere daily, burning up prettily as shooting stars.

The largest occur once every 100 million years, and the next impact could well ring in the end of human civilisation. But when would it happen? So far, experts have managed to list more than 90% of asteroids in the dino-killing range, and determined that none poses an immediate threat.

A much bigger concern is the whereabouts of millions of asteroids in the 15- to 140-metre range.

One such object, a 40-metre space rock, caused the largest impact in recent history when it exploded over Tunguska, Siberia, on June 30, 1908 – the date on which Asteroid Day is marked.

The blast flattened some 80 million trees over 2 000 sparsely-populated square kilometres – an area bigger than greater London. Tunguska-sized events happen, on average, every 300 years or so.

“Imagine that this type of asteroid would fall in a very populated area like Paris or Germany, I mean this is something that would be really, really a catastrophe,” said Nicolas Bobrinsky, programme manager of the European Space Agency’s Space Situational Awareness project, which surveys asteroids. At least the ones it knows of. The Chelyabinsk impact in 2013, for example, caught everyone unawares.

A once-a-decade category rock of about 20 metres exploded in the atmosphere over central Russia with the kinetic energy of some 27 Hiroshima bombs.

The United Nations declared June 30 International Asteroid Day to raise public awareness about what event organisers describe as “humanity’s greatest challenge”.

The initiative has the backing of dozens of scientists, astronauts and celebrities, many of whom will take part in a special 24-hour live broadcast tomorrow. – AFP