A civilisation-destroying asteroid may sound like the stuff of science fiction, but the threat is very real. These rocky fragments range in size from mere metres to hundreds of kilometres across, and while most of them orbit the Sun in a belt between Mars and Jupiter, the gravitational pull of planets can sometimes alter their path. If an asteroid – or a fragment of one, known as a meteoroid – makes it to Earth’s atmosphere, it usually burns up as a meteor or shooing star. However, some explode in a massive fireball, and others make it down to Earth’s surface as meteorites.
In 2013, a 10,000-tonne meteor measuring 18 metres (59 feet) across hurtled into Earth’s atmosphere at 67,000 kilometres (41,600 miles) per hour before exploding 23.3 kilometres (14.4 miles) above the Russian city of Chelyabinsk. More than 1,000 people were injured as a result of the fireball, mainly by shattered glass caused by the shock wave, though luckily nobody was killed. The surprise explosion released more than 30 times the energy than that from the Hiroshima atomic bomb. To put that into perspective, the massive meteor strike that is thought to have triggered the extinction of the dinosaurs measured around ten kilometres (6.2 mile) across and released around a billion times the energy of an atomic bomb. Before impact, the asteroid was completely undetected because it was “too small for the survey telescopes and came at us out of the Sun”, according to NASA. The potentially catastrophic incident highlighted just how important it is to monitor near-Earth objects (NEOs) – comets and asteroids that have been
