It’s a staple of disaster movies: a huge space rock hurtles towards Earth and the hero gloriously self-sacrifices in a nuclear fireball to save humankind. In reality, saving the planet from an oncoming asteroid will be less action hero and more acting together: countries need to plan well ahead and synchronise their approach to make sure Earth is prepared. But current preparation efforts are scattered and uncoordinated. International Asteroid Day is the perfect time to review how ready humankind is and what more remains to be done. Near-Earth objects such as asteroids, meteoroids and comets imperil the planet. They have been implicated in previous mass extinctions, including that of the dinosaurs. An object hitting land could produce a crater kilometres across, rattling faraway infrastructure and blanketing the planet in dust, with knock-on effects for the climate. An ocean splashdown could cause a tsunami higher than most buildings just a few hours later. When space objects hit the Earth’s surface they are called meteorites – and they have arrived within human history. The Kaali meteorite crater formed on the island of Saaremaa, Estonia, several millennia ago. Scientists still debate exactly when the meteorite landed and what its effects were for any humans living there at the time. Even an object skimming through or breaking up in the atmosphere is dangerous. These objects are called meteors, and they have dangerously impacted Russia at least twice. On 30 June 1908, a still undetermined object blasted Tunguska in Siberia. It incinerated and toppled trees, and caused shockwaves felt dozens of kilometres away. On 15 February 2013 a meteor broke up over Chelyabinsk, shattering glass and setting off car alarms. More than 1,600 people were injured.
Rather than cleaning up afterwards, it would be better to stop space objects from reaching Earth in the first place. The best plan is to deflect the object so it misses Earth entirely. For that, early detection is key. The further away the object is, the less of a nudge it needs: a fraction of a degree change in its course expands over time to become a huge deviation. But the more distant the object, the longer it takes for a deflection measure to reach it. This emphasises the need for early planning.
Possible deflection plans come from science and science fiction. A large water tank could be landed on the object’s surface and then pierced with a small hole. As the water in the tank vents into space it would propel the space object like a rocket engine. More simply, any form of engine could be attached to the object.
