The surprise discovery of asteroid 2024 RW1, mere hours before it hit Earth harmlessly this week, may have you wondering whether we are at risk of larger space rocks coming out of nowhere and wreaking devastation. Thankfully, our ability to track asteroids is on the rise, even if we can鈥檛 catch them all.
鈥淲e believe we know more than 90 per cent of the asteroids that are about one kilometre in size, where one kilometre is considered, not a planet killer, but something that would destroy a whole region or a whole continent,鈥� says Ian Carnelli at the European Space Agency (ESA).
The past decade has also seen a massive effort to catalogue smaller asteroids, down to those around 100 metres in diameter. 鈥淎 100-metre asteroid would kill somebody, will create casualties, regardless of the entry point on the planet,鈥� says Carnelli.
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But for asteroids at around 1 metre or below, as 2024 RW1 was, tracking them all is probably an impossible task. 鈥淚f you go down to 1 metre, there are hundreds of millions of asteroids in the solar system, maybe even a billion,鈥� says Carnelli. That is OK though, as such small rocks pose no threat to Earth and simply burn up in the atmosphere, as 2024 RW1 did. 鈥淭here is only a scientific interest, but there鈥檚 no planetary defence interest,鈥� says Carnelli.
Because of this, Carnelli says it is likely that we will stop trying to comprehensively track asteroids once we have identified all that are above around 30 to 50 metres, slightly larger than the asteroid that struck near Chelyabinsk, Russia, in 2013.聽
Both NASA and ESA now have dedicated programmes for spotting and tracking asteroids, and they are working on ways to deflect those found to pose a risk. These programmes involve a large network of dedicated observatories, existing and new, as well as amateur astronomers who take readings of the positions of known objects so that their orbits can be better understood and predicted. Europe is building its Near Earth Object Survey Telescope, which Carnelli says will scour the sky for 鈥渋mminent impactors鈥� that don鈥檛 represent an existential risk to humanity, but could cause injuries.
鈥淭he main purpose is to avoid situations like Chelyabinsk, where you have an object exploding in the atmosphere, breaking windows,鈥� says Carnelli. While the chances of death from such an event are smaller, he says, there is a serious risk of injury if it were to happen again. 鈥淧eople went to see the light, the flash of light at the window, and then the shock wave arrives [and] shatters the window. You get injured, and [that] injury can be serious. So as a minimum, we want to be able to inform the population that something is coming.鈥�
Carnelli is also involved in efforts to hone our active asteroid defences. He is project manager of ESA鈥檚 Hera mission, which is designed to study the aftermath of a previous NASA mission that smashed into an asteroid in an attempt to change its orbit. Hera will launch next month to verify the results of the impact up close, and further improve our understanding of planetary defence.聽鈥淲e have developed, and we are developing, real planetary defence systems,鈥� says Carnelli.
