In the next decade, NASA and the European Space Agency will launch missions to protect Earth from disastrous asteroid impacts – until then, we’re basically blind
An asteroid slamming into Earth is a classic extinction scenario – just look what it did to the dinosaurs – but, in 2023, there are plenty of measures to ensure it doesn’t actually come true. Artificial intelligence, for example, has already been set to work on identifying “potentially hazardous” asteroids hurtling through space, and last year NASA successfully bumped an asteroid off course with a spacecraft, in a first-of-its-kind experiment. But are we completely safe?
Unfortunately, the answer is no, at least according to scientists at NASA. Why? Well, there are some space rocks that we just can’t see coming, because they’re hiding behind the sun’s glare. One such asteroid – a 1.5-kilometre-wide “planet killer” dubbed 2022 AP7 – was found just last year after a rare crossing of Earth’s orbit. Another went undiscovered until it exploded miles over Chelyabinsk, Russia, in 2013, temporarily blinding onlookers and shattering thousands of windows. Luckily no one was killed.
It’s quite rare for an asteroid of this size to make it to Earth without some forewarning. The European Space Agency estimates that rocks the size of the Chelyabinsk meteor only strike once every 50 to 100 years. In fact, space agencies have already mapped tens of thousands of near-Earth space rocks, and none of them are on a collision course for at least another century. The fact that such asteroids can pop out from the sun’s glare without warning, though, raises an unnerving question: what about the ones we can’t see?
The “invisible” asteroids that are hidden from our telescopes by the sun’s blinding light could number in their thousands, experts recently told Live Science. These could range in size from a few feet across (asteroids like this hit Earth about once a fortnight), to “city killers” more than 140 in diameter, or one-kilometre-across “planet killers”, which would cause widespread destruction and even extinction-level events.
The most dangerous group of these asteroids, according to the scientists, are called “Atens”. As Aten asteroids orbit the sun, they mostly stay within the bounds of Earth’s orbit, meaning that they’re always facing the side of the planet that’s bathed in daylight, making them near-impossible to spot. The problem is, that they can cross Earth’s orbit “just barely” during their flightpath. This is when they could potentially strike. “You would never see one coming, to some degree,” Scott Sheppard, a staff scientist at the Carnegie Institution for Science, tells Live Science, “because they’re never in the darkness of the night sky.”
Other scientists have raised concerns about unseen asteroids, but they’ve been working to limit the potential disasters as well. Around 2030, for example, ESA is set launch an orbiting observatory as part of its NEOMIR mission, which will be equipped with tall solar shades and infrared detectors, scanning an area around the sun for near-Earth objects. According to theoretical calculations, it would have seen the Chelyabinsk meteor about a week in advance, giving people time to prepare or make necessary evacuations.
Before NEOMIR, in 2027, NASA is also scheduled to launch its NEO (or Near-Earth Object) Surveyor, an infrared space telescope specifically designed to help planetary defence efforts. Over five years this will perform a survey of the sky, with an aim to find at least two-thirds of the near-Earth objects larger than 140 metres, taking measurements of their size, shape, and orbits.
Both telescopes will unlock the ability to spot many more asteroids by turning their gaze closer to the sun than ever before, and using their infrared imaging to identify asteroids from their thermal emissions, which – as in the famous case of Bennu – cause them to emit a glow that’s imperceptible to the human eye. Hopefully, this will significantly reduce the dangers of space-rock collisions in the future. Until then? We’ll just have to pray!