City-killing asteroid won't hit Earth in 2052 after all

ESA ruins our day with some bad news

An asteroid predicted to hit Earth in 2052 has, for now, been removed from the European Space Agency's list of rocks to be worried about.

Asteroid 2021 QM1 was described by ESA as "the riskiest asteroid known to humankind," at least among asteroids discovered in the past year. QM1 was spotted in August 2021 by Arizona-based Mount Lemmon observatory, and additional observations only made its path appear more threatening.

"We could see its future paths around the Sun, and in 2052 it could come dangerously close to Earth. The more the asteroid was observed, the greater that risk became," said ESA Head of Planetary Defense Richard Moissl. 

Observations of QM1 were interrupted when it was blocked out by the Sun. When it finally emerged from behind our star in late May, QM1 was the faintest asteroid ever observed, though ESA scientists still managed to spot and track it. And so it seems it won't hit Earth in 2052 after all.

"With these new observations, our risky asteroid's path was refined, ruling out an impact in 2052, and 2021 QM1 was removed from ESA's risk list," the agency said today. It noted that 1,377 asteroids remain on the sheet.

Estimated to be between 37 and 82 metres across (121 to 269 feet), QM1's size puts it solidly in NASA's "dangerous" category: "If a rocky meteoroid larger than 25 metres but smaller than one kilometre were to hit Earth, it would likely cause local damage to the impact area," the US agency said. Rocks larger than a kilometre or two could have a worldwide impact, according to the Americans.

One such larger asteroid was discovered in 2013 by Russia's space agency, and is being observed as it may hit in 2032. NASA said it's unlikely to crash into us. If it does, the rock would strike with an equivalent of 2,500 megatons of explosives, many times greater than the largest nuclear device ever detonated, the 50MT Soviet Tsar Bomba.

Still, asteroids with the explosive force of sub-megaton nuclear bombs hit Earth on average twice a year, a study from NASA astronaut-founded B612 Foundation concluded. Dr Ed Lu, the foundation's CEO and a former shuttle pilot, said fewer than 10,000 of more than a million asteroids with the potential to destroy a major metropolitan area have been identified.

Smaller space rocks are a risk, such as the one that exploded some 30 or more kilometres above the ground over the Russian city of Chelyabinsk in 2013. The 20-metre-wide, 10,000-ton meteor caused windows to shatter and damage to buildings, leading to more than 1,100 injuries and elevating asteroid strike fears.

As for QM1, it's off the threat list just in time for this year's Asteroid Day on June 30, though it might not remain that way. "We can safely say that the riskiest asteroid known to humankind in the last year will not strike – at least not for the next century," ESA said. ®