Scientists say asteroid discovery and strike is sign planetary defence systems are working

Small space rock exploded in fireball over Arctic sea earlier this month

Just hours after its incidental discovery earlier this month, a small asteroid exploded in a fireball over the Arctic sea.

But the short time between the discovery of the space rock known as 2022 EB5 and it hitting the Earth isn’t worrying scientists.

Asteroids of 2022 EB5’s size, around two to three metres diameter, don’t pose a threat to people on the ground, and the quick turnaround between spotting the asteroid and predicting its impact is a sign that planetary defense systems are working well.

“It shows that in a short time frame, we can collect enough data, we can compute the right trajectory and predict the right impact location,” said Davide Farnocchia, a navigation engineer at the Jet Propulsion Laboratory and the Center for Near Earth Object Studies, where he helps compute the trajectories of asteroids and comets in the Solar System.

“That’s really good news,” he said, and exactly what he would hope would happen in the case of a larger asteroid that did pose a risk to Earth; larger asteroids are easier to detect earlier, providing decision-makers with time to take action if a space rock threatens Earth.

And scientists have put a lot of effort into looking for asteroids that could pose a threat, especially since Nasa created its Planetary Defense Coordination Office in 2016, though the search for potentially hazardous objects has been going on since long before then.

In 2005, the US passed a law mandating that Nasa find, analyse and catalogue more than 90 per cent of asteroids measuring one kilometer in diameter or greater, the size at which a space rock poses a global risk to the Earth.

“That was the biggest risk and that goal has been achieved, we now have about 95 per cent of those objects in the catalog, and none of them represent any, any threat for the foreseeable future,” Dr Farnocchia said.

“The next goal is to reach the same 90 per cent for the objects greater than 140 meters, which are not necessarily going to cause global level devastation, but they could still cause significant damage.”

Multiple active search programs are looking for potential hazardous “near Earth objects,” including many funded by Nasa’s Planetary Defense Coordination Office, Dr Farnocchia says, but anyone pointing a telescope at the sky is a potential sentinel.

“They might be looking at galaxies or these kinds of things,” he said, “but they might happen to spot asteroids while they’re doing it.”

Observers report newly discovered candidate asteroids to the Minor Planet Center, which posts the initial information on a confirmation page, “where they put essentially all new candidate objects,” Dr Farnocchia said, “and they wait for enough data to make sure the object is real.”

On 11 March, Hungarian astronomer Krisztián Sárneczky made the first observation of what the Minor Planet Center would dub 2022 EB5, and based on the Minor Planet Center posting, amateur and professional astronomers trained their instruments on the candidate object to confirm Dr Sárneczky’s discovery.

The additional data was fed into special software at both the European Space Agency and Nasa, the Meerkat, and Scout systems, respectively.

“The Sort software picked up the data automatically, started crunching the numbers and figuring out the possible trajectories, projecting the object into the future to see whether it could hit [Earth],” Dr Fanoccchia said. “That probability was 100 per cent.”

An asteroid large enough to threaten Earth would be visible sooner than 2002 EB5 was, he said, so scientists knew it posed little threat. But in a situation where a larger asteroid threatened Earth, the next step would be to determine what mitigation efforts are appropriate.

“You might want to try to deflect it,” Dr Farnocchia said. “Or if the object is small enough, and there's no time for deflection, you might want to try and move people out of the way.”

Nasa is researching multiple approaches for deflecting hazards asteroids or comments, including using a spacecraft flying close to the object over time to slowly pull the object into a different orbit through mutual gravitational attraction, and using nuclear detonations or kinetic impacts to push the object off course.

Nasa’s 2005 Deep Impact mission successfully struck a comet with an impactor, primarily as means to study the comet’s interior, but Dr Farnocchia points to it as a proof of concept that a space mission can successfully strike a distant object.

And in September Nasa’s Double Asteroid Redirection Test, or DART, will slam a kinetic impactor into the minor planet Dimorphos attempt to change its orbit. Neither Dimorphos’s current orbit, if DART succeeds, its new orbit will bring it on a collision course with Earth.

Objects like 2022 EB5, meanwhile, strike Earth all of the time, “Maybe once a year or so on average,” Dr Farnocchia said, part of the 100 tonnes or so of material that strikes Earth every day.

But while it’s routine for smaller objects to strike the Earth, spotting them before they do so is not: 2022 EB5 is only the fifth such asteroid detected before striking our planet, the result of the better, broader network of observations rather than a lack of candidate asteroids.

“When you find them, that’s actually a very good exercise for the whole system,” Dr Farnocchia said. “Can you recognize the object is on an impact trajectory? And can you predict the impact location?”

In the case of 2022 EB5, automatic warning systems such as Meerkat and Scout worked perfectly, pinpointing nearly the exact location the space rock would burst in the air above the sea, near the Norwegian island of Jan Mayen.

“From my perspective, it was really impressive that we were able to turn things around in only two hours, two hours from first detection to impact,” Dr Farnocchia said. “Scout worked perfectly automatically. I was just babysitting things, but I didn't really have to touch anything and I was getting updated impact location estimates.”

Going forward, the quick turnaround from discovery to impact prediction for 2002 EB5 should reassure people, Dr Farnocchia said, and the knowledge that so many searches of the sky are ongoing, looking for hazardous and non-hazardous objects alike.

“Find them before they find us,” he said, “that’s the rule of the game.”