A large asteroid has been observed in space before hitting Earth. It’s the fifth known impactor to be detected before it hits the ground and the first from Europe. Signals from the impact in Iceland and Greenland were recorded and indicated an energy release comparable to a magnitude 4.0 earthquake. All five asteroids that were spotted before impact were found after 2008, demonstrating how far asteroid detection technology has progressed in recent years.
The majority of asteroids that have collided with Earth were detected many years, if not millions, after the occurrence. The proof? Around 200 documented craters scar the Earth’s surface, providing a powerful tale about how catastrophic impacts with ancient space objects have radically impacted our planet and life on it. We seldom find an asteroid before it impacts — five times in human history, to be exact.
Warning of certain impact
Using the 60cm Schmidt telescope at the Piszkésteto observatory in Hungary, astronomer Krisztián Sárneczky found a bright and fast-moving new object in the sky at 19:24 UTC on March 11, 2022. He made four observations in short succession and transmitted his results to the Minor Planet Center (MPC) 14 minutes later, originally naming the object ‘Sar2593.’
The findings were immediately published and utilized by automated impact assessment systems all across the globe to determine the likelihood of an effect: it looked improbable at the time, with a probability of less than 1%.
Krisztián continued to watch the object following its discovery, making a total of 10 observations and sending them to the MPC. These, on the other hand, resulted in a very different situation. Based on the cumulative observations, ESA’s “Meerkat” monitoring system prompted an alarm to the Agency’s Near-Earth Object Coordination Centre (NEOCC) almost precisely an hour after it was spotted at 20:25 UTC.
The probability of an impact had increased to 100 percent, and it would occur in less than an hour, between 21:21 and 21:25 UTC. The impact site of the new item was already predictable to the nearest thousand kilometers and was projected to be only a few hundred kilometers north of Iceland.
Rapid response to a speedy space rock
In response to ESA’s Meerkat alert and others like it, professional and amateur observers across Europe and Asia quickly started to observe the imminent impactor. Finding it was extremely challenging since the object was already very close (about 1/7th the distance to the Moon) and moving rapidly in the sky.
Another observatory – Kysuce, Slovakia – soon reported its successful observations, together with many more detections from the original discoverer. With this new data added to the mix, the location of the asteroid impact could be pinpointed even more precisely: the asteroid was going to enter the upper layers of our atmosphere roughly 140 km south of the Jan Mayen island at 21:22:42 UTC – less than two hours after being discovered.
From its observed brightness, the object appeared to be very small. At roughly a meter in diameter it posed no threat to Earth, as at this size it would entirely burn up in Earth’s atmosphere.
Shortly after the expected time of impact the Minor Planet Center designated the asteroid the title “2022 EB5,” becoming just the fifth known impactor observed in space before hitting our planet, and the first discovered from Europe.
Unfortunately, no conclusive visual or video detections of the corresponding fireball have been located at present, likely due to the remoteness of the impact location.
Nevertheless, there is independent evidence that the impact did in fact occur thanks to the international network of infrasound detectors. Signals from the impact were detected from Iceland and Greenland, suggesting an energy release equivalent to roughly a magnitude 4.0 earthquake.
Why only the fifth?
It is estimated that between 40 and 100 tonnes of space material strike Earth every day, most in the form of very small particles. Larger objects, similar in size to 2022 EB5 are expected to strike roughly ten times per year. So why have only five asteroids been detected before impact?
The news here is rather positive. Large asteroids, kilometers in diameter, are easier to spot. Although they could do immense damage, they are thankfully relatively rare. We now know where the vast majority of these are and can say for certain that they are safe, at least for the next hundred years. The international community continues to seek out every last one.
Smaller asteroids are far more common and strike Earth much more frequently, but their impact is small and they’re much harder to spot. All five asteroids, spotted before impact, were found since 2008, illustrating how much asteroid observation technologies have improved in the last years.
Many more to come
More dedicated sky scanning telescopes are in the pipeline, including ESA’s first state-of-the-art Flyeye telescope soon to be constructed in Monte Mufara, Italy. The new, European telescope will split each image into 16 smaller subimages, expanding its overall field of view – similar to the technique exploited by a fly’s compound eye.
“The extremely wide field of the new telescopes will allow us to cover a large area of the sky in just one night,” says Detlef Koschny, ESA’s acting Head of Planetary Defence.
“This will reduce the chance that we miss any interesting object.”
As our ability to predict asteroid impacts improves, so will our preparation. For medium-sized impacts that can create airbursts in the sky, this means the chance to warn people to stay away from windows that could break in the explosion. For larger objects, this means having the chance to prepare asteroid deflection missions to prevent impact altogether.
For more on this story, see Small Asteroid Strikes Earth’s Atmosphere – Discovered Just Two Hours Before Impact.