How a Small Asteroid Strike Could Save Earthlings from City-Killing Space Rocks
Movies that imagine an asteroid or comet catastrophically hitting Earth always feature an important scene: a lone astronomer hurtling the wrong space segment toward us, causing panic and a growing sense of existential dread. As the researcher tells the wider world.
On March 11, life began to imitate art. That evening, at the Concoli Observatory’s Pizzestetto Mountain station near Budapest, Krzysztyn Cranzewski was looking at the stars. Unsatisfied with the discovery of 63 near-Earth asteroids throughout his career, he set out to find his 64th – and he succeeded.
At first what he saw appeared normal. “It was not unusually fast,” said Mr. Sarnezki. “It wasn’t unusually bright.” Half an hour later, he observed “It was speeding up. That’s when I realized it was fast approaching us.”
It may have sounded like the beginning of a melodramatic disaster movie, but the asteroid was just six feet tall—a dreaded Pipsak. And Mr. Sernezky felt delighted.
“I have dreamed of such a discovery many times, but it seemed impossible,” he said.
Not only did he spy a new asteroid, he also detected one just before it collided with planet Earth, only the fifth time such a discovery has been made. The object, later named 2022 EB5, may have been harmless, but it turned out to be a fine test of equipment designed by NASA to protect our planet and its inhabitants from a collision with a more dangerous rock from space.
One such system, Scout, is software that uses astronomers’ observations of near-Earth objects to determine where and when their impacts may occur. Within an hour of the 2022 EB5 detection, Mr. Sarnezki shared his data and it was rapidly analyzed by Scout. Even though 2022 EB5 was due to hit Earth just two hours after its discovery, the software managed to calculate that it would enter the atmosphere off the east coast of Greenland. And at 5:23 p.m. Eastern Time on March 11, he did just that, blasting into the air.
“It was an amazing hour and a half in my life,” said Mr. Sarnezki.
Although EB5 was low, it doesn’t take a big leap in size for an asteroid to become a threat. For example, in 2013 a 55-foot cliff exploded above the Russian city of Chelyabinsk, detonating the equivalent of 470 kilotons of TNT, breaking thousands of windows and injuring 1,200 people. That scout can accurately plot a small asteroid’s trajectory which provides a form of reassurance. If seen long enough, a city facing a future Chelyabinsk-like space rock could at least be warned.
It usually takes a few days of observation to confirm the existence and identity of a new asteroid. But if that object turns out to be a small-but-dangerous space rock that was about to hit Earth, the decision to wait on that additional data first could have disastrous consequences. “That’s why we developed the Scout,” said David Farnochia, a navigation engineer at the Jet Propulsion Laboratory who developed the program, which went live in 2017.
The scout continually looks at data posted by a clearinghouse at the Minor Planet Center, Cambridge, Mass., which notes the discoveries and positions of small space objects. The software then tries to “figure out if something is headed toward Earth,” Dr. Farnochia said.
That Mr. Sarnezki was the first in 2022 EB5 came down to both skill and luck: he’s a veteran asteroid hunter who was seriously on the right side of the globe to spot the object on his Earth journey. And his efficiency allowed the Scout to kick into gear. Within the first hour of making his observations, Mr. Sarnezky processed his images, double-checked the object’s coordinates, and sent everything to the Minor Planet Center.
Using 14 observations taken over 40 minutes by a single astronomer, the scout correctly predicted the time and location of 2022 EB5’s encounter with Earth’s atmosphere. There was no one around to see it, but there was a weather satellite recorded his last moment: A short-lived flame that consumes quickly at night.
This is not Scout’s first successful prediction. In 2018, another small Earthbound asteroid was discovered 8.5 hours before impact. The scout pinpointed its trajectory correctly, which proved crucial to meteorite hunters, who found the two dozen remaining fragments in the lion-filled Central Kalahari Game Reserve in Botswana.
This will not be possible for 2022 EB5.
“Unfortunately, it landed in the ocean north of Iceland, so we won’t be able to recover the meteorites,” said Paul Chodas, director of the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory.
Dr. Chodas said that we should not even worry that this asteroid was detected two hours before its arrival.
“Small asteroids for this size impact Earth quite often, more than once a year,” he said. And their size means that their effects are usually without consequence. “Don’t sweat the small things,” said Dr. Chodas.
That scout continues to demonstrate his ability, he is welcome. But it will be of little comfort if this program, or NASA’s other near-Earth object monitoring system, identifies a very large asteroid coming our way, as Earth currently lacks ways to defend itself.
A global effort is underway to change this. Scientists are studying how nuclear weapons can bend or destroy dangerous space rocks. And later this year, the Double Asteroid Redirect Test, a NASA space mission, will slam into an asteroid in an attempt to change its orbit around the Sun — a dry run for the day when we should see an asteroid out of Earth’s path. Knocking is required. Real.
But such efforts would be of no use if we remained ignorant of the locations of potentially dangerous asteroids. And in this regard, there are still much more known unknowns.
Although scientists suspect that most of the near-Earth asteroids that caused worldwide devastation have been identified, a handful may still be hidden behind the Sun.
The more related near-Earth asteroids are about 460 feet across, numbering in the thousands. They can cause city-level explosions “larger than any nuclear test”, said Megan Brooke SyalA planetary defense researcher at Lawrence Livermore National Laboratory. And astronomers estimate that they have currently discovered about half of them.
Even an asteroid just 160 feet long hitting Earth is “still having a really bad day,” said Dr. Brooke Syall. One such rock erupted over Siberia in 1908, flattening 800 square miles of forest. “That’s still 1,000 times more energy than the Hiroshima explosion.” And perhaps only 9 percent of near-Earth objects have been observed in this size range.
Fortunately, in the coming years, two new telescopes could help with this task: the giant optical Vera C. Rubin Observatory, and the space-based Infrared Near-Earth Object Surveyor Observatory. Both are sensitive enough to potentially find 90 percent of those 460-foot or larger city killers. “As good as our capacity is right now, we need these next generation surveys,” Dr. Chodas said.
Hope time is on our side. The odds that a city-destroying asteroid will hit Earth are about 1 percent per century—low, but not comfortably low.
“We don’t know when the next impact will happen,” Dr. Chodas said. Will our planetary defense system be fully operational before that dark day arrives?
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