Most of the asteroids capable of causing globally catastrophic disasters have been detected
Smaller asteroids, which can still cause significant damage, are harder to track
Saturday is International Asteroid Day, commemorating the Earth’s largest recorded asteroid impact while focusing on the real danger of asteroids that could collide with Earth.
In 1908, a powerful asteroid struck the Podkamennaya Tunguska River in a remote Siberian forest of Russia. The event leveled trees and destroyed forests across 770 square miles, which is equal to the size of three-quarters of the US state of Rhode Island. The impact threw people to the ground in a town 40 miles away.
Five years ago, an asteroid entered Earth’s atmosphere over Chelyabinsk, Russia. It exploded in the air, releasing 20 to 30 times more energy than that of the first atomic bombs, generating brightness greater than the sun, exuding heat, damaging more than 7,000 buildings and injuring more than 1,000 people.
The shock wave broke windows 58 miles away. It went undetected because the asteroid came from the same direction and path as the sun.
And it explains why astronomers and the Asteroid Day group want people to be aware. According to a recent Pew survey, 62% of adults in the United States think that one of NASA’s top priorities should be monitoring asteroids or objects that could hit Earth.
NASA and other space organizations around the world are focused on detecting the threat of near-Earth objects, or NEOs. Near-Earth objects are asteroids and comets whose orbits place them within 30 million miles of Earth.
Tthere are no known NEOs that post a significant threat, NASA announced last week. NASA’s NEO program funds and relies on detection and tracking efforts from observatories across the US and in space and collaborates with other observatories around the world.
According to Dante Lauretta, principal investigator on NASA’s OSIRIS-Rex mission, asteroids hit Earth every day. Most of them are so small that they burn up in the atmosphere. But small asteroids can still do damage, especially if they explode in the air over a city like in Chelyabinsk. And the smaller they are, the harder asteroids are to detect.
But new technology and planetary defense plans could change that.
An asteroid action plan
Last week, the US National Science and Technology Council released the National Near-Earth Object Preparedness Strategy and Action Plan that coordinates efforts over the next 10 years among NASA, the Office of Science and Technology Policy and FEMA. This plan acts on a strategy that was first laid out by the US government in 2016.
The goals of the plan include enhancing NEO detection, tracking and identification, improving prediction modeling, developing technology to deflect and disrupt NEOs, increasing international cooperation to prepare for NEOs and establishing emergency and action protocols in the event of impact.
The damage an asteroid can inflict depends on its size. The one that killed the dinosaurs was 15 kilometers (9.3 miles) across. Scientists have mapped 90% of the asteroids that are a kilometer in size or larger and know that they won’t pose a threat, said Detlef Koschny, head of the near-Earth objects team at the European Space Agency.
But we’ve detected and mapped less than 1% of NEOs smaller than a kilometer. The smaller the asteroid, the more likelihood of it impacting Earth. According to Koschny, 100-meter asteroids strike every 10,000 years and 50-meter asteroids every 1,000 years.
Asteroids that are about 20 meters, like the one in Chelyabinsk, occur on average once every 10 to 100 years. “We will definitely see something like that again in our lifetime,” Koshcny said.
Per the new report, NASA will be looking for asteroids that are as small as 50 meters across. Previously, it focused on larger ones, 100 meters across and bigger, because they have the ability to affect entire regions and continents. But asteroids smaller than 50 meters across can also inflict significant damage. There are 10 million NEOs larger than 20 meters and 300,000 objects larger than 40 meters that could pose an impact hazard, according to NASA, but they are hard to detect more than a few days in advance.
The Asteroid Institute is also partnering with Google Cloud and Analytical Graphics Inc. to keep track of asteroid discoveries using a cloud-based platform for the Asteroid Decision Analysis and Mapping project.
This was designed because in a few years, the Large Synoptic Survey Telescope will come online and enable the discovery of tens of thousands of asteroids in orbits that could bring them closer to Earth, said Ed Lu, executive director of the Asteroid Institute and a former NASA astronaut.
“There is about to be an awful lot more data and observations on asteroids,” Lu said. “We’re preparing for this flood of data. Together with our partners, we are working to understand how well we are going to be able to determine if an asteroid is going to hit the Earth. More observations means less uncertainty.”
In 2005, Congress tasked NASA with finding at least 90% of NEOs that are at least 140 meters in size by 2020. Since then, the overall number of cataloged NEOs has increased by five times, but current capabilities and estimates suggest that we can find less than half of those objects by 2033. This is why the new plan focuses on enhancing NEO detection and pushing those capabilities forward.
There are multiple missions planned and in progress that will aim to study asteroids as well as deflect them.
NASA’s OSIRIS-REx space probe will spend two years flying through space to catch up to an asteroid named Bennu, a big, roundish space rock that has made it onto NASA’s list of potentially hazardous asteroids. That means Bennu is one of the most dangerous space rocks we know of because it could one day collide with Earth. It launched in September 2016 and will reach Bennu at the end of this year to study the asteroid’s composition.
On Wednesday, Japanese spacecraft Hayabusa2 reached the diamond-shaped asteroid Ryugu three years after setting off on its mission.
The spacecraft is 12.4 miles from the asteroid, from where it will launch a projectile into the rock in a bid to excavate samples from beneath the surface. Later, Hayabusa2 will touch down on the asteroid and collect the samples. It will depart Ryugu in December 2019 and finally return to Earth by the end of 2020.
The Double Asteroid Redirection Test, or DART, launching in the early 2020s, will rendezvous with the near-Earth asteroid Didymos. Though Didymos is 800 meters across, it has a secondary body, or a moonlet, that is 150 meters across and closer in size to an NEO hazard. DART will crash into the asteroid, changing the speed of the moonlet. Spacecraft that can change the orbit or path of an NEO could be used to defend Earth from bigger asteroids.
“DART would be NASA’s first mission to demonstrate what’s known as the kinetic impactor technique – striking the asteroid to shift its orbit – to defend against a potential future asteroid impact,” said Lindley Johnson, NASA’s planetary defense officer in Washington, in a news release. “This approval step advances the project toward an historic test with a non-threatening small asteroid.”
NASA’s Asteroid Redirect Mission was designed to develop a robotic spacecraft that would collect a multiton boulder from the surface of an NEO and redirect that boulder into orbit around the moon, proving that we can change the orbit of an NEO on a less-threatening path. But the mission was canceled at the end of 2017.
The new plan suggests developing deflection and disruption missions, like gravity tractors, kinetic impactors (like DART) and even a nuclear explosive device that could break asteroids of a certain size into smaller pieces that would disintegrate.
This may sound like doomsday preparation from “Deep Impact” or “Armageddon,” but the asteroids they’re intended for probably wouldn’t cause the end of all humanity.
What if an asteroid strikes Earth?
NASA estimates that we need 10 years’ notice to properly prepare for an asteroid on a collision course with Earth. The more asteroids we catalog, the better chance we have at tracking them and mitigating the risk with such a large time frame.
And should we have 10 years’ notice, sophisticated plans need to be in place and communicated globally.
“If there needs to be an evacuation, where do you evacuate to?” asked Debbie Lewis, a specialist in asteroid risk management and communications. “Rather than a tented village scenario, I