International Asteroid Day: Are we ready if an asteroid threatens Earth?

By Ashley Strickland

Published June 29, 2018

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, and exploded in the air. More than 1,000 people were injured, and the shock wave broke windows 58 miles away. It went undetected because the asteroid came from the same direction and path as the sun.


NASA and other space organizations around the world are focused on detecting the threat of near-Earth objects, or NEOs, asteroids and comets whose orbits place them within 30 million miles of Earth.

C. Veillet/Large Binocular Telescope Observatory

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.


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.


The goals 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.


We’ve mapped less than 1% of NEOs smaller than a kilometer. 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 every 10 to 100 years. "We will definitely see something like that again in our lifetime," Koshcny said.


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."


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.


In the United States, NASA's Planetary Defense Coordination Office is tasked with providing quick and accurate communication about potentially hazardous objects. The new US action plan includes efforts by NASA and FEMA to streamline communicating the risk of an approaching asteroid to the public, establishing evacuations in possible areas of impact and other emergency scenarios when we have only a few days' or months' notice.

Marc Serota/Getty Images

Two telescopes continually scan the night sky to detect any objects that are bright enough, which works well for large objects, but smaller objects can't be detected until they are as close as the moon, Koschny said.

D. Jewitt/ESA/NASA

"If you only have two of these telescopes on the planet and it takes each telescope three weeks or so to cover the complete sky, you have to be really lucky that a small asteroid crosses your field of view just when you're looking in the right direction," Koschny said. "That's why we are currently developing extremely wide-field telescopes that will have the ability to scan the entire sky in just 48 hours."

ESA 2010 MPS for OSIRIS Team via Getty Images

We also need to be able to find smaller NEOs on their final approach, days or weeks in advance, and be able to implement civil defense -- whether that be an evacuation or shelter in place, said Mark Boslough, professor of Earth and planetary sciences at the University of New Mexico and chairman of the Asteroid Day expert panel.

In the case of events like Chelyabinsk, which involve small asteroids that explode in the air, it's about increasing awareness of what not to do.

"We need to make sure that people understand if there is a large, unannounced air burst, don't go to the windows or look outside at the bright flash in the sky," Boslough said.

Barend Swanepoel/Vicus Van Zyl