Don’t panic, but an asteroid dubbed 2017 AG13 passed within half the distance to the Moon last week while you were enjoying your morning coffee. This large asteroid was discovered on January 7th by the University of Arizona’s Catalina Sky Survey. 2017 AG13 was moving at 16 kilometers per second when it passed Earth at 7:47 AM Eastern time on January 9 and is expected to cross Venus’ orbit.
Risks Posed By Near Earth Objects
Asteroids like 2017 AG13 are referred to as Near Earth Objects (NEOs) because their orbits around the sun bring them close to Earth orbit on a regular basis. If they reach Earth’s orbit at the right time and place, they could enter Earth’s atmosphere.
If 2017 AG13 had entered the atmosphere, it would likely have exploded as an airburst with a force of 700 kilotons of energy. It wouldn’t have done much more than startle some people with a loud boom because it would have happened far up in the atmosphere.
However, this does not mean that NEOs cannot cause damage if they are big enough to survive a trip through Earth’s atmosphere. A large asteroid is believed to have contributed to the extinction of the dinosaurs. The meteor that exploded over Chelyabinsk, Kazakhstan, in 2013 shattered windows, caused minor damage to buildings, and injured 1,500 people.
Searching for Near Earth Objects
Proposals for finding potentially dangerous NEOs include the Near-Earth Objects Camera, or NEOCam. The NEOCam would use the infrared spectrum to search for NEOs with a diameter of at least 140 kilometers, which is large enough to pose a potential threat to Earth. This camera would be able to detect up to 10 times more large NEOs than have been discovered to date. However, NEOCam has not yet been fully funded by NASA.
On the plus side, NASA has recently announced plans to better coordinate efforts to identify potentially hazardous NEOs and mitigate the hazards by creating the Planetary Defense Coordination Office. Current NASA-operated NEO detectors include the space-based infrared telescope NEOWISE, the Hawaiian telescope Pan-STARRS, the Infrared Telescope Facility and the Spitzer Space Telescope. The orbits of known NEO asteroids are currently predicted and monitored by JPL’s Center for NEO Studies (CNEOS).
Will It Be Enough?
As we’ve seen with unexpected close encounters like 2017 AG13, it’s possible for a large NEO asteroid to surprise us. This becomes a risk when we cannot predict when a dangerously large asteroid might strike Earth or where the worst impact zone will be. Advance warning may give a likely impact zone time to evacuate and give federal emergency relief agencies like FEMA time to prepare emergency responses.
Enough advance warning may also give us time to avoid a collision altogether. Proposed methods for deflecting an asteroid include sending a robotic spacecraft to give the asteroid enough of a nudge to alter its orbit just enough so that it will miss Earth. Variations of this plan include sending a spacecraft to paint the asteroid a bright enough color that it will reflect the sun’s rays or attach a solar sail to the asteroid in an attempt to deflect its path using the pressure of the solar wind. This presumes that asteroid hunters will detect the NEO soon enough for the effort to make a difference.
Even If No Asteroid Hits, Detecting Them Is Not A Bad Thing
Besides the fact that future asteroid mining corporations may be interested, we’ll at least know that the NEOs are there even when they aren’t an immediate threat. 2017 AG13 would have made a good attention-getter by making a loud noise if it had entered Earth’s atmosphere. However, it was already past before it was spotted. Which asteroid will be next to make a close flyby of Earth, and will we see it before that happens?