An asteroid the size of a small refrigeratornearly collided with Earth on October 24th, and no one knew it was there until it was already gone.
DubbedAsteroid 2021 UA1, the hefty piece of space rock hurled over Antarctica at a distance of only 1,800 miles. For comparison, that is about five times the altitude of the International Space Station, but significantly closer than the ring of geostationary communications satellites that sit well over 20,000 miles above Earth. Bottom line, this was a close call with a pretty big rock.
BACKGROUND: OTHER SPACE ROCK NEAR MISSES
Asteroids that come much closer to Earth usually burn up in the atmosphere. For example, a bolide estimated to be twenty times as large as 2021 UA1 ripped through the atmosphere over the town of Chelyabinsk, Russiaback in 2013 before exploding with enough power to blast out windows all over town. According to reports, only a small boulder remained.
The most recent occurrence of an asteroid coming this close to slamming into Earth without actually entering our atmosphere occurred just last November, whenNASA’s Atlas Project spotted a rock named 2020 VT4 whipping by at nearly the same altitude as the ISS.
ANALYSIS: HOW did WE MISS THIS ASTEROID?
Astronomers say they missed asteroid 2021 UA1 because it approached from the direction of the sun. The same issue masked the approach of the Chelyabinsk rock back in 2013, highlighting one of many issues faced by folks trying to protect the planet from incoming space rocks.
“The fact that the three closest passes ever observed have all come in the last 18 months isn’t anything to lose sleep over,” saysa report from Cnet.com. “It doesn’t mean asteroids are swarming Earth; actually, it reflects improvements in sky surveying technology and astronomers’ ability to spot and track more near-Earth objects. If anything, more known asteroids should allow us to rest easier at night.”
OUTLOOK: NASA, DART, AND THE FUTURE OF PLANETARY PROTECTION
In an attempt to protect Earth from the seemingly inevitable collision with a large space rock, perhaps big enough to cause a worldwide extinction event,NASA is preparing to launch the DART mission on November 23rd of this year. Designed as a proof of concept mission, DART will track down a small moonlet asteroid named Dimorphos and intentionally crash into the space rock. If all goes well, the test will provide critical data on current capabilities to change the orbit, and ultimately the trajectory, of an incoming rock. That is, as long as we see it coming first.