Asteroid 2019 AX8 made a close approach to Earth Monday night, skimming past our planet at 10:35 pm Eastern standard time. Discovered just two weeks ago, AX8 was last tracked by NASA on January 11. The asteroid missed Earth by a distance of roughly 6.9 million kilometers (4.3 million miles) – around 18 times further away than our Moon. This may seem like a significant distance, but it is relatively close in astronomical terms
With a diameter between 28 and 63 meters (92 to 207 feet) across, Asteroid AX8 could have done some serious damage if the body had struck the planet. To put its size into perspective, AX8 is roughly half the height of the Great Pyramid of Giza.
“We’re developing a lot of technologies for operating with precision around these kinds of bodies, and targeting locations on their surfaces, as well as characterizing their overall physical and chemical properties. You would need this information if you wanted to design an asteroid deflection mission,” said Dante Lauretta, from the University of Arizona in Tucson, principal investigator for the OSIRIS-REx project.
Were a large asteroid seen headed toward Earth, there are options engineers could take to divert disaster. Despite all the movies from Hollywood centered around the idea of blasting an incoming body to smithereens (usually using nuclear weapons), this would likely be a terrible idea. Such an effort would only break a single object into thousands of smaller objects, devastating vast areas of our planet.
Changing the course of an asteroid would be the first option, and NASA is planning to test systems to do exactly that. In 2022, the space agency (in cooperation with the European Space Agency) is planning to launch the Double Asteroid Redirection Test (DART), the first-ever attempt to knock an asteroid off its usual orbit.
The DART mission will head toward Didymos B, an asteroid roughly 160 meters (530 feet) in diameter, which orbits another asteroid almost five times its size, called Didymos A. The plan is for DART to collide with the smaller body at a velocity of six kilometers (3.7 miles) per second, hopefully changing the orbit of Didymos B by 0.4 millimeters (1/100th inch) per second. This change in velocity is small, but will be enough to be recorded by telescopes. Soon after impact, the HERA spacecraft from ESA will arrive at the pair, along with two small CubeSats which will land on the bodies.
“A binary asteroid is the perfect natural laboratory for this test. The fact that Didymos B is in orbit around Didymos A makes it easier to see the results of the impact, and ensures that the experiment doesn’t change the orbit of the pair around the sun,” said Tom Statler, program scientist for DART at NASA.
Thousands of asteroids enter the atmosphere of the Earth every day, but most burn up harmlessly before ever reaching the ground, creating “shooting stars.” On February 15 2013, a meteor roughly half the size of AX8 exploded over Chelyabinsk, Russia, injuring more than 1,100 people, and damaging 7,000 buildings.