Its Hayabusa spacecraft landed on Itokawa, a near-Earth asteroid, in 2005. Although it faced a number of technical troubles over the course of its mission, it managed to return a canister to Earth in 2010 that contained less than a milligram of particles from the asteroid. Scientists have used the samples for a variety of scientific research, arguing in a study last year, for instance, that asteroids that formed closer to the sun may have been a source of Earth’s water.
But that mission was less elaborate than Japan’s follow-up spacecraft, Hayabusa2.
It met up with another asteroid, Ryugu, in 2018 and conducted months of more successful scientific observations on and around the asteroid. It dropped small robotic explorers on the asteroid, attempted a sample collection and even used an explosive device to blast a crater on its surface. It tried to collect more debris from that crater, hoping to study parts of the asteroid that haven’t been weathered by eons of time in space.
Hayabusa2 is currently traveling back to Earth, and will drop off its sample canister in Australia’s outback on Dec. 6. Japan’s space agency recently decided to extend the spacecraft’s mission, sending it to explore another target in the solar system that has not yet been selected.
What other asteroids will be visited by spacecraft from Earth soon?
NASA has three other upcoming asteroid missions.
The Double Asteroid Redirection Test mission, or DART, will be the first test of technology that could be used to divert an asteroid that is discovered to be on a collision course with Earth. Despite what is depicted in movies such as “Armageddon,” scientists generally believe blowing up an asteroid would fail if most of the smaller pieces still collide with Earth.
DART will slam into a moon orbiting a larger asteroid, and scientists will be able to measure how much the orbit of the asteroid moon changes. (There are no asteroids known to pose any danger to Earth this century, but not all asteroids have been found yet.)
Another mission, Lucy, is scheduled to launch next year. It will fly past a series of objects known as the Trojan asteroids, which are gravitationally trapped in Jupiter’s orbit.
“The Trojans, despite the fact that they’re in a very narrow region of space, are very different from one another,” said Harold F. Levison, the principal investigator of the Lucy mission. “They have different colors, different spectrum. And that probably means that they formed in very different regions of the solar system.”