Japanese spacecraft successfully touches down on an asteroid, grabbing a sample of dust


FEBRUARY 22, 2019

Around 200 million miles away from Earth, a Japanese spacecraft just grabbed a tiny sample of dirt off the surface of an asteroid — the second time humanity has ever pulled off such a feat. The precious samples are destined to come back to Earth, where they’ll be analyzed by scientists. This scrutiny could tell us a great deal about the chemical makeup of these rocks, as well as what materials were present in the early days of the Solar System.

The spacecraft in possession of this newly acquired asteroid material is Hayabusa-2, operated by the Japan Aerospace Exploration Agency (JAXA). It’s the successor to JAXA’s original Hayabusa mission, which was the first to return samples of an asteroid to Earth in 2010. Launched in 2014, Hayabusa-2 traveled through space for three and a half years, arriving at an asteroid named Ryugu in June 2018. Ever since then, Hayabusa-2 has been hanging around Ryugu, analyzing its surface and practicing for today’s big sample grab.

Late last night, the spacecraft fired its engine, initiating the vehicle’s slow descent to Ryugu’s surface. Then, when Hayabusa was hovering just above the asteroid, it tapped a horn-like appendage onto the ground. As soon as that happened, a bullet-like projectile within the horn shot outward, stabbing the asteroid and creating a bunch of dust and fragments. If all went well, some of those fragments fed up into the horn and gathered inside a little chamber inside the spacecraft.

“These asteroids are the first rocks that formed around the Sun before the planets existed.”

Now, Hayabusa-2 will hold onto that material until it leaves Ryugu and returns to Earth. And when these samples arrive at our planet, they could tell us a bit more about what our cosmic neighborhood was like billions of years ago. “From a scientific perspective, it’s going back to the dawn of the solar system,” Dante Lauretta, the principal investigator for NASA’s asteroid sample return mission OSIRIS-REx, who has worked with the Hayabusa-2 team, tells The Verge. “These asteroids are the first rocks that formed around the Sun before the planets existed.”

Hayabusa-2 is hoping to bring back between 10 to 100 milligrams for study. However, it’s not clear exactly how much sample material the spacecraft scooped up. JAXA doesn’t have a way to measure how much material Hayabusa-2 collected. However, the agency says that every maneuver went according to plan and that Hayabusa-2 issued the command to shoot its bullet as expected. That makes them all but certain that the spacecraft has some samples in its belly.

In fact, the original Hayabusa was still able to get a sample from its asteroid, Itokawa, even though its bullet projectile failed. During two touchdown attempts, data showed that the bullet firing mechanism didn’t work. But some dust still got kicked up into the sample collector when Hayabusa touched the surface of Itokawa. “If they successfully make contact with the asteroid, something will get up into the sample chamber,” says Lauretta.

Still, gathering samples from an asteroid is an incredibly difficult process. It requires pinpoint precision around an object where there’s very little gravity. That means minute forces, like pressure from solar radiation or any gases coming from the spacecraft, can have a big effect and push the vehicle off course. “When you’re in these microgravity environments around small asteroids, [small forces] kind of push you around substantially,” Lauretta says.

Gathering samples from an asteroid is an incredibly difficult process

To make sure this sample grab went as smoothly as possible, JAXA did multiple dress rehearsals, during which they lowered the spacecraft very close to the spot on Ryugu where the team wanted to grab a sample. Hayabusa-2 even deployed two tiny rovers onto the surface of the asteroid in September, to collect data about its environment. The terrain of Ryugu turned out to be much rockier than JAXA imagined, and so the mission team decided to do some extra tests to make sure everything would still work. The abundance of caution meant delaying the scheduled sampling date from October until today.

Now that Hayabusa-2 has grabbed its sample, it’s possible it will get another one in the months ahead. The spacecraft is carrying essentially a small canon that it can use to impact the surface of Ryugu, exposing rocks deeper within the asteroid. Hayabusa-2 could then lower down and grab another sample from within that crater. However, experts at JAXA have not decided if that will actually happen. Hayabusa-2 is slated to leave Ryugu sometime late this year.

In the meantime, today’s success could be used to ensure that Lauretta’s mission, OSIRIS-REx, is also a success. NASA’s OSIRIS-REx spacecraft launched in September 2016 and arrived at an asteroid Bennu late last year. Sometime next year, OSIRIS-REx will also grab a sample from Bennu, though with a much different kind of instrument than what Hayabusa-2 used. Rather than shoot the asteroid with a projectile, OSIRIS-REx will blow highly pressurized gas on the surface of Bennu, which will hopefully cause rocks to bounce into a collecting plate.

The OSIRIS-REx mission team will prepare extensively for this, but they still don’t know exactly what it will be like to touch the asteroid. “What is the response of that surface?” asks Lauretta. “That’s been the biggest uncertainty that we’ve tried to model.” Lauretta hopes that the Hayabusa-2 team can provide some insight into that.

If all goes well, that means two different asteroid samples will be headed back to Earth in the years ahead. And these pieces could hold clues about the early history of the Solar System and even our own planet. Scientists believe that some of the earliest building blocks of life — such as carbon, hydrogen, and other organic materials — may have come to Earth on ancient asteroids. Finding this material on the rocks circling our Solar System could mean that life is possible in other worlds nearby.

“The likelihood there is life on the subsurface of Mars, or the oceans of Europa or Titan, becomes much higher,” says Lauretta, “if the basic chemistry was ubiquitous in the early Solar System and not unique to the Earth.”

Courtesy/Source: The Verge