This morning, a Japanese space probe deposited two tiny rovers on an asteroid nearly 200 million miles from Earth. The vehicle is Hayabusa2, and the rovers were the first in a series of robots that the vehicle will throw at the asteroid’s surface over the next few months.

Operated by the Japanese Aerospace Exploration Agency (JAXA), Hayabusa2 is tasked with grabbing a sample from an asteroid named Ryugu and returning those materials to Earth. The spacecraft launched in 2014 on top of a H-IIA rocket and arrived at Ryugu in June. It will grab multiple samples from the asteroid in the year ahead before heading back to our planet late nest year.

Ultimately, the goal is to learn more about this asteroid and get a better understanding of what these types of objects are made of. Asteroids like Ryugu are thought to be remnants of the early Solar System, remaining relatively unchanged over the last 4.5 billion years. So they provide a good snapshot of what our cosmic neighborhood was like when the planets were first forming. Studying just a small sample of an asteroid gives scientists a lot of precious information about how our planetary system came to be.

Before Hayabusa2 grabs its samples, the spacecraft will shower Ryugu in robots. The first two that were deployed are Rover-1A and 1B. Hayabusa2 ejected them from a drum called MINERVA-II1 around 12:35AM ET after descending toward Ryugu and coming within 200 feet of the asteroid’s surface. Cylindrical in shape, the rovers are equipped with multiple cameras and temperature sensors to map and image Ryugu. Unlike NASA’s Mars rovers, these mobile bots don’t have wheels. They actually have rotating motors buried within them that enable the rovers to shift their momentum and hop across the surface of the asteroid.

Though their purpose is to gather data, Rover-1A and 1B are also meant to demonstrate that bots can explore a low-gravity environment. Ryugu is a little more than half a mile across, so it doesn’t boast a very strong gravitational pull. That’s why the bots can’t have normal wheels; otherwise, they’d just float away. But this hopping strategy should allow the rovers to explore the surface of Ryugu autonomously without drifting off.

The MINERVA-II1 rovers.
Image: JAXA

MINERVA-II1, the drum that housed the rovers, is actually named after a lander that was carried on the original Hayabusa mission, another JAXA mission that launched in 2003 and became the first vehicle to retrieve samples from an asteroid. However, that lander, named MINERVA, was accidentally released when Hayabusa was too far away from its asteroid, so it got flung out into space and never landed. We still don’t have official confirmation from JAXA yet that these new rovers did indeed touch down on Ryugu. But if they did land successfully, they will have finally fulfilled part of the mission that Hayabusa had originally meant to accomplish.

If Rover-1A and 1B are on Ryugu, they will have more company soon. In October, Hayabusa2 will release another lander, made by the German Aerospace Center, called MASCOT. That vehicle will be released from 328 feet away, and once it’s on the surface, it will also hop across the asteroid in a similar way as the rovers. It’s equipped with four different instruments to measure the geology of Ryugu, as well as study the temperature and magnetic field of the object. Sometime in the coming months, Hayabusa2 will deploy its fourth bot, another rover inside a second drum container called MINERVA-II2.

Of course, the primary goal of Hayabusa2 is to get samples, and the spacecraft will employ some very creative techniques to get up to three different sets of material from Ryugu. The first couple of sample grabs will entail Hayabusa2 getting up close to the asteroid and then shooting it with a gun-like device. That will hopefully stir up enough debris that the probe can gather into its sample collector.

The third sample collection will be much more explosive. Hayabusa2 will attempt to scoop up material from deep within Ryugu, where the rock has been largely unaffected by the space environment. To do that, the spacecraft is going to first set off a small explosive projectile, which will make a crater on the surface. Then, Hayabusa2 will dive into the hole it’s created and gather more rocks. Altogether, the spacecraft should gather a tiny amount of material: just 100 milligrams of dust

All of this will take place over the next year — Hayabusa2 is scheduled to leave Ryugu in late 2019 — so there’s still a long way to go. In the meantime, another US spacecraft will try to capture a lot more material from a different deep-space asteroid named Bennu. That vehicle is NASA’s OSIRIS-REx, which launched in 2016. It will arrive at Bennu later this year and eventually try to grab up to 2 kilograms of dirt from one spot on the asteroid’s surface, before returning to Earth. So if all goes well, two different spacecraft from two different countries may bring back asteroid material for scientists to study.




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