The Japanese spacecraft Hayabusa 2 has touched down on Ryugu, the asteroid it's been orbiting since last summer, and collected a sample from its surface.

Practice makes perfect.

Last week, Hayabusa 2 dove to grab a sample from the surface of the asteroid 162173 Ryugu, swooping down like its namesake peregrine falcon. It all went perfectly according to plan: the moment the sample horn made contact a tantalum bullet fired at the surface, knocking away asteroid material that flew up into the horn. Then the spacecraft flew up and away. Hayabusa 2 has now sealed the sample collection compartment, saving the sample for return to Earth in December 2020.

Descent to Ryugu
Hayabusa 2 took this photo with its optical navigation camera from 180 meters before it entered its final descent to grab a sample from asteroid Ryugu.
JAXA / Tokyo Univ. / Kochi Univ. / Rikkyo Univ. / Nagoya Univ. / Chiba Institute of Technology / Meiji Univ. / Aizu Univ. / AIST

It all seems so easy, but that ease didn’t happen without a lot of work and worry. Thirteen years ago, Hayabusa 2’s predecessor, Hayabusa, suffered some kind of damage during its two sampling attempts, and the bullet-firing mechanism didn’t work. It took extraordinary creativity and persistence for Hayabusa’s engineers to bring the spacecraft back to Earth, and the sample capsule it returned contained only a few micrograms of dust. The memory of those struggles weighed heavily on those who worked on Hayabusa 2, one of whom remarked that the successful sample grab was “revenge” for Hayabusa’s travails.

Sample Grab

Finding the right spot to sample Ryugu was more challenging than anticipated. Itokawa had possessed large “ponds,” relatively smooth deposits of dust and small gravel. Hayabusa sampled one of these. But when Hayabusa 2 arrived at Ryugu on June 27, 2018, no such ponds were visible — the asteroid was uniformly rocky.

The team had to develop new sampling site selection criteria, because no site on Ryugu matched the criteria they’d developed before launch. The scientists defined two extremely narrow landing sites where they’d have to navigate the spacecraft between potentially damaging rocks. The team tried out descending toward those sites twice. Back on Earth, they tested whether the bullet-firing mechanism would liberate enough material from a rocky surface; it appeared to, so they proceeded, and it all worked perfectly — probably.

Hayabusa 2 took this picture of Ryugu on February 22nd as the spacecraft began ascending immediately after its brief touchdown. Hayabusa 2's shadow can be seen, along with a dark splotch where the spacecraft's thrusters blew away lighter materials on Ryugu's surface.
JAXA / Tokyo Univ. / Kochi Univ. / Rikkyo Univ. / Nagoya Univ. / Chiba Institute of Technology / Meiji Univ. / Aizu Univ. / AIST

We won’t know for absolute sure just how successful the sampling operation was until Hayabusa 2 returns to Earth. The spacecraft has no way of measuring just how much material made it into the chamber. However, all the spacecraft telemetry, from the velocity profile of the descent and ascent to the temperature changes inside the sample horn, are consistent with successful sampling.

What’s Next?

Hayabusa 2 could actually collect two more samples, placing them into two more collection compartments in the sample return capsule. Now, the mission has to decide whether obtaining the additional sample would be worth the additional risk.

Hayabusa 2 also has a (literally) flashy experiment yet to perform. It has a deployable Small Carry-on Impactor (SCI), a mostly copper spacecraft containing explosives that can create an artificial crater on Ryugu’s surface. Hayabusa 2 will shelter from the explosion behind the asteroid’s bulk, but it would be a shame to set off a firework and not get to see it explode. So Hayabusa 2 also has a deployable camera, DCAM3, which it will release shortly after SCI deploys to (hopefully) obtain views of the crater’s formation. If the experiment is successful, the team would follow by sampling material from the crater. Being able to directly compare material from the asteroid’s weathered surface to its relatively pristine interior would be a boon to scientists, who must often determine bulk composition from remote observations of asteroids’ surfaces.

Hayabusa 2 must wait for planetary alignment to start its journey back to Earth, so it will remain in proximity to Ryugu until November or December. Its return will take about a year. After dropping the sample in the Australian desert on December 7, 2020, the spacecraft could potentially go on to an extended mission, a flyby past another asteroid. Hopefully, the sample capsule will contain lots of asteroid material, which Japan will share with researchers and labs around the world.


Image of Robert-Casey


February 25, 2019 at 5:51 pm

Maybe have a small cell phone camera's lens mounted in a hole of the collection container. And take a picture to see how dirty the lens gets after an attempted sample collection?

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March 1, 2019 at 7:44 pm

Whenever someone complains about science and scientists on regard to anything, but usually related to climate change, show them this article as to what science and scientists can accomplish. What Japan has done, and is doing, is amazing.

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March 2, 2019 at 5:09 pm

Jammer! your assertion do not belong to a Scientist mind.
To put together two different casted sets of different thinking to try to improve the wrong one, it is more of a politician statement.
Climate Change and THIS Amazing Japanese scientist achievement, it is like to compare italian food made in USA and made in ITALY. A bunch of marketing in between.
Pollution surely exists but climate change it is a mystified attempt to drive easy consent when minds are too "weak" to understand ample variables to be held together.
Please just pick the last news proof, which came out few days ago, of the imprisonment of the biggest scientist supporter of Climate Change! ... This is not all surely but way more related than your weak equation.
Science should stay away from Politics preachily like Religion does, as much as they can coexists:
Only love
los angeles

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March 5, 2019 at 5:08 pm

Here is a video (on Twitter) of Hayabusa2 touching down, firing it's tantalum bullet and the resulting debris cloud:

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