Hayabusa-2: Japanese probe likely to have ‘bombed’ an asteroid

Hayabusa2 Image copyright Akihiro Ikeshita
Image caption Artwork: Scientists want to retrieve a pristine sample of material from the crater

The Japanese Hayabusa-2 spacecraft is thought to have detonated an explosive charge on the asteroid it is exploring.

Its mission is to create an artificial crater on the asteroid Ryugu.

If this is successful, it will later return to gather samples of the asteroid, which could help scientists understand how Earth was formed in the early Solar System.

According to Kyodo News, the experiment’s success will only be confirmed in late April.

The explosive device, called the Small Carry-on Impactor (SCI), was deployed by the Hayabusa-2 on Friday. The SCI is a 14kg conical container attached to the Hayabusa-2 and packed with plastic explosive.

It was intended to punch a 10m-wide hole in the asteroid upon impact.

The SCI on Friday successfully separated from the Hayabusa-2 at an altitude of 500m above the surface of Ryugu.

In the meantime, the Hayabusa-2 manoeuvred itself to hide away on the other side of the asteroid, shielding the spacecraft from any flying debris.

If the detonation is successful, images of the moment it happened should have been captured by a small camera called DCAM3 that was deployed by the Japanese Aerospace Exploration Agency (Jaxa) probe.

The camera is meant to observe the explosion from a distance of about 1km and capture images of the projectile explosion back to its “mothership”.

However, it is unclear how long it would take for these images to be transmitted back to Earth.

If all goes to plan, Hayabusa-2 will in a few weeks return to the crater to collect pristine samples of the asteroid that have not been exposed to the harsh environment of space.

These samples are expected to reveal vital data to help explain how planets were formed in the early period of the solar system.

Yuichi Tsuda, the mission’s project manager, had earlier explained: “We expect the impact accuracy [of the SCI] to be something like a 200m radius, it’s very large… we expect to have a hole somewhere in that very big region.

“We will try to find that artificial crater two weeks later, by descending to a lower altitude and making extensive observations.”

A video of the SCI being tested on Earth can be seen below:

Ryugu belongs to a particularly primitive type of space rock known as a C-type asteroid. It’s a relic left over from the early days of our Solar System.

But bombardment with cosmic radiation over the aeons is thought to alter the surfaces of these planetary building blocks. So, scientists want to get at a fresh sample that hasn’t been changed by this process.

Speaking at last month’s 50th Lunar and Planetary Science Conference (LPSC), project scientist Sei-ichiro Watanabe said the experiment would also “provide us with information of the strength of the surface layer of Ryugu”.

This could help shed light on how the asteroid developed its characteristic “spinning top” shape.

Image copyright JAXA, Uni Tokyo & collaborators
Image caption Ryugu has a characteristic “spinning top” shape

Scientific results suggest Ryugu was formed from loose debris that was blasted off a bigger asteroid and which then came back together to form a secondary object.

At the LPSC meeting, held in The Woodlands in Texas, Yuichi Tsuda told me how the team decided where on Ryugu to generate the artificial crater.

“There are two things: the first priority is to make a hole where we can easily identify a crater… so, easy observation, not too hard, not too bumpy,” he said.

“Second, somewhere that’s as feasible as possible in terms of landing… if those two don’t meet together, we go with the first priority.”

Scientists may command Hayabusa-2 to descend into the crater at a later date to collect a pristine sample of rock. But they will only do so if there is no risk of the spacecraft colliding with a boulder.

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