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Japan (Very Carefully) Drops Plastic Explosives Onto An Asteroid

Apr 5, 2019
Originally published on April 5, 2019 5:45 pm

Early Friday morning, Japan's Hayabusa2 spacecraft detonated an explosive device over a small asteroid. The goal was to create a fresh crater that will later be studied by the spacecraft.

Researchers watched from mission control in Sagamihara, Japan, and clapped politely as Hayabusa2 released an experiment known as the Small Carry-on Impactor. The device consisted of a copper disk packed with HMX high-explosive. Once the mothership had safely moved out of the line of fire, the impactor apparently detonated, firing the disk into the side of the asteroid. A camera released by Hayabusa2 appeared to catch the moment of impact, which sent a stream of ejecta into space.

"It went flawlessly," says Harold C. Connolly Jr., a geologist at Rowan University in New Jersey and a co-investigator on Hayabusa2.

The asteroid is a barren piece of rock known as Ryugu, which measures less than a mile across and orbits between the Earth and Mars. Researchers believe Ryugu may be similar to the early space rocks that merged to make planets, including Earth.

"These particular asteroids are the precursors to what Earth was made from," Connolly says. Ryugu is rich in carbon, and minerals on its surface contain water and so-called prebiotic compounds that could have started life on this planet.

"Ryugu is a time capsule," says Connolly.

The impactor contained high explosives used to fire it into the side of the asteroid. This video shows tests here on earth.
JAXA /Jason Davis /The Planetary Society / YouTube

This is not Hayabusa2's first attack. In February, the spacecraft physically touched down on Ryugu and fired a small pellet into its surface. The dust kicked up by that opening shot was collected and eventually will provide researchers with detailed information about the asteroid's makeup.

But to really understand Ryugu, researchers also want to know what's down there, and that's why they created Friday's crater. In a few weeks, after the dust has settled, the little spacecraft will survey the blast site to see what lies beneath. It may even land a second time to collect subsurface samples.

The spacecraft is scheduled to leave Ryugu later this year, carrying its samples back to scientists here on Earth. On the return, it will eject a pod containing dust from Ryugu that is expected to land in Australia's Outback.

Copyright 2019 NPR. To see more, visit https://www.npr.org.

ARI SHAPIRO, HOST:

Early this morning, Japan's space agency dropped a bomb on an asteroid. NPR's Geoff Brumfiel reports it was done in the name of science.

GEOFF BRUMFIEL, BYLINE: The scene in the control room here on Earth was tense.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON: So very few people are sitting down. They're all standing up.

BRUMFIEL: That's the webcast from Japan's space agency. Scientists and engineers were communicating with the spacecraft known as Hayabusa2. It's currently somewhere between Earth and Mars studying a small asteroid. The team watched as it released a copper disc filled with plastic explosives towards the asteroid, then quickly maneuvered to a safe position. Then the explosives fired, sending the disc flying into the asteroid's surface.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON: And I saw some smiles...

(APPLAUSE)

UNIDENTIFIED PERSON: ...And applause.

HAROLD CONNOLLY JR: It went flawlessly. It was perfect.

BRUMFIEL: Harold Connolly Jr. is a researcher Rowan University here in the U.S. who collaborates on Hayabusa2. He says the explosive projectile was basically designed to dig a hole.

CONNOLLY: The purpose of it is to move material from a deeper depth up to the surface.

BRUMFIEL: So it's not an open act of aggression against another planetary body.

CONNOLLY: It absolutely is not (laughter).

BRUMFIEL: Asteroids like this one have been hanging around the solar system for billions of years.

CONNOLLY: These particular asteroids are the precursors to what Earth was made from.

BRUMFIEL: And it's thought they could teach us a lot about the planet's past, even perhaps the origins of life here. After the dust settles, Hayabusa2 will study the crater created by today's explosion. It may even land and take a sample. Eventually it will return samples to Earth where scientists like Connolly can study them to learn more about how these asteroids and our planet formed. Geoff Brumfiel, NPR News. Transcript provided by NPR, Copyright NPR.