The Japanese Hayabusa-2 spacecraft is about to detonate an explosive charge on the asteroid it is exploring.
The operation is designed to generate an artificial crater in the asteroid Ryugu, which the probe has been studying since June 2018.
Hayabusa-2 will later descend into the crater to collect pristine samples of the asteroid that have not been exposed to the harsh environment of space.
The device is known as a Small Carry-On Impactor (SCI).
It’s a 14kg conical container made of copper and packed with plastic explosive.
The SCI is due to separate from Hayabusa-2 at 01:56 GMT on Friday at an altitude of 500m above the surface of Ryugu. At 02:36 GMT, when the device has reached an altitude of 3.5m, it will explode, punching a hole in the surface of the asteroid.
In the meantime, Hayabusa-2 should have manoeuvre itself to hide away on the other side of the asteroid, protecting the spacecraft from any flying debris.
On the way, it will deploy a small camera, called DCAM3. The camera will observe the explosion from a distance of about 1km and transmit images back to its “mothership”.
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 millions or billions of years of bombardment with cosmic radiation is thought to alter the surfaces of these planetary building blocks. So, scientists want to get at a sample that hasn’t been changed by this process.
Speaking at last month’s Lunar and Planetary Science Conference, project scientist Sei-ichiro Watanabe said the experiment would also “provide us with information of the strength of the surface layer of Ryugu”.
This will help shed light on how the asteroid came to be, since it is thought to have been formed by loose debris that was blasted off a bigger asteroid and which then came back together to form a secondary object.
At a later date, scientists may command Hayabusa-2 to descend into the crater and collect a pristine sample of rock. But they will only do so if there is no risk of the spacecraft colliding with a boulder or outcrop.
Follow Paul on Twitter.