Japan's Hayabusa2 spacecraft detonated an explosive device over a small asteroid. The goal: create a nice, fresh crater that will later be studied by the spacecraft and experts on Earth. (See also Hayabusa 2 To Begin Asteroid Mining .)
(Earthbased test of Hayabusa 2 explosives)
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.
SF writer Edwin Charles Tubb nailed this strategy for determining the composition of asteroids in detail in his 1958 novel The Mechanical Monarch:
Fire streaked in a thin line from the muzzle of a cannon-like tube mounted beneath the viewing instruments and a tiny, rocket-powered projectile, drove towards the mysterious bulk. It hit, exploding into a cloud of incandescent vapour, and Wendis stared thoughtfully at the brilliant lines on the spectroscope screen.
"... the spectro shows traces of iron, some copper, a little tungsten and a lot of beryllium. Looks unnatural somehow, too much like an alloy."
(Read more about the Impactor Determines Composition)