The Japan Aerospace Exploration Agency (JAXA) has confirmed that, earlier this month, its Hayabusa2 deep space probe became the first spacecraft to successfully bomb an asteroid. By comparing before and after images of the impact site taken of the asteroid Ryugu by the spacecraft's Optical Navigation Camera - Telescopic (ONC-T), the space agency determined that the SCI (Small Carry-on Impactor) device detonated on impact, creating an artificial crater.
On April 5, 2019, Hayabusa2 deployed the SCI, which was an impactor equipped with a plastic explosive charge formed into a cone and lined with 2-kg (4.4-lb) of copper. The principle behind it is the same as that of an armor-piercing rocket grenade. When the SCI was fired at the surface, the charge detonated and the copper turned into a molten slug that blasted open a crater in the asteroid, exposing buried material that has been protected from sunlight and damaging radiation for billions of years.
The problem was that it wasn't safe for Hayabusa2 to remain in the vicinity because of the danger of debris blasting back from Ryugu. So, in the interests of safety, the probe retreated below the asteroid's horizon and out of line of sight. However, the deployable camera, DCAM3, did record a plume of gravel near the impact zone.
Because DCAM3 didn't have the resolution needed to look for the actual crater formed by the SCI, JAXA ordered Hayabusa2 to execute a series of orbital maneuvers and descend over a two-day period to an altitude of about 1.7 km (1.1 mi). By comparing images from the flyby with ones taken on March 22, mission control was able to confirm the existence of the new crater.
The purpose of the asteroid bombing is to uncover a deep area from which pristine samples of Ryugu can be collected by Hayabusa2 and returned to Earth. This will not only serve pure science, but will allow scientists to gain new information about the structure and composition of asteroids, which may one day prove helpful in the event one on a collision course with Earth needs to be deflected or destroyed.
"The exact size and shape of the artificial crater will be examined in detail in the future, but we can see that terrain of an area about 20 m (66 ft) wide has changed," said JAXA via Twitter. "We did not expect such a big alternation so a lively debate has been initiated in the project."
Source: JAXA
