Quirks & Quarks

Japanese space scientists shot an asteroid to learn about its past

The tiny, rocky asteroid Ryugu, in orbit between Earth and Mars, gives up some of its secrets.

The tiny, rocky asteroid Ryugu, in orbit between Earth and Mars, gives up some of its secrets.

Artist's conception of Hayabusa2's arrival at Ryugu (JAXA)
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The unmanned Hayabusa2 spacecraft, launched by Japan's Aerospace Exploration Agency (JAXA), in 2014, made its rendezvous with the one kilometre in diameter near-Earth Asteroid Ryugu almost two years ago.

As part of its mission it fired a two kilogram copper cannonball into the asteroid's surface from very close range. The resulting artificial crater displaced about "10,000 buckets of sand," according to Seiji Sugita.

Sugita is a principal investigator with the Hayabusa2 mission, and professor in the Department of Earth and Planetary Science at the University of Tokyo. 

Ryugu's age and composition 

Making the crater gave researchers the opportunity to learn more about the asteroid's age and composition. The crater was semicircular in shape and measured just over 17 metres across at its widest point. Previous observations revealed that Ryugu was composed of sand and boulders.  The impact revealed that the material wasn't well consolidated, or bound together,

An image taken from Hayabusa2 of the ejecta plume after the impact of a 2kg copper ball on the surface of the asteroid. (Arakawa et al. (2020))

Results from examination of the crater, and other naturally created craters on Ryugu, suggest that Ryugu may only be about 10 million years old.

Hayabusa's return to Earth

The Hayabusa2 spacecraft will return to Earth in December of this year. Scientists like Sugita are especially excited about that because of its special cargo.  Earlier in its mission Hayabusa2 had touched down on the asteroid and scooped a small sample of its surface.

When the spacecraft launched the projectile into the surface, special equipment on board also collected a tiny amount of material  — or ejecta — from the plume created by the impact. Combined, these samples will will provide more definitive information about asteroid Ryugu.

 

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