A Japanese spacecraft is set to touch down on a distant asteroid Thursday, before shooting a bullet into the space rock to capture a bit of debris that eventually will be returned to Earth.
Launched in 2014 by the Japan Aerospace Exploration Agency (JAXA), the Hayabusa 2 probe reached asteroid Ryugu in June 2018, after a voyage of 2 billion miles. In the months since then, the refrigerator-sized craft dropped a pair of small rovers on the space rock and has been inching ever closer to its surface. If all goes according to plan, it will fire its thrusters and settle on the asteroid Thursday at about 6 p.m. EST (about 8 a.m. local time in Japan on Feb. 22).
The landing was originally planned for last October, but JAXA postponed it after instruments aboard the rovers found that the asteroid's surface isn't covered with dusty soil (regolith) but is instead strewn with rocks — something scientists had not anticipated.
"The expected topography of a powdery fine regolith was not found on the surface of Ryugu," members of the Hayabusa 2 team said in a Feb. 14 blog post on the JAXA website. "It took time to investigate the safety of the spacecraft during TD," they said, using an abbreviation for "touchdown."
If Hayabusa 2 lands successfully, its next challenge will be to fire the bullet and then deploy a container to collect samples of the material kicked up from the surface by the impact.
JAXA tested the process on Earth, firing a bullet into gravel held within a chamber designed to mimic the vacuum of space. Researchers determined that the resulting rocky debris would be small enough to be collected and brought back to Earth for analysis. But that will take awhile: The samples aren't scheduled to arrive here until late 2020.
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