Tonight, a Japanese spacecraft will try to fire a bullet at a giant rock in space. If it succeeds, it could help advance understanding of how our planet formed in the early solar system.
Last June, Hayabusa2, the Japanese probe, crept up on an asteroid called Ryugu. It surveyed the object’s surface, and in the following months landed multiple robotic probes on its rocky terrain. All that work was done to support the aim of collecting samples from Ryugu’s surface and later bringing them home to Earth. On Thursday (it will be Friday in Japan), the probe will make its first of a series of attempts to touch down on the asteroid’s surface.
When will the spacecraft land on the asteroid and how can I follow it?
The spacecraft, which is now about 200 feet above Ryugu and descending autonomously, will land around 6:25 p.m. Eastern time on Thursday (8:25 a.m. on Friday in Japan). JAXA, the Japanese space agency, will stream coverage of the event with English-language translations on its YouTube channel, or you can watch it in the embedded player below.
What will Hayabusa2 do when it lands?
Hayabusa2 will collect material from the rugged surface of the asteroid with a device called a sampler horn.
To make small enough fragments, the spacecraft will fire a projectile made of the metal tantalum — basically a bullet — at the asteroid’s surface. Earlier this month, the mission’s managers reported their simulation of this procedure on Earth to demonstrate that it would be able to succeed.
The landing and collection won’t take long — about one second, according to the Planetary Society. Then Hayabusa2 will rise from the surface and return to a safe distance near Ryugu.
The spacecraft will be able to cancel its landing should it detect a problem on the boulder-strewn surface that would threaten its success. It is also carrying multiple projectiles so it can make more than one attempt at a touchdown. In March or April, Hayabusa2 is also expected to send an explosive package called a Small Carry-on Impactor to Ryugu’s surface to make an artificial crater. Hayabusa2 might collect another sample of the material exposed in the crater.
Why are they studying this asteroid?
Asteroids are bits and pieces leftover from the disc of gas and dust that formed around the young sun and never quite coalesced into a planet. They contain some almost pristine compounds that help tell what the early solar system was like 4.5 billion years ago.
Ryugu, as dark as coal, is a C-type, or carbonaceous, asteroid, meaning it is full of carbon molecules known as organics including possibly amino acids, the building blocks of proteins. Such molecules are not always associated with biology and can form from chemical reactions in deep space, but asteroids could have seeded Earth with the organic matter that led to life.
About three-quarters of asteroids in the solar system fall into the C-type.
This space rock was discovered in 1999 and not given a name until 2015. Ryugu is named after Ryugu-jo, or dragon’s palace — a magical undersea palace in a Japanese folk tale.
Isn’t NASA doing something like this too?
Yes. The Osiris-Rex spacecraft is currently surveying another carbon-rich asteroid known as Bennu, and it too will collect samples and return them to Earth. Bennu is even smaller than Ryugu, about 500 yards wide. Osiris-rex will not return with its samples until 2023.
NASA and Japanese scientists plan to exchange samples of the two asteroids to compare the similarities and differences.
Has Japan done this before?
As the 2 in Hayabusa2 indicates, this is the second time that JAXA, the Japanese space agency, has sent a spacecraft to an asteroid.
Hayabusa2 is an improved version of Hayabusa, which visited a stony asteroid, Itokawa, in 2005. Despite several technical problems at Itokawa, Hayabusa returned a capsule to Earth in 2010 containing 1,500 particles from the asteroid.