A Japanese space mission that has been studying an asteroid not far from Earth on Thursday night (Friday in Japan) attempted to fire a copper projectile at its surface. While the detonation of the explosive was not yet confirmed, the spacecraft’s other operations were successful.
The operation’s goal was to create a crater on the space rock. If successful, the spacecraft could touch down on the asteroid in the weeks to come, and scoop up samples that could help scientists understand how our planet formed in the early solar system.
Since last year, the Japanese probe, Hayabusa2, has been studying the asteroid, Ryugu, with the aim of returning its collected samples to Earth in 2020.
Hayabusa2 began by surveying the object’s surface, and subsequently landed multiple robotic probes on the asteroid’s rocky terrain. In February, Hayabusa2 fired a much smaller projectile into the asteroid’s surface during a brief touchdown, collecting samples from the cloud of debris that the operation kicked up.
Why make a crater on the surface?
Hayabusa2 already has landed briefly on Ryugu’s surface and collected samples. But the surface materials scattered by the bullet-like projectile fired in February have been exposed to the solar system’s weather. Studying them offers scientists a potential picture of Ryugu’s surface. But that debris won’t reveal much about the asteroid’s geological history, just as the topsoil in your yard won’t tell you much about what your neighborhood was like during the last ice age.
Making a crater will also offer clues to how asteroids similar to Ryugu respond to being struck by objects.
How did Hayabusa2 try to make the crater?
Hayabusa2 carried a device called the Small Carry-on Impactor. Unlike the small tantalum projectile that was fired at the asteroid in February as the spacecraft touched down on the surface, the impactor device detached from the spacecraft. That allowed the probe to race to the other side of Ryugu and avoid damage from the anticipated explosion or the resulting debris.
The impactor was made of copper. According to the Planetary Society, a funnel containing plastic explosive was to hurl the copper projectile into the asteroid’s surface, making a crater that could be as large as about 30 feet wide. The spacecraft also launched a small camera that attempted to record the explosion.
Before scientists elect to have the spacecraft collect samples from the crater, which would happen some weeks from now, they will make sure the landing conditions are safe. If not, they will collect measurements of the crater using instruments aboard Hayabusa2.
Why are scientists 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. Early research results announced last month also revealed that Bennu is more rugged than expected, and that it is shooting rocks from its surface into space.
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.