The Japanese space agency has successfully rendezvoused with a diamond-shaped asteroid millions of miles from Earth.
After travelling for three and a half years, the Hayabusa2 spacecraft made its final approach to the space rock on June 27 and is ready to start its exploration and survey of the asteroid. During its year-and-a-half mission, Hayabusa2 aims to land on the surface of the asteroid three times to collect samples that it can return to Earth in 2020.
Scientists originally thought that 162173 Ryugu, which was discovered in 1999, was a spherical asteroid, but as Hayabusa2 has drawn nearer, the space rock has resolved into a diamond shape littered with boulders.
“From a distance, Ryugu initially appeared round, then gradually turned into a square before becoming a beautiful shape similar to fluorite, known as the ‘firefly stone’ in Japanese,” project manager Yuichi Tsuda said.
“Now, craters are visible, rocks are visible and the geographical features are seen to vary from place to place. This form of Ryugu is scientifically surprising and also poses a few engineering challenges .”
The next stage for the mission is to figure out just where to land its shoebox-sized rover MASCOT by mapping the asteroid’s surface using its cameras and infrared spectrometer. As well as topography, there are a number of other factors to consider.
“First of all, the rotation axis of the asteroid is perpendicular to the orbit. This fact increases the degrees of freedom for landing and the rover decent operations. On the other hand, there is a peak in the vicinity of the equator and a number of large craters, which makes the selection of the landing points both interesting and difficult,” explained Tsuda.
For the next 18 months, this second edition of Hayabusa, Japanese for peregrine falcon, will be maneuvering around the asteroid, while a suite of instruments map it; measure its mass, density, and gravity; determine its mineral and elemental composition; and scout out landing sites.
The first of a series of touchdowns is scheduled for October. In addition to gathering surface soil samples, Hayabusa2 will release a German-French rover called MASCOT that will hop across the surface, using its four instruments to analyze soil samples.
Next spring, Hayabusa2 will blast a crater into Ryugu using a 2-kilogram projectile with a hardened copper nose traveling at 2000 meters per second. (To avoid damage from scattering debris, the spacecraft will hide on the opposite side of the asteroid after releasing the projectile and use a camera to document the collision.)
Images of the impact are expected to shed light on how craters are formed on heavenly bodies. Hayabusa2 will then return to the site of the blast to collect rock samples that have not been subjected to eons of space weathering, hopefully yielding insights into the material as it was during the formation of the solar system. The craft is expected to return its samples to Earth at the end of 2020, reports Science.
Preliminary observations “are really thrilling,” says Seiichiro Watanabe, a project scientist at Nagoya University in Japan.
The diamond-shape asteroid is about 900 meters across and rotates around its own axis every 7.5 hours or so, more slowly than other similarly sized asteroids for reasons that are not yet clear, Watanabe says.
The surface is strewn with boulders larger than would be expected to have accumulated on an asteroid of its size, something that has triggered a debate among planetary scientists.
One line of thinking is that Ryugu was originally part of a larger asteroid that broke up. But others contend the boulders could have landed over time or might have been hard masses incorporated into the asteroid at its formation and later exposed as softer material eroded away. “It’s a strange phenomenon,” Watanabe says.
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June 27th, 2018