ST. GEORGE — The final asteroid lander in Japan’s six-year Hayabusa 2 mission to survey Ryugu, a 3,000-foot-wide near-Earth asteroid, made a successful touchdown Thursday.
The $270 billion Hayabusa 2 mission launched in December 2014 and arrived in orbit around Ryugu in late June of last year. Ryugu was chosen because the asteroid is classified as a primitive carbonaceous asteroid, a type that is a desirable target because it represents the primordial matter that formed the bodies in the Solar System. The asteroid is also a target that’s relatively close to Earth.
Additionally, the asteroid’s subsurface material is an important payload for scientists because the samples have been protected from the harsh effects of cosmic rays and charged particles of solar wind blasting through space.
The spacecraft arrived on Ryugu carrying with it four small rovers for what was to be a basic sample-return mission, but the Japan Aerospace Exploration Agency, known as JAXA, decided to send the rovers to explore the asteroid’s surface and gather as much information as possible during the visit, even though there was no guarantee that the sample return would be successful.
The spacecraft covered more than 180 million miles on its three and a half year journey through space. It takes radio signals traveling at the speed of light 20 minutes to go that far, yet Hayabusa 2 touched down on Ryugu with an accuracy of fewer than three feet.
Hayabusa 2 deployed two tiny, hopping, rovers, the second of which, dubbed MINERVA-II2, landed last week to explore the space rock and gather a variety of data, including the gravitational field exerted by the asteroid. Scientists will also be able to study the rover’s long, slow path, about 5 inches per second, down to Ryugu’s surface with the main spacecraft watching from about 5 miles above the surface. The rover’s mission is expected to end on Tuesday.
Video clips of the landing along with photos taken of the asteroid and the Hayabusa-2 lander can be viewed at the top of this report.
Last year, Hayabusa-2 deployed a shoebox-sized lander named MASCOT, an acronym for the Mobile Asteroid Surface Scout, on Oct. 3, 2018, that landed on Ryugu and, after tumbling around for a few seconds, it traveled across the rocky landscape for 17 hours, taking measurements of temperature and magnetism. It was also equipped with MAScam, an LED camera used to take flash photos.
Since the toaster-sized robotic adventurer was battery-operated, once it completed its mission, it powered down for the last time.
MASCOT was deployed from only 134 feet above the asteroid and, with no wheels, it tumbled to a stop before using its internal spring arm to jump to a new location, a method of transportation it would use for the duration as it hopped around the asteroid.
The robot’s short mission provided a wealth of information on the asteroid’s composition, which recent analysis shows that the asteroid’s surface is comprised of two different types of rock distributed evenly. Some were dark, like charcoal, with crumpled, cauliflower-like surfaces, while the other type consisted of brighter rocks with sharp edges and smooth, fractured surfaces.
The images sent back to earth, along with measurements taken along the surface, has characterize Ryugu as a “rubble pile” with very little cohesion.
The composition supports the theory that Ryugu was formed from some type of cataclysmic event. For example, an asteroid made up of bright, smooth stone could have collided with a dark, rough object, which sent debris flying in all directions. Once gravity compacted the rubble together, it could have formed the asteroid.
Other experiments have shown that Ryugu is not very dense. In fact, its average density is slightly more than ice and is riddled with cavities, likely making it a fragile body.
Scientists also found that some of the rocks that make up the asteroid may be similar to carbonaceous chondrite meteorites, which include some of the oldest rocks in the solar system that could be 4.5 billion years old – the same ones that have crashed into Earth before. The asteroid is also made up of rocks that may contain olivine, a very common mineral on Earth that creates a green hue and a mineral that has also been found on the moon and Mars.
One thing researchers didn’t find on Ruyugu was dust, which they said was peculiar since frequent bombardment with other objects should have left the rocks with a layer of dust. One reason may have to do with the asteroid’s gravity, which is only about one-sixtieth of the gravity on earth, which could have caused the dust to either fall into the cavities of the asteroid or just escape into space, Ralf Jaumann said in a German Aerospace Center press release in August.
“Ryugu’s entire surface is littered with boulders, but we have not discovered dust anywhere,” Jaumann said in the release. “It should be present, due to the bombardment of the asteroid by micrometeorites over billions of years and their weathering effect.”
The Japanese spacecraft Hayabusa 2 made a carefully choreographed second touchdown on the asteroid July 10, after deploying a copper bomb to create a man-made crater on the space rock. The images beamed back to Earth show the perspective of two different on-board cameras — the main navigation camera and a publicly funded camera pointed past the sampling mechanism.
Hayabusa 2 will embark on its year-long journey home in December, along with its payload of samples taken from the asteroid’s surface that will be stored in a capsule which is expected to land in the deserts of South Australia in December 2020. The invaluable payload will give scientists an opportunity to analyze the asteroid, along with the photos taken during the mission, in the hopes of unlocking the space rock’s origins.
This is important, Jaumann said, since Ryugu is a near-earth object, and if it ever passed dangerously close to the planet, “and an attempt had to be made to divert it, this would need to be done with great care.”
If impacted with great force, he continued, the entire asteroid, weighing more than half a billion tons, would break up into numerous fragments weighing several tons each, sending them on a collision course with earth.
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