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A Japanese space capsule is about to touch down in the Australian outback, and while it could be carrying as little as a gram of space dirt collected from an asteroid, scientists are hoping it could reveal a lot about the early solar system.

A space capsule carrying dust and rocks from an asteroid is due to land in the South Australian desert early on Sunday morning.
Key points:

  • The Hayabusa2 spacecraft launched in 2014 and took four years to reach its destination
  • Its capsule is only hours away from landing back on earth
  • Scientists hope to learn a lot about the early solar system

The Japanese Hayabusa2 capsule, which is returning from its mission to the asteroid Ryugu, is due to touch down on the Woomera Prohibited Area about 500 kilometres north-west of Adelaide at about 4:00am (local time).
It will put on a spectacular show in the early morning twilight as it streaks towards Earth.
Then the hunt will be on to find its landing spot.
“This is the grand finale of a 10-year effort, if you include development time and the six-year journey of the spacecraft itself,” said Masaki Fujimoto of the Japan Aerospace Exploration Agency (JAXA).
Professor Masaki Fujimoto in Woomera.(ABC News: Sarah Mullins)
Professor Fujimoto said the mission would help scientists answer some of the fundamental questions about how our solar system formed and where elements such as water came from.
“By studying the sample from Ryugu we’ll be able to understand the process that made our planet habitable,” he said.
“The reason we care about these primordial asteroids is that they are linked to the process that made our planet happen.”
The Hayabusa2 mission is returning space rocks to Earth this weekend.(Supplied: JAXA)
Hayabusa2 will be the second asteroid sample mission to return to Woomera, a 122,000-square kilometre defence area that encompasses the traditional lands of six Aboriginal groups.
In 2010, Hayabusa1 returned with specks of dust blown off the surface of an asteroid called Itokawa.
There are many similarities between the two missions, and some key differences.
The mission at a glance
Launched in 2014, it took four years for Hayabusa2 to reach the lumpy diamond-shaped space rock between Earth and Mars.
After launching in 2014, it took about four years for the craft to reach Ryugu.(Supplied: JAXA)
When it got there, scientists realised Ryugu was covered with a lot more big boulders than they anticipated, but they eventually set down two “hopping” roversand blasted a crater to collect rock fragments.
While Hayabusa1 collected dust off the surface, this is the first mission to collect rocks from underneath the surface.
“When we got to Ryugu we were so shocked to see the rocky surface everywhere so it was really tough to find any landing spot at all but we did the touchdown twice,” Professor Fujimoto said.
Cameras on the spacecraft indicate it picked up about 1 gram of space dirt.
“One gram may sound small for some of you, but for experts one gram is enough to address the science questions we’re hoping to [answer],” he said.
In November last year, the spacecraft began its journey back to Earth.
After travelling more than 5.2 billion kilometres over six years, it is lined up ready to send the capsule towards Earth.
Unlike last time, the Hayabusa2 spacecraft itself will not return to Earth.
Instead, after it separates from the capsule a day ahead of the landing, it will fly away on a new mission to rendezvous with three other asteroids between 2026 and 2031.
An artist’s impression of the space craft touching down on Ryugu.(Supplied: JAXA)
So what’s the plan for landing?
As the capsule descends towards Earth at supersonic speeds, its trajectory will be tracked by teams of scientists spread across hundreds of kilometres on the ground and in the air.
As the sole international observer, Australian scientist Trevor Ireland will be on board the helicopter tasked with spotting the capsule somewhere in an area tens of kilometres wide.
“We should know pretty much where it is as it comes down,” said Professor Ireland of the Australian National University, who was also on the science team for the Hayabusa1 mission.
The planned re-entry for the Hayabusa2 space capsule.(Supplied: JAXA)
As the capsule slows down in the Earth’s atmosphere, the heatshield around it will light up as a fireball for about 40 to 50 seconds above Coober Pedy, 400 kilometres north of Woomera.
“Last time it was very spectacular because the spacecraft came in with it,” Professor Ireland said.
“This time we don’t want it to be quite so spectacular, we just want to see that nice red glow of the space capsule coming in.”
Once the capsule slows down enough, it will deploy a drag parachute and then a second main parachute.
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Scientists, including four teams from the Desert Fireball Network at Curtin University, will track the trajectory of the capsule as it streaks across the sky.
“The Desert Fireball Network team will be putting out cameras all the way along the Stuart Highway to take pictures of this bright shooting star,” said team leader Ellie Sansom, who is currently in Coober Pedy.
The Desert Fireball Network has also partnered with a group of Japanese researchers who cannot be in Australia due to the COVID-19 pandemic, and is putting out instruments from them that listen to the sonic boom and detect any ground shaking.
“It’s going to be just so exciting to see this thing coming in you can even hear the sonic boom with your own ears,” Dr Sansom said.
Back in Woomera, more than 70 Japanese scientists will track the descent using radar, Professor Ireland said.
“The radar guys will get a much longer view of it as it comes in because once the parachute opens up they’ll have a bigger object to look at,” he said.
A radio beacon on the capsule will help the Japanese scientists refine the position.
“The radio signals were within a few hundred metres last time,” Professor Ireland said.
Meanwhile, NASA scientists flying on two aeroplanes will observe how material blows off the heat shield of the capsule as it descends.
Mission control at the Woomera Prohibited Area, where Royal Australian Air Force personnel are assisting the Japanese Aerospace Exploration Agency.(ABC News: Sarah Mullins)
Could the weather affect the landing?
Clouds not really. Wind definitely.
Meteors fall into Earth’s atmosphere all the time regardless of clouds, but strong winds could affect where the capsule lands.
“When the capsule is under parachute it can travel a reasonable distance,” Professor Ireland said.
“That last 10 kilometres is the big issue as it’s coming down, once it gets into our weather systems.”
Professor Ireland holds a vial of moon dust collected by Neil Armstrong.(Supplied: Australian National University)
If the weather isn’t kind, it will make the retrieval a little trickier too.
“If it’s not a very nice day, they’ll try to get it contained very quickly so it doesn’t get covered in dust or rain.”
What happens when it lands?
Once the capsule lands, a team including Professor Ireland will head out to search for it.
“I’d be very surprised if it’s a long search,” he said.
“It’s got an obvious parachute on the ground, so it’s quite distinctive when you’re flying around.”
The capsule carries samples that, while small, will be of huge interest to scientists.(Supplied: JAXA)
Once the capsule is deemed to be safe, the team can get to work to make sure there are no cracks or contamination.
“The last one [from Hayabusa1] was absolutely pristine, there was not a mark on it,” he said.
“It’s been inside these heat shields as it’s coming down, and space is not a dirty environment so we don’t think there will be too much contamination on it.”
The Woomera Range Complex is used for launches as well as landings.(Supplied: Australian Department of Defence)
The team will then take the sample back to the base, where they check for gas coming off the capsule an early indication they’ve got a sample inside.
It will then be packed up and sent back to Japan for weighing and analysis.
“We should have a pretty good idea within a couple of weeks that there’s a sample there,” Professor Ireland said.
What are scientists hoping to learn?
Asteroids can tell us about how our solar system formed.
“All of these little bits of information are important when figuring out what happened 4.5 billion years ago,” Professor Ireland said.
While Itokawa is an S-type or stony asteroid thought to come from the inner solar system, Ryugu is a C-type asteroid, which are believed to contain organic material and water from the outer solar system.
Although C-type asteroids are the most common type (about 75 per cent of asteroids are C-type), meteorites from them rarely make it to Earth.
“If we can relate both of these two types of asteroids to the meteorites that come on to Earth, then we have a far better fix on what’s actually happening with our meteorite collections.”
The surface of the asteroid Ryugu, from an altitude of about 64 metres.(Supplied: JAXA)
That said, there are many more meteorites and asteroids out there.
NASA’s OSIRIS-Rex mission, which is currently exploring another C-type asteroid called Bennu, will return to Earth, landing in Utah in 2023.
Professor Ireland will also be involved in the analysis of dust from Bennu.
“Sample returns are really expensive, but they are really important,” he said.
“Meteorites are nice, they give us those postage stamps of the early solar system, but there’s nothing like actually getting a sample.”
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