On December 5th, a ball of fire raced across the sky – the sample return capsule of the asteroid mission Hayabusa2 from JAXA (Japan Aerospace Exploration Agency). The capsule landed in Woomera, a remote place in the Australian outback. Earlier this month, the capsule sample containers revealed fine-grain topsoil from asteroid 162173 Ryugu. Since then, a second sample container has been opened containing pieces up to a full centimeter in size.
Soil samples returned from the Hyabusa2 spaceship -c JAXA
Ease the burden
These larger fragments are believed to be pieces of bedrock from Ryugu. They were collected when Hayabusa2 was set up for the second time in July 2019 to collect underground soil. The topsoil was collected when it was first set up in February 2019. Hayabusa2 was able to carry out several touchdown processes on the surface, since Ryugu only experiences microgravity as a relatively small asteroid with a diameter of only 1 km.
The low gravity enables Hayabusa2 to “float” directly above the surface of the asteroid and collect horn with a probe horn. When it was first touched down, the probe fired a small 5 g tantalum projectile into the surface at 300 m / s. In weightlessness, the ejected material could move upwards along the horn of the probe that was thrown into the sample collector. A second planned topsoil collection was scrubbed. A suitable landing site was difficult to find due to the uneven, rocky terrain of Ryugu.
Rotation of Ryugu as recorded by the Huabysa2 probe
CC BY 4.0 JAXA
The underground soil collection in July 2019 was achieved by literally bombarding the surface of Ryugu with the equivalent of an anti-tank anti-tank projectile. Hayabusa2 deployed a free-flying weapon 500 meters from Ryugu's surface while moving to a safe location to avoid being hit by debris. Hayabusa2 also deployed a detachable camera that observed the impact while Hayabusa2 was out of danger. The weapon then detonated an explosive and hurled a 2.5 kg copper cartridge to the surface.
Impact site on Ryugu created by the free-floating Hayabusa2 cannon – JAXA
The resulting impact created a 10 m wide crater that exposed underground soil that was later collected by the probe. The large 1 cm pieces in the container could be pieces of rock that were broken by the impact and broken into smaller pieces upon entering the collection space. The material collected at Ryugu also contains gas samples that are likely to be released from the soils. This is the first time alien gas has ever been collected from space.
"The sample of the alien asteroid material we dreamed of is now in our hands."
Yuichi Tsuda -Hyabusa2 project manager
An explosion from the past
Soil and gas samples have provided more material than the Hayabusa2 team expected, which is great for research. The team will analyze the ground to learn more about the asteroid itself and gain insight into the early history of our solar system. Asteroids like Ryugu are floating time capsules that orbit our sun and record the past of the solar system. When Ryugu was blasted, soils were exposed that are protected from solar radiation and the surroundings of the solar system – essentially a preserved state from the formation of the asteroid billions of years ago. Ryugu was chosen as a target because it was a "C-Type" or carbonaceous asteroid – ancient stone from the early solar system.
These samples will be analyzed for organic matter to understand how organic matter spread in the young solar system and whether it is related to life on Earth. So while we are learning about the history of the solar system, Ryugu can also reveal secrets of our own past.
We also learned more about Ryugu, the asteroid itself. In addition to taking soil samples, Hayabusa2 landed 4 different rovers on the surface. Instead of rolling around on wheels, these “bounced” with rotating masses in order to rotate from the surface under low gravity.
Ryugu's night surface was imaged by the Hyabusa2 MASCOT Rover with red-green and blue LEDs for lighting. MASCOT / JAXA
The rovers were able to capture stunning images and videos of the surface of the asteroids. Ryugu was determined to be a "rubble" object in the solar system. Ryugu is not a solid mass, but a 50% empty space – a collection of stones loosely held together by gravity. This could indicate that Ryugu was shattered by a cosmic impact at some point in the past and then merged under its own gravity as piles of rocky fragments.
Video captured from the surface of Ryugu with Hyabusa2 rovers showing the “day” of the asteroids with the setting sun – JAXA
After retrieving the samples, Hayabusa2 completed a 13-month journey back to earth. At a distance of 220,000 km, the probe released a capsule containing the gas and soil samples that entered the Earth's atmosphere at 12 km / s on December 5, creating a long-tailed ball of fire. Both the outward journey to Ryugu and the return journey recorded a total of 5.24 BILLION km. The solar system is really, really big. The containers were found by several rescue teams in the Australian outback.
Video recorded from Hayabusa2's return capsule
Stripes through the earth's atmosphere – JAXA
Return sample Replica of the Hayabusa return sample capsule (SRC) used for re-entry. The capsule of Hayabusa2 is the same size, has a diameter of 40 cm and uses a parachute to put it on. CC BY-SA 3.0 Mj-Vogel
Back in the distance
This is not the end of Hayabusa2's mission. After completing its main mission, the probe is now on its way to rendezvous with another asteroid, 1998KY26, planned for July 2031. At just 30 m in diameter, 1998KY26 is much smaller than Ryugu and is considered a rapidly rotating micro-asteroid that spans every 10.7 Minutes makes one revolution. The Hayabusa2 rendezvous marks the first visit to one of these rapidly rotating objects, as well as the smallest object in the solar system to be visited by a spaceship. JAXA is also not finished with the sampling of rock worlds. A mission is planned for the mid-2020s to try the Martian moon Phobos.
Universe Today Fraser Cain speaks about JAXA's mission to test Phobos
This era of robotic exploration of the solar system is amazing. Think of everything we just achieved with a 600 kg spacecraft. It fits four rovers, a deployable space cannon, a detachable camera and a variety of sensor equipment in one probe. That and it can make multiple trips to and from Earth while exploring space. We are preparing for a more human exploration of the solar system, but in the meantime, robots are doing the heavy lifting (or the weightless lifting). I'm counting in just a month and a half until Perseverance lands on Mars!
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More to discover::
Even outside the sample capsule of Hayabusa 2 there are asteroid debris – Universe Today
Japan's Hayabusa 2 probe drops pieces of an asteroid and sets off for its next destination – today's universe
Hayabusa2 fires an anti-tank warhead at asteroid Ryugu – Universe Today
Call to Japan! Your Hayabusa2 spaceship collected its first samples from the asteroid Ryugu universe today
Asteroid Ryugu is a "fragile heap of rubble" – universe today
Japanese rovers are now on the surface of an asteroid, sending amazing images back – Universe today
JAXA Hayabusa2 project
Japanese spaceship gifts: asteroid chips like charcoal (phys.org)
Japan's space agency finds plentiful soil, gas from asteroids (phys.org)
MMX – Martian Moon Exploration (jaxa.jp)
Hayabusa2's next next mission: small, fast spinning asteroid | The Japan Times