Artist's impression of Hayabusa2 above asteroid Ryugu (© Akihiro Ikeshita)
The preliminary analysis of asteroid Ryugu sand samples was completed in March. The samples were brought back by Japan's Hayabusa2 probe after a long six-year journey. It produced significant results that may help unravel the mysteries surrounding the origin of life on Earth and the formation of the solar system.
Moreover, the techniques used for this mission, such as efficient flight to distant celestial bodies for sample retrieval, will be passed down to future generations.
The Hayabusa2 project was led by Professor Yuichi Tsuda of the Japan Aerospace Exploration Agency (JAXA). At a press conference following the completion of the analysis, he reflected on his team's accomplishment: "Our success exceeded our plans in all aspects: science, technology, and exploration."
Hayabusa2 was developed with the goal of bringing back samples from the asteroid Ryugu. It is classified as a C-type asteroid and is believed to contain a high amount of organic matter in its surface rocks. The spacecraft was launched from the Tanegashima Space Center in Kagoshima Prefecture in December 2014.
An ion engine provided propulsion for the approximately 3.2 billion km (1.99 billion miles) journey to Ryugu. It achieves efficient propulsion by utilizing the state of plasma formed by activating ions and other particles.
A Flawless Return Trip
The first Hayabusa, which was launched in 2003, experienced various problems. However, the improved Hayabusa2 operated flawlessly on its return trip, demonstrating its utility.
Hayabusa2 landed on Ryugu in February 2019 and collected surface samples. In July 2019, the spacecraft achieved another successful landing and created a crater on the asteroid's surface by firing a projectile to collect underground samples. Significantly, it was the world's first attempt of its kind. Hayabusa2 departed from Ryugu in November 2019.
The sample capsule separated from Hayabusa2 on December 5, 2020, at an altitude of about 220,000 km (136,700 miles) above Earth. The capsule landed in the southern Australian desert on December 6. During atmospheric entry, ultra-high temperatures exceeding 10,000°C (18032°F) turned the capsule into a fireball, blackening and scorching the surface.
Then, the capsule arrived at JAXA on December 8th after being transported to Japan. The interior was undamaged and appeared brand new. It contained 5.4 g (0.19 oz) of samples, including a roughly 1 cm (0.39 in) stone. This was 54 times the target amount.
The Hayabusa2 mission demonstrated that Japan has successfully established the technology to bring back asteroid samples. The spacecraft is currently en route to another asteroid, 1998KY26, where it is expected to arrive in July 2031.
The Panspermia Theory
After the samples arrived, JAXA began preliminary analysis in collaboration with domestic and international research institutions. They revealed various findings.
Among them were carbonated water containing organic materials and salts, a diverse range of organic compounds required for life, and 23 different amino acids. For the first time in history, liquid water was discovered in a sample collected outside Earth.
Additionally, they also found a substance called uracil. It is one of the bases of the single-stranded nucleic acid RNA, which transmits genetic information in living organisms. In other words, it is a component of the blueprint of life.
The discovery of these substances lends credence to the panspermia hypothesis. It holds that the elements responsible for the origin of life on Earth came from space in the form of meteorites that originated from asteroids.
Furthermore, the analysis revealed the nature of the asteroid Ryugu. Based on the orderly arrangement of metal particles in the samples, the researchers suggest that Ryugu's origin is a highly hydrated asteroid with ice as its main component.
Chemical analysis also revealed that Ryugu belongs in the rare Ivuna meteorite category. This discovery led to the conclusion that Ryugu was formed in the solar system's outermost region, near Uranus and Neptune, and moved to its current orbit near Earth about 50 million years ago.
Furthermore, the sample contained substances that were most likely formed near the Sun during the early stages of the solar system's formation. These discoveries are expected to improve our understanding of the solar system's formation, which occurred approximately 4.6 billion years ago.
Establishing Technology for Future Explorations
Crucially, these accomplishments will be applied to future space exploration worldwide. It is expected that comparing the Ryugu samples with the samples of the asteroid Bennu will yield more information about asteroids. The Bennu samples will be brought back by the spacecraft OSIRIS-REx of the United States in September 2023.
Furthermore, the know-how of sample collection and analysis of Hayabusa2 will be applied to the US Mars rover Perseverance, which is scheduled to return with samples in around 2033.
The ultra-small Japanese probe EQUULEUS, launched in 2022, is attempting a two-year journey to the Moon using minimal fuel by utilizing the gravity of other celestial bodies. This technique also applies the swing-by technology that was successfully developed and used by Hayabusa2.
JAXA's MMX project, which aims to launch in FY 2024 to bring back samples from the Martian moons, is also expected to fully utilize the established technology of Hayabusa2.
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(Read the article in Japanese.)
Author: Juichiro Ito
