Scientists studying asteroid treasure box find cleanest rocks in solar system ever studied

When the Japanese aircraft Hayabusa2 threw his chest with asteroid samples towards Earth in December 2020, scientists and engineers who took the samples home erupted in applause. Later an eight-year mission to the 4.6 billion-year-old asteroid Ryugupieces of ancient rock are finally on their way to Earth.

Now, some eighteen months later, the crate is open and its treasure subjected to a full spectrum of scientific analysis. The Japanese space agency, JAXA, has predicted that the valuable materials inside the Hayabusa2 sample capsule will be of great scientific value – and initial chemical analysis shows how exceptional the agency’s samples are.

In a study published in the journal Science on June 9, JAXA scientists gave the first detailed assessment of samples returned from Ryugu since they were returned to Earth.

“We found Ryugu to be the freshest CI chondrite ever,” said Shogo Tachibana, JAXA’s lead scientist at the initial sample analysis.

This means that the materials found by Ryugu are the most primitive that humans could ever analyze on Earth. They provide a portal to the earliest days of the solar system, when the Sun was just a young star and the planets were just beginning to form. Although the study released on Thursday is a major milestone in understanding Ryugu, it is only the first step in understanding the solar system and our place in it.

Here’s why it’s important.

Journey to the Dragon Palace

Japan’s Hayabusa2 mission was launched in 2014 on the way to take samples from the asteroid Ryugu, named after “Dragon Palace” in a famous Japanese folk tale. The asteroid belongs to the most widespread class in our solar system, C-type, and is shaped like a rotating top. Its orbit around the Sun exists behind Mars. Some scientists believe that these types of asteroids delivered raw materials for life to Earth, and that is why JAXA wanted to explore Ryugua and steal some rocks from its surface.

After a four-year voyage, Hayabusa2 encountered a space rock, and then, in 2019, the spacecraft made two short landings on the asteroid, taking samples and storing them in a specialized sample capsule. That sample capsule landed in the Australian wilderness in 2020 and has been carefully managed with its precious cargo ever since.

Two landings on Ryuga took away 5.4 grams of material from the surface and below the surface of the asteroid. The material is in the form of small gravel and stones, up to about 0.4 inches in size. In a study published on June 9, an extremely small amount of sample – about 2% of the total – was taken to examine the chemistry and structure of the asteroid and draw some conclusions about how it formed and transformed during its lifetime. This required powerful electron microscopes and the use of spectrometers, which can provide details about the chemicals present in an object based on how the object reflects light.

Scientists conclude that Ryugu probably formed after a huge space rock in the early solar system was shattered. The material that was ejected eventually formed into an asteroid with a rotating tip known as Ryugu. This impact, according to analysis, probably occurred about 2 million to 4 million years after the formation of the solar system. Based on the way the samples were altered by water, scientists believe they date back about 5 million years after the formation of the solar system.

“Everything happened at a very, very early moment [in regard to] the formation of the solar system, “says Tachibana.

Cool, isn’t it? But … what does all this mean?

Why meteorites are important

To understand the importance of patterns, it is best to look at pieces of rock that have fallen to Earth. Scientists call them “meteorites”.

Meteorites can be classified into different groups based on their composition and chemistry. The rarest type of meteorite scientists have seen is known as “CI krondriti” – since the 1800s, we have seen only five meteorites of this class fall to Earth. One of the most famous is the fall of Orgueil, which occurred in France in 1864.

“[U]Unlike other groups of meteorites, the chemistry of CI chondrites has not evolved or been modified, and they can tell us about the initial composition of the solar system, “said Ashley King, a scientist who heads the Department of Mineral and Planetary Sciences at the Natural History Museum in the UK.

In short, CI chondrites are the most primitive rocks we have ever found. They come from a time when the solar system was just beginning to form. But the rocks that reach the Earth are altered by our atmosphere and our journey to the Earth. When they hit the atmosphere, they heat up and create new minerals and chemicals, and then, when they land, they are changed by moisture and interaction with water.

This was a riddle for meteorites, scientists who specialize in studying meteorites, because – until Ryugu – we didn’t have the opportunity to know what the chemical composition of the asteroid actually was. All that changed with JAXA’s analysis and thrilled some meteorite scientists.

“I’m basically stuck in fear of this study at the moment and it’s hard to translate in normal words how interesting and important it is to have a source of this type of meteorite available for future study,” said Gretchen Benedix, a planetary scientist at Curtin University in Western Australia.

To sum up, scientists now have access to the earliest epoch of our solar system and the implications for future studies are profound. Think of it this way: JAXA scientists have investigated a meteorite that never reached Earth and therefore has never been altered by conditions on our planet. That is a monumental result.

“Ryugu samples are the most chemically primitive alien material currently available for study and will lead to new discoveries in our understanding of the origins and evolution of planetary systems,” King said.

What now?

This first paper is just the beginning for JAXA scientists. In the next few months, much more detail about the Ryugua specimens is expected to be revealed, revealing details about the rock’s magnetism, how it was affected by space weather and its exposure to the solar wind and cosmic rays.

But it’s not just JAXA interested in Ryugu. NASA purchased 10% of the returned samples in December 2021 and will conduct its own analysis of the samples, asking to compare the finding with its mission to return asteroid samples, Osiris-Rex, which visited the asteroid Bennu in 2020. That mission is the samples are expected to return to Earth in September next year.

What are all waiting for scientists to discover? The possibilities are endless. Just this week, reports suggested that JAXA had also discovered amino acids – the “building blocks of life” – in Ryugu. A full scientific report on Ryugu’s amino acids has yet to come, but this discovery contributes to the idea that organic compounds may have been delivered to Earth from space.

As scientists study the grains of rocks from Ryugu and Bennu, our vague understanding of the earliest times in the history of the solar system will gradually come into focus. It could potentially even reveal where we come from.