The samples contain the most pristine material from the early days of our solar system that scientists have ever seen.

The monsters of asteroid Ryugu, brought by the spacecraft Hayabusa2, surpass all expectations. The spacecraft delivered about five grams of material to Earth at the end of 2020, after which scientists were eager to analyze the Ryugu samples. And the preliminary results are astonishing. “These monsters are the leftover bits of the solar system, the crumbs on the counter that you spill when you make a cake,” said study researcher Brad Tucker of the Australian National University† “It gives us insight into what the solar system looked like billions of years ago.”

CI-chondrites

The samples are classified as carbonaceous chondrites of type CI. And that is very special. “Of the more than 50,000 known meteorites that have exploded on Earth, fewer than a dozen are like Ryugu,” said Associate Professor Alice Gorman, of the Flinders University† This shows how rare these meteorites, which look like fragile pieces of coal, are. “The terrestrial examples, however, are fragile,” Gorman continues. “They have been polluted by the weather and have absorbed moisture and other chemicals. The Ryugu monster is pure, so it can tell us so much more.”

More about carbonaceous chondrites

Carbonaceous chondrites are a rare and primitive type of rock that has a chemical composition very similar to that of the sun and the early solar nebula. Because they record geological activity during the early stages of our solar system, they provide insight into the history of their parent bodies. Occasionally, carbonaceous chondrites have already been found in meteorites that have fallen to Earth. In addition, they are among the oldest stones that can be found on our planet. It now appears that asteroid Ryugu also consists of carbonaceous chondrites. This suggests that the asteroid formed in the early years of the solar system.

What is particularly special about carbonaceous chondrites of type CI is that they contain “heavy elements” (ie elements other than hydrogen and helium) in almost the same amounts as the sun. But because the Ryugu material is still untouched and uncontaminated, it gives us a rare glimpse into the geological and chemical makeup of our solar system when it formed 4.6 billion years ago.

Most primitive

The researchers argue that Ryugu’s samples chemically represent the most primitive and pristine materials in the solar system yet analyzed in a lab, including the other CI meteorites found on Earth. “We have obtained samples from a number of planetary bodies before,” said Gretchen Benedix of the Curtin University† “But never from the most primitive material in the solar system.” And that means that the Ryugu samples will provide the clearest picture yet of the conditions that prevailed at the very beginning of the solar system.

Amino acids

In short, the pristine pieces of Ryugu will be able to help us learn more about the formation and early years of our solar system. But not only that. Carbonaceous chondrites of type CI contain abundant amino acids, which are often referred to as the ‘building blocks of life’. And so further analysis of the Ryugu samples could also help scientists better understand the origins of life.

Mission

The Japanese space probe Hayabusa2 was launched on December 4, 2014 and arrived at Ryugu in June 2018. After a year and a half of exciting research—think rover hopping around, a lander that made key measurements, and Hayabusa2’s own sampling of Ryugu—the probe said goodbye to the space rock last November and began its long journey back to Earth. In the end, Hayabusa2 traveled a total of about 5.2 billion kilometers.

Although the mission was already labeled a success, the analysis of the Ryugu samples now confirms it all the more. “This work is absolutely fascinating,” said Jonti Horner, professor of astrophysics at the University of Southern Queensland† “It shows how valuable samples from other celestial bodies are. By taking material from Ryugu home and analyzing it in the lab, astronomers can learn much more than just studying an asteroid from a distance.”