After a six-year voyage, a bold spaceship called Hayabusa2 returned to Earth’s atmosphere in late 2020 and landed deep in the Australian outback. When researchers from Japan’s JAXA space agency discovered it, they found its valuable payload sealed and intact: a handful of dirt that Hayabusa2 managed to scrape off the surface of an accelerating asteroid.
Now scientists have begun to announce the first results of the analysis of this exceptional sample. What they discovered suggests that this asteroid is part of the same thing that merged into our sun four and a half billion years ago.
“Before, we only had a handful of these rocks to study, and they were all meteorites that fell to Earth and were stored in museums for decades to centuries, which changed their composition,” said geochemist Nicholas Dofas, one of three researchers’ universities. from Chicago, who worked with a Japanese-led international team of scientists to analyze the fragments. “Having virgin samples from space is just amazing. They’re witnessing parts of the solar system that we haven’t studied otherwise.”
In 2018, Hayabusa2 landed on top of a moving asteroid named Ryugu and collected particles above and below its surface. After spending a year and a half in orbit around the asteroid, he returned to Earth with a sealed capsule containing about five grams of dust and rocks. Scientists around the world are looking forward to the unique test – one that can help redefine our understanding of how planets evolve and how our solar system formed.
Scientists are particularly excited because these particles would never have reached Earth without the spacecraft’s protective barrier.
“Usually all we get when we study asteroids are pieces that are big enough to reach the earth like meteorites,” said Chicago geochemist Andrew M. Davis, another member of the analysis team. “If you take this handful and release it into the atmosphere, it will burn. You will lose it and a lot of evidence for the history of this asteroid will go with it.
“We really haven’t had a rehearsal like this before. It’s spectacular.”
Davis, Daufas, and Chicago colleague Reika Yokochi are part of a team assembled to help Japanese researchers analyze samples. Each part of the contents of the capsule is studied strictly. Yokochi is part of a team that analyzes the gases that have been trapped in the capsule or in the dirt. Daufas and Davis are part of a team studying the chemical and isotopic composition of grains to uncover their history.
The first compilation of these results reported in science on June 9 reveal Ryugu makeup.
The rock is similar to a class of meteorites known as “Ivuna-type carbon chondrites.” These rocks have a similar chemical composition to that we measure from the sun, and are thought to date from the very beginning of the solar system approximately four and a half billion years ago – before the formation of the sun, moon and earth. [should Moon be capitalized to distinguish it from other moons?]
All that existed then was a gigantic, swirling cloud of gas. Scientists believe that most of this gas was drawn to the center and formed the star we know as the sun. As the remnants of this gas expand into a disk and cool, it turns into rocks that still float around the solar system today; it seems Ryugu may be one of them.
The scientists said the fragments showed signs of being soaked in water at some point. “We have to imagine a collection of ice and dust floating in space that turned into a giant muddy ball when the ice was melted by nuclear energy from the decay of radioactive elements present in the asteroid when it formed,” Dofas said. But surprisingly, today the rock itself looks relatively dry.
Using radioisotope dating, they estimated that Ryugu was altered by the circulation of water only about five million years after the formation of the solar system.
These findings are particularly interesting to researchers because they hint at similar conditions of formation between comets and some asteroids such as Ryugu.
“By examining these samples, we can limit the temperatures and conditions that must have occurred during their lifetime and try to understand what happened,” Yokochi explained.
She compared the process to trying to figure out how the soup was made, but only to the end result, not the recipe: “We can take the soup and separate the ingredients and try to understand from their conditions how hot it is and in what order.”
Scientists have noted that a percentage of the find will be set aside so that we can analyze it in the future with more advanced technology – just as we did with the Apollo lunar samples.
“After we received lunar samples from Apollo 50 years ago, our ideas about how the moon formed completely changed,” Davis said. “We are still learning new things from them because our tools and technologies are advanced.
“The same will apply to these samples. This is a gift he continues to give.”
This mission is the first of several international missions that will return samples from another asteroid named Bennu, as well as unexplored areas of our moon, Mars and the moon of Mars Phobos. All this should happen in the next 10 to 20 years.
“It was very much on the radar for the public and some decision-makers, but we are entering a new era of exploring the planet that is unprecedented in history,” Dofas said. “Our children and grandchildren will see returned fragments of asteroids, Mars and hopefully other planets when they visit museums.”