Asteroid analysis reveals unexpected evidence of young ocean and carbonation

Asteroids are many things – killers of dinosaurs, archives of the early days of the solar system, Planetary Defense Objectives – But they’re not supposed to be watery worlds. right?

Well, at least not these days. But in the early days of the formation of the solar system, it was Ryugu – the diamond-shaped target of the Japan Aerospace Exploration Agency (JAXA) Hayabusa 2 Important – she had a small circumference inside her.

Before the asteroid was today, high-resolution isotope analysis shows it was part of an older, older parent before it exploded in a collision. But what is even more surprising is that within this small ocean, some dry silicates from the original native asteroid have managed to remain unchanged. A new paper from one of the organizing teams in Hayabusa Posted this month in natural astronomy They get what they show about the makeup of Ryugu’s father and the asteroids in the very early solar system.

what’s new – In December 2020, Hayabusa2 returned just over five grams of Ryugu after a six-year mission. Since the samples are a relatively limited number of small grains, each one was marked with its name and number. In this case, the team’s analysis was based on just one of these particles, C0009.

talk with inverseworld of cosmic chemistry isotopes Ming Chang Liu of UCLA found that C0009 was particularly interesting because it “distinguished itself by containing a small amount of anhydrous silicates”—that is, it contained water-unaffected, oxygen-rich minerals in the middle of a sample strongly altered by H2O.

Ryugu’s composition was greatly altered by the liquid water within her. Although formed in the cold depths of the outer solar system, water and carbon dioxide accumulate together in the protoliths that were Ryugu’s parents along with the short-lived radioactive isotopes. As those radioactive rocks heated the ice around them, Liu notes, “they would begin to float inside the mother body”—and over time would transform the silicates and pyroxene that made up Ryugu’s predecessor into water-bearing silicates.

Hence, the remaining anhydrous silicates give the team an idea of ​​what other materials in the early Solar System were like before they collided with the small ocean of Ryugu. The material looks like the oldest material that formed in the sun’s photosphere. The oxygen isotopes in the sample the team worked with show that the asteroid contains amoebic olivine and magnesium-rich chondrites that were incorporated directly from the solar nebula.

Moto Ito, a cosmic chemist at the Japan Agency for Marine Geosciences Technology and a member of the broader Phase II team, was the lead author—along with Liu and others—in Study of the original Ryugu particleswhich shows the ways in which CI meteorites on Earth have changed due to our more volatile environment.

talk with inverseIto notes that even if knowing the chemical composition “doesn’t tell us where the mother body formed,” it still “allows us to construct a kind of history of Ryugu, and how it formed in the outer solar system.”

why does it matter – This work comes from the efforts of the larger Phase Two organizing team. After Hayabusa2 crossed the ground to drop its payload, the five grams of samples it brought were divided into eight teams: six of them doing initial specific analysis – for chemical composition, stone and sandy materials, volatiles, solid and soluble organics – on materials, and two other large international teams They work to clarify the potential scientific impact of the samples.

In June, Liu and Ito’s senior team, from Okayama University in western Japan, published their interpretation of the samples. They found that Ryugu phyllosilicates are similar to those of CI chondrites, a rare and very primitive type of meteorite collected mostly in Antarctica.

But because they “may have been sitting there for decades, years, and ages before we picked them up,” Liu notes, “Earth has a very reactive atmosphere, so CI chondrites will interact with the atmosphere.” By comparison, samples from Hayabusa2 “are probably the most pristine chondrite material one can ever obtain.”

The survival of these elements from the Ryugu Protolith may be even more surprising in light of the work of some of the other teams. stone analysis team They published their preliminary results this month in Sciences, which included liquid water from Ryugu confined within a crystal. Because Ryugu picked up frozen carbon dioxide as well as water ice as it was forming, the liquid water in the sample was carbonated.

What’s next – some Ryugu context is already on its way to Earth. Last May, NASA Osiris Rex The spacecraft left the asteroid Bennu after shoveling perhaps half a pound of rock to begin its journey back to Earth. This was after OSIRIS-REx It unexpectedly created a 20-foot-wide hole in Bennu’s side The result is that it holds together with much less force than anyone expected.

Like Ryugu, Bennu is a relatively original carbon asteroid, although it is a different type: B-type asteroids like Bennu appear slightly bluer than Ryugu and their fellow C-type asteroids, which appear red. But regardless of its color, according to cosmologist Ito, finding similarly complex carbon components in the sample “will tell us about the distribution of organic components in the solar system.”

Although it answers questions about Ryugu’s makeup, this work also raises questions about how Ryugu fits into the scheme of more primitive asteroids and meteorites. According to Liu, the team believes that despite the different classes that have emerged to cover all the different chondrites found on Earth over the years, “those starting materials may have been very similar.” “We just want to be a little provocative, move the pot a little bit, and try to change the paradigm,” he added.