Asteroid analysis reveals unexpected evidence of ocean youth and carbonation

Asteroids are many things – killers of dinosaurs, records from the early days of the solar system, Planetary Defense Objectives – But they must not be watery worlds. Turn right?

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

Before the asteroid was there today, high-resolution isotope analysis shows that it belonged to an older, older parent before it exploded on impact. But what is even more surprising is that in this small ocean, some dry silicates from the original native asteroid have managed to remain unchanged. New newspaper from one of the organizing teams in Hayabusa Posted in this month natural astronomy They are getting what they show about the composition 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. Because the samples included a relatively small number of small grains, each was given a name and a number. In this case, the team’s analysis was based on just one of these particles, C0009.

to talk with inverseThe world of cosmic chemistry isotopes Ming Chang Liu of the University of California, C0009 was found to be particularly interesting because it is “characteristic of containing a small amount of anhydrous silicates”—that is, it contains unaffected, oxygen-rich minerals in the center of a sample strongly altered by H2O.

The composition of Ryugu has been significantly changed due to the liquid water in it. Although formed in the cold depths of the outer solar system, water and carbon dioxide accumulate in the protostones that were Ryugu’s parents, along with short-lived radioactive isotopes. As those radioactive rocks heat the ice around them, Liu notes, “they will float in the parent body”—and over time, the silicates and pyroxene that were Ryugu’s predecessor will turn into hydrated silicates.

Therefore, the remaining anhydrous silicates give the team an idea of ​​what other materials in the early Solar System looked like before colliding with the small ocean of Ryugu. The material is similar to the oldest material formed in the photosphere of the Sun. The oxygen isotopes in the team’s sample show that the asteroid contains amoebic olivine and a magnesium-rich chondrite taken 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 particlesIt shows the ways in which CI meteorites on Earth have changed as a result of our more volatile environment.

to talk with inverseIto points out that even if knowing its chemical composition “doesn’t tell us where the mother body formed,” it still “allows us to build 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 organizational team for Phase Two. After Hayabusa2 crossed the Earth to drop its payload, the five-gram samples it brought with it were divided into eight teams: six of them did specific preliminary analyzes — for chemical composition, rock and sandy materials, volatiles, solids, and soluble materials. Materials, and two other major international teams. They are working 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 the Ryugu silicate is similar to that of the CI chondrite, a very rare and primitive type of meteorite usually collected in Antarctica.

But since they “may have sat for decades, years, and centuries before we caught them,” notes Liu, “Earth has a very reactive atmosphere, so CI chondrites will interact with the atmosphere.” By comparison, samples from Hayabusa2 “are probably the most primitive chondrites you can ever get.”

The persistence of these elements from the Ryugu Protolith is perhaps even more surprising in light of the work of some of the other teams. stone analysis team Its preliminary results were published this month in Sciences, including liquid water from Ryugu enclosed in a crystal. Because Ryugu picked up frozen carbon dioxide and water ice as they formed, the liquid water in the sample became carbonated.

What is now – Ryugu’s 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 As a result, it reacts much less aggressively 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 are shown in red. But regardless of color, according to cosmologist Ito, finding similar complex carbon components in the sample “will tell us about the distribution of organic components in the solar system.”

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