Asteroids are many things – killers of dinosaurs, archives from the early days of the solar system, Planetary Defense Objectives “But they shouldn’t be water worlds. 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 – she had a small circumference inside.
Before it became today’s asteroid, high-resolution isotope analysis shows it was part of an older parent before it exploded in a collision. But what’s even more surprising is that within this small ocean, some of the dried silicates from the original native asteroid have managed to remain unchanged. New article from one of the organizing teams at Hayabusa Posted this month in natural astronomy They are getting what they show about the formation of Ryugu’s father and the asteroids in the 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 was marked with its name and number. In this case, the team’s analysis was based on just one of those particles, C0009.
talk to me inverseThe world of cosmic chemistry isotopes Ming Chang Liu From the University of California, C0009 was found to be particularly interesting because it was “characterized by having a small amount of anhydrous silicates”—that is, it contained water-unaffected oxygen-rich minerals in the center of a sample strongly altered by H2O.
Ryugu’s makeup has been greatly altered due to the liquid water inside her. Although it formed in the cold depths of the outer solar system, water and carbon dioxide accumulated together in the protostones that were Ryugu’s parents, along with the short-lived radioactive isotopes. As these radioactive rocks heat the ice around them, Liu notes, “they will begin to float inside the mother’s body”—and over time will convert the silicates and pyroxenes that made up Ryugu’s predecessor into water-bearing silicates.
So the remaining anhydrous silicates give the team an idea of what other materials in the early Solar System looked like before they collided with the small ocean of Ryugu. The material looks like the oldest material that formed in the photosphere of the Sun. Oxygen isotopes in the sample the team worked with showed that the asteroid contained amoebic olivine and a magnesium-rich chondrite that were incorporated directly from the solar nebula.
Moto Ito, a cosmic chemist at the Japan Naval Geosciences Technology Agency 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 to me inverseIto points out that although knowing the chemical composition “does not tell us where the mother’s 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 Phase Two organizing team. After Hayabusa2 crossed Earth to drop its payload, the five grams of samples it brought were divided into eight teams: six doing specific primary analyzes – for chemical composition, stone and sandy materials, volatiles, solid and soluble organics – into the material, and two other large international teams working To clarify the potential scientific impact of the samples.
In June, Liu and Ito’s senior team at Okayama University in western Japan published their interpretation of the samples. They found that Ryugu phyllosilicates are similar to CI chondrites, a rare and very primitive type of meteorite collected mainly in Antarctica.
But because they “can be there for decades, years, and eons before we pick them up,” Liu notes, “Earth has a very reactive atmosphere, so the CI gondrones will interact with the atmosphere.” By comparison, the Hayabusa2 samples “are probably the purest chondrite you can get.”
The survival of the elements of the Ryugu Protolith might be even more surprising given the work of some of the other teams. stone analysis team Its preliminary results were published this month in Sciences, which included Ryugu liquid water trapped within a crystal. When the Ryugu ignited frozen carbon dioxide as well as water ice as they were forming, the liquid water in the sample was carbonated.
What’s to come next – some Ryugu context is already on its way to Earth. Last May, NASA Osiris King The spacecraft left the asteroid Bennu after removing perhaps a pound of rock to begin its journey back to Earth. This was after OSIRIS-REx He unexpectedly created a 20-foot-wide pit in Benno’s side. The result is that it holds together with much less force than anyone expected.
Like Ryugu, Bennu is a relatively unique carbonaceous asteroid, albeit of a different type: B-type asteroids like Bennu appear slightly bluer than Ryugu and his C-type companions, which appear red. But regardless of its 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 the formation of Ryugu, 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 types of chondrites found on Earth over the years, “these early 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.
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