Mineral samples taken from the Ryugu asteroid by the Japan’s Hayabusa2 spacecraft are helping UCLA researchers as well as colleagues better understand the chemical structure of our world as it existed in its infancy, over 4.5 billion years ago.
In a study published in Nature Astronomy, researchers found that carbonate minerals from the asteroid had been crystallized by way of reactions with water that initially accreted as ice on the asteroid in the still-forming solar system and then warmed into a liquid. They state these carbonates developed quite early inside the very first 1.8 million years of the solar system’s existence, and they keep a history of the temperature as well as structure of the asteroid aqueous fluid, because it existed in that time.
Ryugu, a rocky carbon-rich asteroid, is the very first C-type (C for carbonaceous) asteroid from which samples are collected and examined, said study co-author Kevin McKeegan, a distinguished professor of Earth, planetary and space sciences at UCLA. He stated that Ryugu’s uniqueness is, as opposed to meteorites, it hasn’t had possibly contaminating contact with the Earth. Experts could produce a photograph of exactly how Ryugu formed, and exactly where, by looking at the chemical fingerprints in the samples.
“The Ryugu samples reveal that the asteroid along with related objects fairly quickly formed in the outer solar system over the condensation fronts of water as well as co2 ices, possibly as little bodies,” McKeegan said.
Their results suggest Ryugu’s carbonates formed a number of thousand years earlier than previously believed, and also they suggest that Ryugu accreted as a relatively small object, most likely under 20 kilometers (12.5 miles) in diameter.
McKeegan pointed out the majority of models of asteroid accretion will anticipate assembly over much longer periods, leading to the development of bodies of more than 50 kilometers (more than 30 miles) diameter which could better survive collisional evolution with the long history of the solar system.
Although Ryugu is just about one kilometer across, due to collisions and reassembly all through its history, it’s incredibly unlikely it was actually a big asteroid, the scientists said. Any bigger asteroid developed quite early on in the solar system would have been heated to high temperatures by the decay of significant amounts of aluminum-26, a radioactive nuclide, leading to the melting of rock throughout the asteroid’s interior together with chemical differentiation such as the segregation of silicate and metal.
Ryugu has absolutely no evidence of this, and its chemical and mineralogical compositions are comparable to those in the most chemically primitive meteorites, the so called CI chondrites, which can also be believed to have formed in the outer solar system.
McKeegan pointed out research on Ryugu components is going to continue to open a window onto the creation of planets in the solar system, such as the planet.
“Improving our knowledge of carbon-rich and volatile asteroids will help us deal with important concerns in astrobiology, for instance the chance that rocky planets can access a supply of prebiotic materials,” he said.
Currently the carbonates in the Ryugu samples, the team extended the method developed at UCLA for an alternative “short-lived” radioactive decay structure involving the isotope manganese-53, that had been contained in the Ryugu.
The research was co-led by Kaitlyn McCain, a UCLA doctoral student at time of re-search who today works for NASA’s Johnson Space Center in Houston, and postdoctoral researcher Nozomi Matsuda, who works in the ion microprobe lab of the UCLA’s Department of Earth, Planetary and Space Sciences.
The paper’s additional co-authors include researchers from the Kochi team headed by Motoo Ito from the Phase 2 curation staff in Japan. This team is responsible for picking out particles from the regolith sample taken from the Ryugu asteroid and examining their chemical and petrological attributes using synchronised microanalytical methods.
DOI: 10.1038/s41550-022-01863-0
