Our solar system is estimated to be 4.57 billion years old. According to research of ancient meteorites, minerals were produced as far back as 4.5 billion years ago by chemical reactions with water.
UCLA space scientists and colleagues are using mineral samples from the Ryugu asteroid, which Japan’s Hayabusa2 spacecraft collected, to better understand the chemical makeup of our solar system when it was in its infancy, more than 4.5 billion years ago.
In a new study, scientists used isotope analysis. They found that the asteroid’s carbonate minerals were crystallized by reactions with water, originally added to the asteroid as ice in the still-forming solar system, and then heated to liquid.
They argue that these carbonates evolved exceptionally early in the solar system’s history, within the first 1.8 million years, and serve as a record of the temperature and chemical composition of the asteroid’s aqueous fluid at that time.
Study co-author Kevin McKeegan, a distinguished professor of earth, planetary and space sciences at UCLA, said: “Rocky, carbon-rich Ryugu is the first C-type (C stands for “carbonaceous”) asteroid from which samples have been collected and studied. What makes Ryugu special is that, unlike meteorites, it has had no potentially contaminating contact with Earth. By analyzing the chemical fingerprints in the samples, scientists can get a sense of not only how Ryugu originated, but also where.”
“The Ryugu samples tell us that the asteroid and similar objects formed relatively quickly in the outer solar system, beyond the condensation fronts of water and carbon dioxide ice, probably as small bodies.”
Ryugu, or a progenitor asteroid from which it may have split off, grew as a relatively small object, possibly less than 20 kilometers (12.5 mi) in diameter. The researchers’ research found that Ryugu’s carbonates formed several million years earlier than previously believed.
The results surprised researchers, as most models of asteroid accretion would predict assembly over longer periods of time, resulting in the formation of bodies at least 50 kilometers (more than 30 miles) in diameter that predict the evolution of collisions over the long history of asteroids. better survive the solar energy. system.
Researchers noted, “any larger asteroid formed very early in the solar system would have been heated to high temperatures by the decay of large amounts of aluminum-26, a radioactive nuclide, resulting in rock melting throughout the asteroid’s interior, along with chemical differentiation, such as the separation of metal and silicate.”
Ryugu shows no evidence for this, and the chemical and mineralogical compositions are similar to those found in the most chemically primitive meteorites, the so-called CI chondrites, which are also believed to have formed in the outer solar system.
McKeegan said: “ongoing research on the Ryugu materials will continue to open a window into the formation of the solar system’s planets, including Earth.”
“By improving our understanding of volatile and carbon-rich asteroids, we can answer important questions in astrobiology, for example the likelihood that rocky planets have access to a source of prebiotic materials.”
To date, for the carbonates in the Ryugu samples, the team has extended the methodology developed at UCLA to another “short-lived” radioactive decay system involving the isotope manganese-53, which was present in Ryugu.
- McCain, K. A., Matsuda, N., Liu, M. C. et al. Early fluid activity on Ryugu inferred by isotope analyzes of carbonates and magnetite. Nat Astron (2023). DOI: 10.1038/s41550-022-01863-0