Asteroid Ryugu Formed at the Solar System's Dawn
New research suggests Ryugu predates chondrules, marking it as a first-generation planetary building block.
1Ancient Solar System Origins
Research published in Science indicates that asteroid Ryugu formed during the earliest stages of the solar system. Unlike most carbon-rich meteorites, Ryugu lacks chondrules, which are millimeter-sized molten droplets common in other space rocks. This suggests the asteroid originated as part of the very first generation of planetary precursors.
2Dating Through Mineral Analysis
Scientists determined the age of Ryugu by analyzing dolomite minerals within samples collected by Japan's Hayabusa2 spacecraft. They measured radioactive manganese decaying into chromium to establish a timeline. Additionally, the team examined oxygen isotope ratios to calculate the temperatures at which these minerals originally crystallized billions of years ago.
3Thermal History and Formation
The study identified a specific grain containing dolomite that formed at approximately 92 degrees Celsius around 4.565 billion years ago. According to NASA researcher Ann Nguyen, the heat required for this mineral formation originated within the asteroid's parent body, necessitating a heating process lasting at least one million years.
4Early Planetesimal Development
Simulations suggest that Ryugu coalesced less than two million years after the first solids appeared in the solar system. This timeline places its formation before the widespread emergence of chondrules. Consequently, Ryugu serves as a rare, preserved remnant of the raw ingredients present during the initial wave of planet building.
5Waves of Planetary Construction
The findings support theories that solar system bodies were constructed in distinct waves. Fine dust, ice, and organic matter clumped together around the newborn sun to form larger objects. If the current data is accurate, Ryugu represents a leftover from that first generation, providing insight into the system's rapid early evolution.
6Scientific Community Perspectives
Myriam Telus, a planetary scientist at UC Santa Cruz, describes the work as high-impact research for the field. However, she notes that other dating methods have previously placed chondrule formation earlier in history. She emphasizes that the manganese-chromium dating system used in this study requires further refinement to ensure absolute accuracy.
7Future Comparative Research
Researchers plan to apply these same analytical methods to samples from asteroid Bennu, collected by NASA's OSIRIS-REx mission. By comparing the mineral composition and age of Bennu with Ryugu, scientists hope to determine if the two asteroids share a common parent body or if they are siblings from the same era.
8Significance of Early Samples
Studying these ancient asteroids allows scientists to reconstruct the conditions present at the dawn of our solar system. By analyzing these raw materials, researchers gain a clearer understanding of how planetary building blocks evolved. This work remains essential for refining models of how the sun and its surrounding planets originally formed.
Original article: Scientific American — Asteroid Ryugu Formed at the Solar System's Dawn