Chondrules are tiny, round droplets of once-molten rock found in many meteorites. They formed when silicate liquids cooled and hardened in space, but how exactly they came to be has puzzled scientists for years.
About 4.5 billion years ago, Jupiter grew rapidly, becoming a gravitational giant. Its pull stirred up chaos among nearby space rocks and icy bodies, called planetesimals, causing them to crash into each other at incredible speeds. These violent impacts melted the debris, creating floating droplets of molten rock: chondrules.
Now, researchers from Nagoya University and INAF have cracked the mystery. By studying the size and cooling patterns of chondrules, they discovered that water inside the crashing planetesimals played a key role in shaping them. This not only explains what we see in meteorites today, but it also helps pinpoint when Jupiter formed.
Co-lead author Professor Sin-iti Sirono from Nagoya University’s Graduate School of Earth and Environmental Sciences explained, “When planetesimals collided with each other, water instantly vaporized into expanding steam. This acted like tiny explosions and broke apart the molten silicate rock into the tiny droplets we see in meteorites today.”
“Previous formation theories couldn’t explain chondrule characteristics without requiring particular conditions, while this model requires conditions that naturally occurred in the early solar system when Jupiter was born.”
By developing and using computer simulations of Jupiter’s growth, the researchers tracked how its gravity caused high-speed collisions between rocky and water-rich planetesimals in the early solar system.
“We compared the characteristics and abundance of simulated chondrules to meteorite data and found that the model spontaneously generated realistic chondrules. The model also shows that chondrule production coincides with Jupiter’s intense accumulation of nebular gas to reach its massive size. As meteorite data tell us that peak chondrule formation took place 1.8 million years after the solar system began, this is also the time at which Jupiter was born.”
This study helps us better understand how our solar system came to be. When Jupiter formed, it sparked the creation of molten rock droplets called chondrules. But that event alone was too short to explain why meteorites contain chondrules from many different time periods.
The likely reason? Other giant planets, like Saturn, also caused chondrule formation when they were born. Each planetary arrival added a new wave of molten droplets to the mix.
By examining chondrules of different ages, scientists can map out the birth order of the planets and see how the solar system evolved. Even more exciting, this research hints that similar violent processes may happen around other stars, giving us clues about how other planetary systems might form.
Journal Reference:
- Sirono, Si., Turrini, D. Chondrule formation by collisions of planetesimals containing volatiles triggered by Jupiter’s formation. Sci Rep 15, 30919 (2025). DOI: 10.1038/s41598-025-12643-x