The solar system’s first solids formed in a rush

April 22, 2026

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The solar system’s first solids formed in a rush

Rather than slowly condensing over millions of years, the first building blocks of Earth and other planets may have formed rapidly in a chaotic disk at the dawn of the solar system

By Javier Barbuzano edited by Lee Billings

An artist’s concept shows the inner regions of a protoplanetary disk around a young star. Planets grow within the disk from smaller building blocks of material that rain out of the disk’s gas as it cools.

NASA/ESA/CSA/Joseph Olmsted/STScI

Some 4.6 billion years ago, when the solar system was born from a vast cloud that collapsed to form the sun and a surrounding disk of whirling gas, no planets yet orbited our star. Back then, besides stardust, no solid materials at all drifted through this natal disk. Only as the disk cooled did mineral grains condense from the gas to become the building blocks of space rocks that would eventually form Earth and other planets.

Scientists have long suspected this was a relatively peaceful process, with showers of primordial solids slowly raining out from the disk as it cooled over millions of years. Now, however, a study published today in Nature is challenging this sedate view, suggesting instead that the solar system’s first solids stormed into being much faster from sudden temperature shifts in the disk’s turbulent maelstrom.

“This is a real change of paradigm,” says Alessandro Morbidelli, an astronomer at the Côte d’Azur Observatory in France, who wasn’t involved with the new study. “It is a good idea, and the result has been quite surprising.”

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The notion of a placid start for the solar system’s solids has prevailed for the past half-century. In the late 1960s researchers studying meteorites discovered that some held small granules called calcium-aluminum-rich inclusions (CAIs). These amalgams of minerals are considered the first solids of the solar system, and they formed when the disk’s temperature dropped just enough for them to condense out of the cooling gas. Based on the composition of CAIs, researchers assumed that their condensation reactions occurred across millions of years. That would allow sufficient time for these reactions to reach chemical equilibrium, meaning that at each successive stage of the disk’s chemical evolution, the distribution of elements in gaseous and mineral phases would stabilize.

But this model, known as equilibrium condensation, has limitations. It cannot explain clear composition variations in the most primitive types of meteorites, called chondrites. Chondrites are divided into three families—ordinary, enstatite and carbonaceous—with the key difference being how oxidized their iron-bearing minerals are, much like the difference between a shiny unoxidized iron nail and one that’s rusty from heavy oxidation. Enstatite chondrites are the least oxidized chondrites, carbonaceous ones are the most oxidized, and ordinary chondrites have an intermediate oxidation level.

Experts have long assumed this disparity among the chondrites means each variety originated in a different, chemically distinct area of the solar disk, but the details for how exactly this could yield the three known types have remained murky.

Now a team led by Sébastien Charnoz, a planetary scientist at the Paris Institute of Planetary Physics, offers a radically different explanation that was derived from computer simulations that modeled how minerals condense from a chemically uniform disk at a wide range of pressures and cooling rates. The simulations suggest that, if the disk was turbulent instead of placid, parts of it could cool so quickly that the resulting chemistry wouldn’t be in equilibrium at all. Rather than elements raining out as minerals in stately succession because of gradual cooling, the rapid plunge in temperature would outpace chemical reaction rates in the disk. This would leave some elements temporarily trapped in gaseous form, allowing more mixing and the simultaneous emergence of multiple minerals. Most importantly, Charnoz and his colleagues’ results clustered into three mineralogical families that closely resemble the composition of the three main chondrite types.

To better explain these dizzyingly complex processes, Charnoz compares the minerals raining out of a cooling disk to hungry diners at a dinner table. When cooling is slow, the earliest minerals to condense “eat” elements from the gaseous disk, sequestering and sweeping them from the “table” so that subsequent minerals that form at l