Scientists reveal doughnut-shaped early solar system based on iron meteorite analysis

Science Alert carries an article about new research which suggests that the early Solar System once had a toroidal, or doughnut-shaped, structure before evolving into its familiar flattened disk form, Caliber.Az reprints the article.

A recent study suggests that the early Solar System was once toroidal, or doughnut-shaped, before flattening into a disk, according to scientists examining iron meteorites from the outer Solar System. This discovery, led by planetary scientist Bidong Zhang from the University of California Los Angeles, challenges traditional views and offers insights into the formation of planetary systems.

The research reveals that the initial distribution of dust and rocks in the Solar System had more in common with a doughnut than a pancake. This conclusion is drawn from the composition of iron meteorites rich in refractory metals like platinum and iridium, which are typically formed close to a star in very hot environments. Surprisingly, these meteorites originated from the outer Solar System, indicating that they must have formed near the Sun and migrated outward.

Zhang's team conducted modeling that showed such migration would be difficult if the protoplanetary disk were flat. Instead, a toroidal shape would have facilitated the movement of these metal-rich objects to the outer regions. This doughnut-like structure would later transition into a flat disk as the Solar System cooled and planets began to form.

The study suggests that once Jupiter formed, it likely created a gap in the disk that trapped the metals in the outer regions, preventing them from falling into the Sun. These metals were then incorporated into outer-disk asteroids, explaining why meteorites from this region, such as carbonaceous chondrites and carbonaceous-type iron meteorites, have higher iridium and platinum contents than those from the inner disk.

"Once Jupiter formed, it very likely opened a physical gap that trapped the iridium and platinum metals in the outer disk and prevented them from falling into the Sun," Zhang explains. "These metals were later incorporated into asteroids that formed in the outer disk. This explains why meteorites formed in the outer disk have much higher iridium and platinum contents than their inner-disk peers."

This discovery not only provides new insights into the early formation of our Solar System but also offers valuable information for interpreting the development of other emerging planetary systems, helping to determine the sequence of their assembly.