The formation of the inner solar system may not align with previous scientific beliefs. Traditionally, researchers posited that rocky planets emerged from a singular disc of dust and debris originating from the early solar system. However, groundbreaking new simulations indicate the possible existence of two distinct disks.

Models relying on a single disk or ring of material surrounding the young Sun tend to fall short in replicating several observable features of our solar system. For instance, Earth’s unique rock composition suggests a blend of two different types, which raises questions about their originating from a singular ring. Moreover, single-ring models often render Mercury and Mars disproportionately large while placing Venus and Earth too closely together, leading to composition similarities between Earth and Mars that seem out of place.

Bill Bottke, along with his team at Colorado’s Southwest Research Institute, conducted a series of sophisticated simulations exploring how planets could evolve from a shared reservoir of material. Yet they faced persistent challenges.

“For six months, we tried different simulations without success,” Bottke explained during a recent presentation at the Lunar and Planetary Science Conference held in Texas on March 16th. “In a moment of desperation, we considered testing a second reservoir and discovered that this approach yielded a viable model for creating terrestrial planets, while addressing many of the outstanding concerns.”

The optimal model proposed involved two separate disks: one situated about half the current distance from the Sun to Earth and the other approximately 1.7 times that distance. The simulation resulted in planets of proper size and distance.

This theory also aligns with the compositions of the Earth, Moon, and Mars. “We believe Earth predominantly formed from material sourced from the inner solar system, with only a minor contribution from outside,” noted Jan Hermann, who delivered a related presentation the same day at the Max Planck Institute for Solar System Research in Germany. In contrast, Mars appears to have formed mainly from the outer disk, explaining the contrasting compositions of the two planets.

Nonetheless, some researchers express concern that this model relies on very specific initial conditions that may not be entirely understood. “Small alterations in the shape of the disk can significantly affect the outcome of where terrestrial planets are positioned,” Bottke cautioned.

Current efforts are focused on refining the model and exploring additional factors that may influence solar system formation. “We’re investing considerable computational resources to examine every logical possibility,” Bottke indicated. If successful, this new perspective could illuminate various solar system enigmas, from anomalous asteroids to mysterious lunar rocks.