Recent simulations suggest that smaller rocky exoplanets are more likely to host large moons, shedding light on the formation of Earth’s moon and potential exomoons around other planets in the universe.

Scientists have long debated the origins of Earth’s moon, theorizing that it formed from debris after a collision with a Mars-size planetesimal called Theia. This impact created a ring of material around Earth that eventually coalesced to form the moon we see today.

However, the specifics of moon formation remain a topic of intense discussion. Factors such as the angle and velocity of the impact can significantly influence the outcome. For instance, a more energetic collision would result in a moon-forming disk dominated by vapor, while a less energetic impact would produce a disk dominated by silicate rock.

New research delves into the concept of ‘streaming instability,’ which plays a crucial role in the accretion of small particles in a vapor-rich disk around a planet. This process leads to the formation of moonlets of varying sizes, ranging from small to substantial dimensions.

While streaming instabilities are essential in models of planet formation, simulations conducted by a team led by Miki Nakajima at the University of Rochester suggest potential challenges for moon survival. The moonlets generated by streaming instabilities may not be sufficiently large to maintain their orbit around a planet, eventually succumbing to drag forces from friction with surrounding vapor.

These findings have significant implications for the search for exomoons beyond our solar system. The study indicates that exomoons are more likely to be discovered around smaller rocky exoplanets, offering valuable insights into the cosmic phenomena of moon formation.