Rubin Observatory Could Find More of Earth's Mini-Moons

Grigori Fedorets, a researcher at the University of Helsinki, presented estimates for mini-moon discoveries at the 2026 Europlanet Science Congress. He expects the Vera C. Rubin Observatory’s Legacy Survey of Space and Time to detect about one mini-moon every two years, with a planned alert-screening system potentially increasing that rate.

Key details

• Fedorets estimates a typical mini-moon capture lasts about nine months and spans roughly three orbits around Earth.
• Models indicate the largest mini-moon present at a given time usually measures about 75 centimeters across; an object around 3 meters wide may be captured every 10 to 20 years.
• The Vera C. Rubin Observatory’s Legacy Survey of Space and Time is planned to run for 10 years.
• Two mini-moons identified in the report, 2006 RH120 and 2020 CD3, were discovered by the Catalina Sky Survey.

Fedorets estimates that a planned alert-screening system could raise the discovery rate to two or three mini-moons per year.

Why it matters

More detections could help researchers compare models of near-Earth objects measuring 1 to 10 meters with estimates drawn from observed atmospheric fireballs. Scientists have also proposed CubeSat demonstrations and possible sample-return missions to study mini-moons. Their proximity to Earth and low relative speeds may reduce the energy needed for a spacecraft to reach them.

What happens next

Fedorets said the survey’s planned alert-screening system could raise the estimated discovery rate to two or three mini-moons per year. The material gives no confirmed mission schedule or approved sampling plan.