AI Insight
Earth possesses a group of small rocky objects called "co-orbitals" that share the same orbital period around the Sun as Earth, maintaining a 1:1 mean motion resonance. The origin of these objects has been debated, with two competing hypotheses: they either migrated from the main asteroid belt between Mars and Jupiter, or they are fragments ejected from the Moon. A new study published in Icarus by researchers Elisa Alessi and Robert Jedicke presents evidence favoring the asteroid belt as the more probable source, though a definitive answer is expected from an upcoming spacecraft mission.
Why it matters
Understanding the origin of Earth's co-orbital companions helps reconstruct the history of the inner Solar System and assess the potential risk or resource value of near-Earth objects. It also has implications for understanding how material is transferred between planetary bodies, including the Moon and Earth.
Earth has a group of cosmic stalkers. Known as “co-orbitals,” these small bits of rock have a 1:1 mean motion resonance with Earth. Basically, they take the exact same amount of time to orbit the sun as we do. Astronomers have long believed these objects wandered in from the main asteroid belt between Mars and Jupiter, but recent spectral analysis suggests they better match the space-weathered lunar silicates that make up the moon’s surface. As such, there has been an ongoing debate about whether these cosmic stalkers are actually visitors from the belt or blasted pieces of the moon. A new study, published in Icarus, from researchers Elisa Alessi and Robert Jedicke provides strong hints that the belt is the more likely source—but pretty soon we’ll get a definitive answer from a spacecraft.
Source: Is Earth's constant companion a stray asteroid or a chunk of the moon?