Due to their proximity to Earth, minimoons have attracted significant interest for exploration. Now, some scientists are contemplating utilizing these diminutive satellites to propel humanity deeper into the cosmos. In 2006, astronomers from the NASA-supported Catalina Sky Survey in Arizona stumbled upon a peculiar entity amidst the myriad of human-made satellites orbiting our planet. Upon closer examination, they concluded that this object wasn’t merely space debris but rather a natural satellite temporarily caught in an orbit alongside Earth, akin to the moon.
This “minimoon,” designated 2006 RH120, measured only a few meters in diameter. Unlike the actual moon, however, this cosmic entity was a transient companion to Earth, circling the planet for just a year before departing from its orbit. More than a decade later, scientists from the Catalina Sky Survey detected another minimoon (2020 CD3) — roughly the size of a small car — traversing Earth’s orbit before being expelled from the Earth-moon system’s gravitational influence in March 2020.
Due to their close proximity, minimoons have attracted significant scientific attention. Recently, some experts have viewed minimoons and other near-Earth asteroids as potential catalysts for advancing human exploration of space.
“We have yet to establish ourselves as an interplanetary species,” remarked Richard Binzel, a planetary sciences professor at the Massachusetts Institute of Technology. Minimoons could represent significant milestones “to pursue as we learn how humans can navigate interplanetary space and ultimately reach Mars.”
In September 2016, NASA launched the unmanned OSIRIS-REx spacecraft on a mission to retrieve a sample from the potentially hazardous asteroid Bennu. Seven years later, OSIRIS REx returned to Earth with a small piece of the 4.5 billion-year-old asteroid. The success of the OSIRIS-REx mission has spurred scientists to contemplate the next phases of near-Earth exploration. One concept involves utilizing nearby asteroids as stepping stones for missions to Mars.
While the Bennu retrieval marked a positive stride, Binzel noted that there might be superior targets for testing our capabilities to expand further into space. Minimoons, he explained, rank among the most accessible asteroids from Earth. These small celestial bodies exert minimal gravitational pull, requiring relatively little propulsion for spacecraft to travel from low Earth orbit to rendezvous with them.
Given their favorable properties, missions to minimoons could demand less fuel compared to journeys to other cosmic destinations. Binzel explained that it merely takes a minimal amount of fuel to depart from a Minimoon and return to Earth.
However, despite the promise of minimoon missions, their transient nature presents a challenge. Minimoons orbit Earth temporarily before being ejected, making it challenging to plan and execute missions before their departure.
Nonetheless, these missions hold promise for testing spacecraft technologies and mining operations in space. Near-Earth asteroids, including minimoons, could potentially serve as water-rich resources for creating rocket fuel essential for deep-space travel. While the technology and cost of accessing these resources remain significant hurdles, ongoing advancements in telescope technology offer hope for detecting more minimoons and unlocking the mysteries of our solar system.