Researchers are using space rocks to uncover some of the mysteries of the solar system. These rocks may hold important clues that help us to better understand the history of our solar system. One significant discovery has already been made through the OSIRIS REx mission, which found water and carbon on the asteroid Bennu. These two elements are important building blocks for life on Earth and can help us learn more about the origins of our planet. According to Richard Binzel, a planetary sciences professor at MIT, minimoons – small celestial bodies that have orbits partially governed by Earth and partially by other solar system bodies – may be ideal for studying the history of the solar system.
“[Minimoons] probably have had a bit of a pinball experience in the inner solar system, being ricocheted around and tugged on by the different planets,” Binzel told Live Science. “They finally found themselves in a way that they got tugged into a somewhat circular orbit near the Earth.”
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Minimoons are small moons that orbit relatively close to the Earth. Compared to asteroids like Bennu, they require less time and fuel to reach and sample due to their proximity to Earth. The origin of minimoons is still uncertain, but scientists believe they came from the main asteroid belt located between Mars and Jupiter.
Near-Earth asteroids from this region, such as Bennu or a minimoon, are “like time capsules,” Paul Abell, chief scientist for small body exploration at NASA, told Live Science. “They give us indications of what the early solar system was like [and] what the conditions were.”
In 2019, the Japan Aerospace Exploration Agency (JAXA) successfully gathered samples from the diamond-shaped asteroid Ryugu, which is more than 200 million miles (322 million kilometers) away from Earth. The analysis of the samples revealed that the space rock contains stardust that existed before our solar system, as well as “prebiotic organics” – including several amino acids that are used by living beings to build proteins, the building blocks of things like hair and muscles.
Collecting samples from minimoons could significantly improve current asteroid research, as scientists mostly rely on studying fragments of asteroids that have fallen to Earth in the form of meteorites. However, these meteorites can be difficult to analyze depending on their condition. According to Abell, studying minimoons could potentially solve this problem.
“When we have a meteorite falling on Earth, it’s already contaminated” by moisture and gasses in Earth’s atmosphere, he said. “When you’re talking about organic molecules and water — more volatile type materials — going to the source and figuring out what’s there is really important. That’s why we’d like to do these sample return missions, like OSIRIS REx.”
In September, the OSIRIS-REx spacecraft successfully delivered the collected sample of Bennu to Earth. This marked NASA’s first successful mission in collecting samples from an asteroid. The spacecraft is now on its way to explore the asteroid Apophis. It is expected to reach the asteroid in 2029, when it passes within 19,800 miles (31,865 km) of our planet.
NASA will continue to study the rocks and dust within Bennu over the next decade because “the bounty of carbon-rich material and the abundant presence of water-bearing clay minerals are just the tip of the cosmic iceberg,” Dante Lauretta, OSIRIS-REx’s principal investigator, said at a news conference in October.
Scientists planning near-Earth exploration are inspired by the success of the OSIRIS-REx mission and may consider a minimoon as the next destination.