On October 20, 2020, a robot carefully scooped up 121.6 grams of the most expensive dirt in the solar system.
That robot, a NASA spacecraft called OSIRIS-REx, had spent two years en route to its rendezvous with the near-earth asteroid Bennu and two more observing it. Its 1.16-billion-dollar mission: Recover a sample from Bennu’s strange surface of loosely-bound space pebbles and return it to Earth. It succeeded, and on September 24, 2023, OSIRIS-REx dropped its carefully-packed sample capsule through Earth’s atmosphere and into the waiting arms of eager scientists.
Bennu and a handful of special asteroids like it are ancient objects, leftovers from the very earliest moments of planet formation in our solar system. The sample OSIRIS-REx returned contains minerals that formed in water and a dazzling diversity of organic compounds, which contain carbon.
On our planet, organics are the stuff of life. But they’re the stuff of space, too—astronomers and planetary scientists are finding organics practically everywhere they look, from cold clouds of interstellar dust to icy moons to asteroids like Bennu. Sample return has revealed that Bennu sports a practical zoo of organics, including amino acids and other simple molecules that link together in life to form complex biological machinery. And just last month, scientists discovered sugars in Bennu that play vital roles in biology. Some scientists think these clues are a hint that the raw materials of life on Earth may have fallen from the heavens.
OSIRIS-REx isn’t the only asteroid sample return mission. It comes on the heels of a Japanese effort, Hayabusa2, which returned 5.4 grams of rock from another ancient asteroid called Ryugu in 2020. By retrieving pristine specimens from these cosmic time capsules, scientists are revealing new details about the history of our own planet—and about where and how life might have emerged in the solar system.
Some of our best clues about the earliest days of the solar system come from meteorites, or space rocks that fell to Earth. Less than five percent of meteorites belong to a special class called carbonaceous chondrites, which are practically as old as the solar system itself. They contain water bound up in rock and diverse organic molecules, from amino acids to simple components of DNA. Carbonaceous chondrites are like a snapshot of the chemical processes in the early solar system that set the stage for the origin of life.
“That is why we have used chondritic meteorites as a key to understand solar system formation and planet formation,” says cosmochemist Shogo Tachibana of the University of Tokyo, who led sample analysis for the Hayabusa2 mission. “But meteorites are always subject to terrestrial contamination.”
(Yahoo news)
