Samples brought back to Earth from the asteroid Bennu by NASA's OSIRIS-REx mission are revealing fascinating secrets about the asteroid's history and potentially the origins of life. Launched in 2016, the mission collected samples from Bennu, located hundreds of millions of kilometers from Earth. In 2020, the spacecraft touched down on the asteroid's surface to collect rocks and dust, gathering 120 grams of extraterrestrial material, which was returned to Earth in 2023.
Initial analysis of the samples reveals an unexpected composition. Salts, including carbonates, sulfates, and fluorides, indicate the presence of salty water on Bennu billions of years ago, long before the asteroid became dry. While the surface is now arid, these salts testify to the existence of water that once flowed through its depths.
Researchers have also discovered organic molecules essential to life, such as 14 of the 20 amino acids needed for protein formation, as well as 5 nucleobases, the building blocks of DNA. This discovery suggests that the basic materials of life could exist elsewhere in the solar system.
However, the amino acids present on Bennu are different from those found on Earth: some are oriented both left and right, unlike those on Earth, which are all left-oriented. This reveals an extraterrestrial chemistry, different from that of our planet.
These discoveries raise the question of whether life could have formed on asteroids. While no form of life has been detected in the samples, the presence of these building blocks of life opens the door to new hypotheses about the origin of life and its possible existence elsewhere in the universe.