Among several possible origins for the asteroid Bennu, which recently became the first asteroid ever sampled by a NASA mission, is one very surprising indication: it could have come from a water world. It was an intriguing development that emerged after scientists analyzed the mix of rocks and dust from Bennu, popularly referred to as ‘regolith,’ that was scooped up by NASA’s OSIRIS-REx mission in 2020.
The OSIRIS-REx spacecraft was supposed to travel to Bennu, gather the sample, and return it to Earth for study. The spacecraft succeeded in extracting a sample and sending it 200 million miles back to Earth. Scientists hope that the 4.3-ounce sample may help unlock secrets about the solar system’s past and the type of prebiotic chemistry that could explain how life got its start on Earth.
Preliminary Examination and Discoveries
A preliminary examination study of the sample, published in Meteoritics & Planetary Science, documents compounds that are the elements for biochemistry that makeup known life on Earth today. OSIRIS-REx Sample Analysis Team observed that Bennu contained the building blocks of fundamentals needed in life. Indeed, the regolith is rich in carbon and nitrogen with organic compounds, elements critical to life as we know it. This composition conveys when our solar system was more than 4.5 billion years old. Incredibly, more precious rocks have remained pristine; neither have they melted nor resolidified in the last many billions of years, thereby confirming they are truly ancient.
The Surprise of Magnesium-Sodium Phosphate
The sample also hosts magnesium-sodium phosphate, a piece of asteroidal material that eluded detection in the remote sensing data acquired by the spacecraft at Bennu, whose presence in the sample foreshadows that the asteroid may have broken up from an ancient, small, primitive ocean world. “The presence and state of phosphates, along with other elements and compounds on Bennu, suggest a watery past for the asteroid,” said Dante Lauretta of the University of Arizona, Tucson, co-lead author of the paper and principal investigator for OSIRIS-REx. “Bennu potentially could have once been part of a wetter world. However, this hypothesis requires further investigation.”
Ocean Worlds Connections
The idea that Bennu could have come from a water world is supported by other discoveries involving other celestial bodies. For instance, researchers working on the James Webb Space Telescope recently announced their finding of what they think is an ocean world dubbed K2-18b. K2-18b lies 120 light-years off Earth in the constellation Leo and orbits the habitable zone of a red dwarf star known as K2-18. The planet is thought to be 8.6 times the size of Earth and rich in methane and carbon dioxide, while ammonia is scarce, thus pointing toward a water ocean existing beneath a hydrogen-rich atmosphere.
The Importance of Bennu’s Origins
That Bennu has a watery origin is important for several reasons. It can provide direct proof that water-rich bodies were part of the early solar system and played an important role in the delivery, throughout the system, of volatiles and organics. Some of these efforts have strong implications for the origin of water on Earth and if life could have occurred elsewhere within the solar system. In addition, the organic compounds and water-related minerals on Bennu add to a growing body of data implicating asteroids and comets in delivering raw materials for life to Earth.
Future Investigations
While the assumption that Bennu is derived from a water world is rather compelling, it is not quite convincing and calls for deeper scrutiny. The confirmation of the existence of minerals related to water and what explanation of the process through which Bennu formed will be focused on in future research. Detailed investigations of the returned sample concerning other data missions and telescopic observations of other similar asteroids will also be carried out.
The OSIRIS-REx mission has allowed an understanding of so much about Bennu’s composition and origin, hence putting up the cases for asteroids as a water world. This is but a step toward solving the mystery of our solar system’s systematic history and reminds one of the need for an active search for bodies in space research. The more that scientists learn about Bennu, the more secrets it might give up about the building blocks of life and dynamic processes that shaped our solar system.
