Asteroid Bennu holds secrets of water evaporated billions of years ago, study shocks

Yahoo

30-01-2025

The answer to the origins of life on Earth may lie scattered across the solar system. That's why NASA launched a mission to the near-Earth asteroid Bennu in 2016.
In 2020, the OSIRIS-REx mission made history by successfully collecting a sample from the asteroid. This was the first U.S. asteroid sample return, a feat not achieved in nearly 50 years since the Apollo missions.
And in September 2023, that precious cargo returned. The space community eagerly awaited the chance to analyze these samples, hoping to unlock the secrets of Bennu and, perhaps, the beginnings of life.
Now, the examination of these samples has provided new insights about life on Earth.
Scientists have discovered a unique sequence of minerals that formed from evaporated water in samples from Bennu. These minerals date back to the early solar system and include compounds never before seen in extraterrestrial samples.
Researchers from the Smithsonian's National Museum of Natural History conducted this study.
'We now know from Bennu that the raw ingredients of life were combining in really interesting and complex ways on Bennu's parent body. We have discovered that next step on a pathway to life,' said Tim McCoy, the museum's curator of meteorites and the co-lead author.
Bennu's parent body formed 4.5 billion years ago and once contained pockets of liquid water. As the water evaporated, brines similar to Earth's salt flats remained.
Bennu's near-Earth orbit and carbon-rich makeup have made it a target of scientific interest. It has been theorized that this asteroid contained water and organic molecules. Bennu and other similar asteroids may have been responsible for delivering these life-building materials to early Earth.
For these reasons, NASA sent a mission to collect samples from this asteroid.
Some of its samples were 'loaned' to researchers globally, including to the team at the Natural History Museum.
Researchers used a powerful scanning electron microscope to examine extremely tiny features (less than a micrometer, or 1/100th the width of a human hair) on fragments of the Bennu asteroid.
This brine contains compounds never before seen in other extraterrestrial samples, including water-bearing sodium carbonate compounds, commonly known as soda ash.
Sodium carbonates are found naturally on Earth in evaporated lakes rich in sodium, like Searles Lake in the Mojave Desert.
The unexpected discovery of sodium carbonate in the Bennu samples led researchers to investigate further.
McCoy examined similar minerals in the museum's collection and consulted with colleagues studying other Bennu samples. This collaborative effort revealed a total of 11 minerals that likely formed in a brine environment on Bennu's parent asteroid.
The mineral makeup of Bennu's brine is distinct from Earth's.
Bennu's brines contain interesting minerals and elements, but it's unknown if they could form complex organic molecules.
It's still unclear whether this environment was truly capable of creating life itself, but the discovery of these brines is a significant step forward. It suggests that similar conditions might exist on other celestial bodies, like the dwarf planet Ceres or Saturn's moon Enceladus. Interestingly, sodium carbonate has been detected on Ceres and Enceladus.
'We now know we have the basic building blocks to move along this pathway towards life, but we don't know how far along that pathway this environment could allow things to progress,' McCoy said in the press release.
The findings were published in the journal Nature.