Samples from the asteroid have revealed a substance typically found in saline lakes on Earth for the first time.

Bennu is a near-Earth asteroid belonging to the carbonaceous asteroid group, with a diameter of approximately 560 meters. From 2018 to 2021, it was studied by NASA's OSIRIS-REx spacecraft. The probe collected samples from the asteroid's surface and brought them back to Earth, releasing a capsule with the samples that landed in the U.S. state of Utah. In total, OSIRIS-REx gathered just over 120 grams of material—twice the amount originally planned by the specialists.

Preliminary analysis of the asteroid samples revealed that it is part of a celestial body with an ocean, formed about 4.5 billion years ago. Scientists are still uncertain about the exact nature of this parent body.

During the initial analyses of Bennu's material, researchers found water within clay minerals, carbon in both inorganic minerals and as organic molecules, as well as magnesium-sodium phosphate (MgNaPO4). The researchers suggested that carbonaceous asteroids similar to Bennu delivered essential life elements to early Earth.

NASA shared part of the samples with several scientific institutions to expedite the analysis process. Among the "chosen ones" were cosmo-geologists from the National Museum of Natural History (USA) and the Natural History Museum (UK). Two teams of scientists collaborated to study the material and published their findings in the journal Nature.

Using a scanning electron microscope, cosmo-geologists examined asteroid material smaller than a micron—less than one-hundredth the diameter of a human hair. They discovered a solution of salts that remained after the evaporation of salty, sodium-rich waters over 4.5 billion years ago, during the formation of the Solar System.

In particular, the researchers found minerals in the solution in the form of solid particles, which formed during the evaporation of water. In total, they contained 11 chemical compounds, including sodium carbonate (Na2Co3)—an inorganic compound also known as soda ash. This compound had never been observed in extraterrestrial material before. On our planet, minerals containing sodium carbonate are typically found in sedimentary rocks, evaporation sites of mineral waters, and salty lakes such as Searles Lake in the Mojave Desert, USA.

It is noteworthy that, according to some hypotheses, salt (primarily sodium chloride, NaCl) played a significant role in the emergence of life on Earth. The primordial oceans that existed in the early stages of the planet's evolution were salty, and this saline solution created a favorable chemical environment for the formation of the first organic molecules and protocells.

"The watery world that Bennu was part of once contained a lot of liquid water. When the water evaporated, brine remained—a solution of salts. Likely, salts and minerals mixed and combined in it, forming more complex structures necessary for life," explained Tim McCoy (Tim McCoy), one of the study's authors.

The authors of the scientific paper are still uncertain whether the conditions on Bennu's parent body could have facilitated the formation of complex organic substances. Further studies of the asteroid material are required.

The ancient brine from Bennu differs from terrestrial analogs: in addition to sodium carbonate, it contains many minerals with phosphorus (P), which is often found in meteorite materials but rarely in compounds from salty lakes. At the same time, there is little boron (B), which is typical for Earth's salty lakes.

The discovery of sodium carbonate minerals in the asteroid samples surprised scientists. Researchers believe that similar brines with Na2Co3 may exist on other celestial bodies, including the dwarf planet Ceres and Saturn's moon Enceladus. Previously, astronomers had found sodium-containing compounds on these objects. The authors of the scientific paper plan to examine all available meteorite samples in museum collections to search for traces of salts. It is possible that they have gone unnoticed in these materials.

Alongside the scientific work of American and British cosmo-geologists, an article was published in the journal Nature Astronomy, where scientists from Japan presented the results of another study of Bennu's samples.

The specialists reported that they discovered numerous amino acids—molecules that form the basis of proteins necessary for life—in the asteroid material. Additionally, all five known nitrogenous bases—organic compounds that are components of nucleic acids—were found.

Nitrogenous bases play a crucial role in creating genetic material. In other words, they are the "building blocks" of RNA and DNA. It is particularly interesting that some of these compounds had never been found in meteorite materials before. According to the authors of the scientific paper, their findings support the hypothesis that carbonaceous asteroids may have brought the "building blocks of life" to Earth.

The samples from Bennu, delivered to Earth by the OSIRIS-REx probe, will be studied by scientists for decades. During their research, cosmo-geologists hope to make discoveries that will help unravel the mystery of the emergence of life on Earth.