Samples of rocks and dust from the asteroid Bennu, located near Earth, contain organic matter, including amino acids and all five nucleobases of DNA and RNA, as well as salts formed early in its history. These findings offer new insights into the chemistry of the early solar system.

The findings offer new insights into the chemistry of the early solar system. These findings are presented in two studies published in the journals Nature Astronomy and Nature.

In 2018 the OSIRIS-Rex mission reached the near-Earth asteroid Bennu to collect samples. This asteroid has long piqued the interest of researchers because of its near-Earth orbit and carbon-rich composition. By analysing these samples, which are the first asteroid surface samples NASA has received in space and the only ones collected from a planetary body in almost 50 years since the Apollo missions, researchers have found thousands of organic molecular compounds. These compounds included 14 of the 20 protein amino acids present in Earth’s life forms, 19 non-protein amino acids that are rare or absent in biology, and all five biological nucleobases (adenine, cytosine, guanine, thymine and uracil).

The asteroid was also found to be rich in nitrogen- and ammonia-containing compounds that formed billions of years ago in cold, distant regions of our solar system. The researchers note in their study, published in Nature Astronomy, that Bennu has a much richer organic matter complexity than Earth’s biology and suggest that the body from which the asteroid originated may have been in the outer solar system.

In the second Nature paper, the researchers analysed the samples and found a variety of saline minerals, including sodium-containing phosphate salts and sodium-rich carbonates, sulphate salts, chloride salts and fluoride salts.

These salts may have formed during the evaporation of the salty liquid present early in the history of the body from which Bennu came, indicating that water was once present. The possible presence of water along with the nucleobases raises questions about the process that creates the building blocks for life (probiotic synthesis of organic molecules), which will require further research.