In September 2023, NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission became the first U.S. mission to collect a sample of material from an asteroid and return it to Earth.
Now, a team including researchers at Lawrence Livermore National Laboratory (LLNL) has analyzed that material. Their work, published in Nature Astronomy, shows that the elements in the asteroid Bennu reflect the early composition of the solar system.
"We found that Bennu has an elemental composition that very closely matches the sun. That means the material recovered from Bennu is a great reference for the starting composition of the entire solar system," said author and LLNL scientist Greg Brennecka. "It is remarkable that Bennu has survived so long without seeing high temperatures that would 'cook' some of the ingredients."
Scientists are still studying how planets form, and learning the initial composition of the solar system is like obtaining the list of ingredients to bake a cake.
"With that ingredients list, we now have a better idea of how those elements all came together to form the planets in our solar system, and, eventually, Earth and its living inhabitants," said Brennecka. "If we are to learn about our origins, the starting point is the composition of the solar system."
By returning a pristine sample to Earth and avoiding any contamination from our planet, OSIRIS-REx opened up new opportunities.
"The amount of information you can obtain from returned sample material in the laboratory is incredible," said author and LLNL scientist Quinn Shollenberger. "We simply cannot answer the big 'origins' questions without having the sample on Earth."
The team at LLNL was responsible for measuring the bulk elemental and isotopic compositions of the Bennu sample with state-of-the-art precision.
"One of our goals is to determine what elements in the periodic table, and in what proportions, the solar system started with," said author and LLNL scientist Jan Render. "Bennu allows us to find this out."
To obtain these results, the researchers crushed the asteroid material into a fine powder and dissolved it in acid. Then, they fed it into a suite of mass spectrometers at LLNL, which provided the concentrations of most elements in the periodic table. From there, the team has been separating the sample by element, and, so far, they have been able to analyze isotope ratios of several elements.
"One perk of working at a national laboratory is the amazing analytical capabilities that we have at our disposal and experts in utilizing state-of-the-art machinery," said author and LLNL scientist Josh Wimpenny. "Having these capabilities all in one place is very unique, and we get better use out of these precious materials."
LLNL will continue to analyze results from Bennu, which still has a plethora of information to provide. Looking ahead, the Laboratory aims to position itself to analyze lunar samples that will be retrieved as part of the Artemis program.
