Asteroid samples offer insights into solar system evolution


Alex Meshik, research professor of physics and a faculty fellow in the McDonnell Center for the Space Sciences, won a $690,521 grant from NASA to support improving instrumentation and refining analytical techniques in preparation for high precision isotopic analyses of asteroid samples. Meshik aims to study noble gases in extraterrestrial samples to better understand the evolution of small bodies and the early solar system.

“Noble gases in extraterrestrial samples show significant variations in their abundances and isotopic compositions,” Meshik explained. “The diversities in these isotopes are thought to be inherited from the source materials synthesized in various stellar environments. They also contain a record of many processes occurring in the interior of the parent bodies after the accretion, such as thermal metamorphism and aqueous alteration.”

Studying the variations in noble gas isotopes can also reveal key details about what has happened on an asteroid’s surface. Out in the vacuum of space, asteroids are exposed to energetic particles from the solar wind and galactic cosmic rays, which affect their noble gas isotopes. By tracing the duration and condition of energetic particle irradiation, physicists can learn more about alterations taking place on the surface of the parent body, including changes to organic materials.

This mosaic of Bennu was created using observations made by NASA’s OSIRIS-REx spacecraft that was in close proximity to the asteroid for over two years. (Credit: NASA/Goddard/University of Arizona)

Meshik’s noble gas lab was selected by the Japan Aerospace Exploration Agency (JAXA) for initial analyses of samples from asteroid Ryugu. In collaboration with noble gas labs in the UK, France, Switzerland, and Japan, Meshik and his team have already analyzed microgram-size samples returned by the Hayabusa2 mission. Their initial results provide tantalizing details about Ryugu’s composition. With the additional support from NASA, Meshik’s lab will be ready to undertake precise analyses of samples from asteroid Bennu, which are expected to be delivered in September 2023.

“The close relation of Ryugu to the rarest type of chondrites – chemically primitive CI chondrites that are least fractionated from the solar composition – suggests that Earth’s atmosphere works as an effective filter for the influx of fragile meteorites, resulting in a biased sampling of meteorites,” Meshik said. “Comparison of Ryugu samples with the samples from Bennu will constrain the dynamical and chemical evolution of small bodies and the early solar system.”