Cosmochemist Wang to study samples from asteroid Bennu

Kun Wang, assistant professor of Earth and planetary sciences and faculty fellow in the McDonnell Center for the Space Sciences, was selected for NASA’s OSIRIS-REx Sample Analysis Participating Scientist Program. OSIRIS-REx is the first NASA mission to visit a near-Earth asteroid and will return a sample to Earth in 2023. As part of the program, Wang received a three-year $503,856 grant to investigate moderately volatile element isotopic compositions of asteroid Bennu as well as their implications for the asteroid’s volatile depletion history.


Reaching far-off asteroids – much less returning material from them – is incredibly challenging. But, according to Wang, the payoff of sample return missions is well worth the effort. By collecting pristine samples directly from asteroid Bennu, planetary scientists have the opportunity to glean information about the early solar system that’s unavailable in meteorites found on Earth.

“The samples returned by the OSIRIS-REx mission from asteroid Bennu are expected to represent the oldest and most primitive materials of the solar system available to us,” Wang said.

Unlike planet Earth, which has undergone planetary consolidation and other major upheavals since the birth of the solar system, asteroid Bennu comprises relatively pristine materials from the primitive solar system. These materials likely originated from the outer solar system, beyond the snow line, where the temperature remains cold to preserve ice, volatiles, and organics. In addition, samples collected from Bennu are also free from terrestrial contamination and weathering, and they haven’t suffered the extreme heating events meteorites face when entering Earth’s atmosphere.

“Based on remote sensing of Bennu, we think the samples are compositionally similar to CI chondrites, which we can very rarely collect as meteorites on Earth,” Wang said. “CI chondrites are very fragile and don’t preserve well as meteorites reaching Earth via atmospheric entry. That is probably why there are only five CI chondrite falls having been observed so far among more than 70,000 meteorites in total. By collecting these extremely rare and valuable materials directly from an asteroid, Bennu, we may identify organics and volatiles that represent the most pristine samples of the Sun and bulk solar system.”

Wang will examine water and other volatiles in the returned samples to map the volatile history of the solar system, an important step in understanding the evolution of our planetary neighborhood.