Riding Along on a Historic Asteroid Mission

On Sept. 24, 2023, a space capsule about the size of a used tire landed in a patch of Utah desert not far from Salt Lake City. Aboard was a tiny chunk of an alien world — roughly half a pound of rocks from an asteroid called Bennu. 

This “sample return” was the culmination of one phase of a NASA mission called OSIRIS-REx. The OSIRIS-REx spacecraft launched in 2016, beginning a seven-year journey to study and even pick up a piece of Bennu — which is about as tall as the Empire State Building and shaped a bit like a spinning top. 

Researchers at CU Boulder were along for the ride. Daniel Scheeres, distinguished professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences, led a team that used the spacecraft’s navigational instruments to peer deep inside the asteroid. The group’s research data is opening a new window into the dawn of the solar system billions of years ago.   

Among other things, the researchers — which included four graduate students — discovered that Bennu’s interior may be much less dense than its outer layers — like a créme-filled chocolate egg in space. 

As for the sample of Bennu, Paul Sánchez, senior research associate of aerospace engineering, will help analyze that treasure. He’ll explore how tiny grains of rocky material can hold themselves together to form a massive space behemoth like Bennu. 

“We were hoping to find out what happened to this asteroid over time, which can give us better insight into how all of these small asteroids are changing over millions, hundreds of millions or even billions of years,” Scheeres said. “Our findings exceeded our expectations.”