As NASA’s OSIRIS-REx spacecraft completes its two-year, 1.2-billion-mile journey, it now begins its next phase: a survey of the strange asteroid Bennu.

At about 12 p.m. EST on Monday, OSIRIS-REx transitioned from moving toward the asteroid into moving around the asteroid. This shift marks the start of the most crucial portion of the spacecraft’s mission: getting the samples back to Earth. NASA scientists hope they will unlock the mysteries of the solar system’s beginnings — as well as determine whether asteroids like Bennu could be fuel sources for future deep space missions.

OSIRIS-REx will survey Bennu with a series of flyovers, passing as close as four miles to the asteroid’s surface over the next several weeks before settling into orbit on December 31. When the spacecraft does this, Bennu, at just 1,600 feet across, will become the smallest object ever orbited by a spacecraft. OSIRIS-REx will spend over a year in a tight orbit some 0.75 miles from Bennu’s surface. Starting in February, it will begin creating a 3-D map of its surface, plotting the best place to land and snag a sample of regolith.

OSIRIS-REx is expected to bring its samples home by September 2023, and if it succeeds, its cargo will be the largest sample to have returned return to Earth from space since the end of the Apollo program. The contents of that sample are the crux of the whole OSIRIS-REx mission.

OSIRIS-REx nearing Bennu.
OSIRIS-REx nearing Bennu.

Bennu, a primitive B-type asteroid, is rich in organic compounds that scientists suspect have changed very little since the formation of the solar system.

“Bennu as an asteroid, and as a carbonaceous asteroid, we believe is like a time capsule from the beginning of the solar system,” Erin Morton, communications lead for the University of Arizona’s Lunar and Planetary Laboratory told Inverse on Monday. “The makeup of Bennu hasn’t changed. There’s been no weathering. Because of that, we want to go and look and see what carbon looked like at the very beginning.”

Scientists also hope that the carbon-rich compounds on Bennu and other asteroids like it could someday provide fuel for deep space missions. By examining the carbon-rich compounds on Bennu, we could get a better idea of how to best convert these substances into fuel crewed or uncrewed spacecraft on future missions. We’re still a long way from converting Bennu into an interplanetary gas station, but OSIRIS-REx takes us a step in that direction.

“As explorers, we at NASA have never shied away from the most extreme challenges in the solar system in our quest for knowledge,” Lori Glaze, acting director for NASA’s Planetary Science Division, said in a statement on Monday. “Now we’re at it again, working with our partners in the U.S. and Canada to accomplish the Herculean task of bringing back to Earth a piece of the early solar system.”

Photos via NASA, NASA/Goddard/University of Arizona