NASA’s OSIRIS-REx spacecraft found water inside the minor planet Bennu that it landed on last week.

Early data from the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission revealed water locked inside Bennu.

Information gathered by the spacecraft’s OVIRS and OTES spectrometers reveals the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as “hydroxyls.”

Scientists believe these hydroxyl groups exist across the asteroid in water-bearing clay minerals, suggesting that, at some point, Bennu’s rocky surface interacted with water, Geek reported.

The orb itself is too small to have hosted liquid water, according to NASA. But fluids were present at some point on Bennu’s parent body—a much larger asteroid.

“The presence of hydrated minerals across the asteroid confirms that Bennu, a remnant from early in the formation of the Solar System, is an excellent specimen for the OSIRIS-REx mission to study the composition of primitive volatiles and organics,” Amy Simon, OVIRS deputy instrument scientist at NASA’s Goddard Space Flight Center, said in a statement.

“When samples of this material are returned by the mission to Earth in 2023,” she continued, “scientists will receive a treasure trove of new information about the history and evolution of our Solar System.”

More than two years after its launch in September 2016, OSIRIS-REx finally reached the near-Earth asteroid last week. The spacecraft is now in survey mode, flying over Bennu’s north pole, equator, and south pole at close ranges to determine the planetoid’s mass.

“Our initial data show that the team picked the right asteroid as the target of the OSIRIS-REx mission,” Dante Lauretta, principal investigator at the University of Arizona, Tucson, said. “We have not discovered any insurmountable issues at Bennu so far.

“The spacecraft is healthy and the science instruments are working better than required,” he added. “It is time now for our adventure to begin.”

The third New Frontiers planetary science mission (following Juno and New Horizons), OSIRIS-REx is expected to return to Earth with a collected specimen in September 2023.