NASA OSIRIS-REx Finds Water On Bennu Asteroid Within Days Of Arrival

On December 3, NASA announced that its OSIRIS-REx spacecraft had successfully arrived as the asteroid called Bennu, kicking off a mission that will last two years. The spacecraft has only been at the asteroid for a week, but its observations already include a big discovery: the presence of water on the space rock.

NASA announced the new discovery in a statement today, saying the water is "locked inside" of the clays on Bennu. Using OSIRIS-REx's Visible and Infrared Spectrometer tool, as well as its Thermal Emission Spectrometer, the spacecraft discovered the presence of hydroxyls — that is, molecules that contains oxygen and hydrogen atoms.

NASA researches believe the hydroxyl groups are likely found within other clay minerals across the asteroid, which would mean that the space rock had "interacted with water" at some point in the past. Bennu is too small to have been the host of the water on its own, the space agency explains, which points toward its bigger parent body as the likely source.

NASA's OVIRS deputy instrument scientist Amy Simon explained the significance of this discovery, saying:

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. When samples of this material are returned by the mission to Earth in 2023, scientists will receive a treasure trove of new information about the history and evolution of our solar system.

As well, NASA says that observations made by OSIRIS-REx have confirmed that a 2013 model of the asteroid "closely predicted" its actual shape, rotation rate, diameter, and other aspects. There is one notable outlier, however: a boulder near the asteroid's south pole, which was expected to be around 33ft in height, but is actually around 164ft.