OSIRIS REX discovers water on asteroid Bennu

Water has been spotted across the surface of asteroid Bennu by NASA's OSIRIS REx spacecraft. The probe will spend years investigating the space rock, returning a sample to Earth in 2023.

OSIRIS REX entered orbit around Bennu on 3 December 2018, and is now around 19km above the surface. Image Credit: NASA/Goddard/University of Arizona
Published: December 11, 2018 at 12:00 pm
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OSIRIS REX , NASA’s asteroid-investigating spacecraft, has found water on the asteroid Bennu. The announcement, made on 10 December 2018, comes just a week after the spacecraft arrived at Bennu.


However, the discovery was made during the spacecraft’s approach to Bennu between August and December.

During this time, OSIRIS REX studied the asteroid with its Visible and Infrared Spectrometer (OVIRS) and Thermal Emission Spectrometer (OTES).

These spotted molecules containing oxygen and hydrogen, known as hydroxyls, across the surface of the asteroid.

These could be signs Bennu interacted with water at some point in its past, and that the parent body it was once a part of might have possessed liquid water.

"It is very exciting to see these hydrated minerals distributed across Bennu's surface, because it suggests they are an intrinsic part of Bennu's composition, not just sprinkled on its surface by an impactor," says Ellen Howell, from the University of Arizona and a member of the mission's spectral analysis group.

Asteroid Bennu is a remnant from early in the formation of the Solar System, and OSIRIS REX will spend several years studying the asteroid in detail to give planetary geologists a better insight into the conditions which the planets formed in.

Not all this observation will be remote, however, as the mission plans to take a sample of the asteroid.


“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,” says Amy Simon, from NASA’s Goddard Space Flight Center and a deputy instrument scientist for OVIRS.


Ezzy Pearson is the News Editor of BBC Sky at Night Magazine. Her first book about the history of robotic planetary landers is out now from The History Press.

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