OSIRIS-REx Discovers Water on Asteroid Bennu

Only a week after reaching the asteroid, NASA's newest spacecraft is already making scientific discoveries.

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NASA/Goddard/University of Arizona

NASA’s OSIRIS-REx spacecraft has been in orbit around the near-Earth asteroid Bennu for about a week now, and it’s not wasting any time. On Monday, NASA that OSIRIS-REx had found water on the surface of the asteroid.

During OSIRIS-REx’s two year-long approach to Bennu, the spacecraft took a lot of pictures. Most of those showed the asteroid as a tiny dot against the backdrop of space. But in recent months, the pictures have started to show features. In addition, the asteroid finally moved into range of OSIRIS-REx’s spectrometers, which are instruments designed to measure what the asteroid is made of.

When OSIRIS-REx aimed those spectrometers at Bennu, they spotted signs of hydrogen and oxygen molecules bonded together in groups called hydroxyls. These hydroxyls are all over the asteroid in various rocks and clays, and the most likely way they could have gotten there is through some sort of interaction with water.

That doesn’t mean water is still present on Bennu. The asteroid is too small to actually hold any liquid water, and if it ever did have water, that would likely have been when it was part of a much larger parent asteroid.

Now that OSIRIS-REx has arrived and is orbiting Bennu, NASA scientists have the ability to study the asteroid at their leisure. Over the next year or two, we’ll likely get a much clearer picture of Bennu’s history.

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