NASA expects ‘treasure trove’ of data after water found on Bennu

11 Dec 2018

This mosaic image of the asteroid Bennu is composed of 12 Polycam images collected by the OSIRIS-REx spacecraft from a range of 24km. Image: NASA/Goddard/University of Arizona

NASA’s OSIRIS-REx spacecraft has already managed to find water beneath the surface of Bennu, helping to explain more about our solar system.

It was just under a week ago that the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) announced its arrival less than 20km away from the asteroid Bennu.

It will now spend the next year pointing three of its scientific instruments at the chunk of space debris – no bigger in size than a large car – in the hope of finding out more about its composition, as well as choosing a suitable landing site to eventually return 60g of material back to Earth.

Now, despite the mission only being a few days old, NASA has announced that data from two of the spacecraft’s spectrometers – the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES) – have discovered water locked inside the clays of Bennu.

Analysis detected the presence of oxygen and hydrogen atoms bonded together, known as hydroxyls, which the NASA team suspects exist across the entire asteroid in water-bearing clay minerals. This means that at some point, Bennu’s rocky material interacted with water.

While Bennu itself is too small to have ever hosted liquid water, the finding does indicate that liquid water was present at some time on Bennu’s parent body, a much larger asteroid.

‘A treasure trove of new information’

“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,” said Amy Simon, OVIRS deputy instrument scientist.

“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.”

OSIRIS-REx’s cameras helped confirm NASA’s original model of Bennu’s shape – however, the one outlier was the size of the large boulder near Bennu’s south pole. While originally it was calculated to be at least 10 metres in height, preliminary data from the spacecraft’s cameras suggest it is actually closer to 50 metres in height with a width of around 55 metres.

Before OSIRIS-REx gets any closer to Bennu, the spacecraft will remain in orbit until February 2019, with expectations it will get as close as 1.4km from its surface during the first orbital phase. This will set a new record for the smallest body ever orbited by a spacecraft and the closest orbit of a planetary body by any spacecraft.

Colm Gorey was a senior journalist with Silicon Republic