Long before it sounded alone, a small, distant asteroid called Bennu had a wet and watery start, according to fresh evidence recently announced by NASA.
NASA's OSIRIS-REx probe, which arrived in Bennu on December 3 after a two-year journey, is currently positioned about 20 kilometers above the surface of the asteroid. He recently returned data indicating that the asteroid's surface is filled with clay-like minerals that indicate that parts of that rock had liquid water at some point in its distant past.
"Bennu seems to be a very rich target in water, and water is the most interesting and perhaps most profitable product you would get from an asteroid," said Dante Lauretta, principal investigator for the OSIRIS-REx mission, at a news conference. today.
Water is considered valuable for future space missions because it is a potential source of fuel. Being able to extract asteroids into the water would mean that future missions would not have to depend on the Earth as fuel, and could potentially exploit the Solar System further.
It is important to note that although Bennu may be rich in water, this does not mean that there is liquid water on its surface now. At just over 1,600 feet in diameter, Bennu is currently so small that its surface is unable to withstand liquid water. Researchers hypothesize that between 800 million and a billion years ago, the boulder-filled boulders we know as Bennu were probably part of a larger asteroid, over 100 kilometers in diameter, which would be large enough to support the water. Planetary scientists think that the larger body was broken in a huge collision, leaving smaller pieces like Bennu floating in space in clumps that resemble huge piles of debris.
People working on the project have long suspected that Bennu could have these kinds of water-rich clays. "Bennu is proving to be just the asteroid we were hoping for," said Jeff Grossman, a scientist for the OSIRIS-REx mission program at today's press conference.
The spacecraft had its first glimpse of its target in August of this year, when Bennu was still distant, 1.4 million kilometers away. In recent months, the surface of the asteroid has come into focus, and researchers now have a much better idea of what is done. During the approach, spacecraft instruments picked up readings showing that there were water-rich clays on the surface of Bennu.
"This is really great news and this is a big surprise," said Amy Simon, deputy instrument scientist for the OSIRIS-REx mission at the press conference.
In addition to the presence of previously wet materials, the researchers also announced that they collected enough data to create a more accurate 3D model of the asteroid's surface.
The model may look solid, but Bennu has hidden depths. Based on the data collected so far, the researchers estimate that up to 40% of the interior of Bennu could be simply empty.
OSIRIS-REX will enter orbit around Bennu on December 31 and eventually begin mapping its surface in detail. The spacecraft will be close to Bennu for the next few years, waiting until 2020, when it will contact the asteroid surface, hopefully by taking a sample before leaving in 2021. It is expected to return – with whatever is collected – back to the Earth in 2023.