OSIRIS-REx space probe catches a whiff of water on asteroid Bennu

But how Earth ended up with all its water is still a mystery

bennu_asteroid
Image credit: NASA/Goddard/University of Arizona

NASA’s OSIRIS-REx spacecraft has discovered water on the asteroid Bennu less than a week after its arrival at the hunk of space rock.

The journey to Bennu began over two years ago when OSIRIS-Rex left Earth, it has been chugging along since travelling 1.2 billion miles (2 billion kilometers) to get within 12 miles away from the asteroid on 3 December.

Now, data taken from the probe’s spectrometers reveals that hydroxyls, a group of molecules containing an oxygen atom bonded to a hydrogen atom. Alcohol is an example of a hydroxyl group bonded to a carbon compound.

The presence of these molecules hints that Bennu was once in contact with water, and the fluid seeped into its clay minerals. It is believed that the tabletop spinner-shaped rock was part of a larger asteroid that contained liquid water.

“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 at NASA’s Goddard Space Flight Center in Maryland.

“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.”

Bennu, measuring less than 500 meters in diameter, is an ancient remnant leftover from the protoplanetary disk of gas and dust that compressed to form the Solar System over 4.5 billion years ago. Scientists reckon that some parts of the asteroid may contain tiny specks of dust that are even older than the Solar System.

Bennu

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It is a dark asteroid rich in carbon and probably carries complex organic compounds necessary to kickstart the origin of life. Asteroids classified as Near Earth Objects (NEOs) like Bennu have slammed into Earth many times, leaving behind materials and water.

In a separate project, researchers from the John Hopkins University and the Massachusetts Institute of Technology estimated that about 53 current NEOs over a kilometer in size carry water. Their data published in a paper on arXiv suggests that “hydrated NEOs are unlikely to bring enough water to account for the ice found at the lunar poles, though it is possible that asteroid-delivered hydrated minerals could be found near their impact sites across the lunar surface.”

The OSIRIS-Rex spacecraft will continue inching closer to Bennu, eventually entering its orbit on 31 December. It’ll remain there until February next year, reaching somewhere between 1.2 to 0.9 miles from its surface. After that, it is expected to make another deep dive to get 0.6 miles away.

Both maneuvers act as practice for when Bennu will make the ultimate move to extend a a 3.35-meter (11 ft) robotic arm, known as the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), to scrape a sample of the asteroid to return it to Earth by 2023. ®

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