The University of Arizona Press

July 17, 2024

Bennu 3-D, Anatomy of an Asteroid, the world’s first complete (and stereoscopic) atlas of an asteroid, is the result of a unique collaboration between OSIRIS-REx mission leader Dante Lauretta and Brian May’s London Stereoscopic Company. Lauretta’s colleagues include Carina Bennett, Kenneth Coles, and Cat Wolner, as well as Brian May and Claudia Manzoni, who became part of the ultimately successful effort to find a safe landing site for sampling. The text details the data collected by the mission so far, and the stereo images have been meticulously created by Manzoni and May from original images collected by the OSIRIS-REx cameras. The book includes a stereoscopic viewer.

Why did your team choose Bennu as the destination for the OSIRIS-REx spacecraft?

Data from telescopes suggested that Bennu would be a “primitive” asteroid that preserves organic molecules (the building blocks of life as we know it) and water-bearing minerals from early in solar system history. This time-capsule aspect made it a high-value scientific target with the potential to shed light on how our planet and the life on it originated.

There was also a practical consideration in the selection of Bennu—it is a (relatively) nearby asteroid with an orbit that brings it close to Earth every few years. This makes it much more feasible to send a spacecraft there and back than if we were to go to an asteroid in the main belt. 

How many cameras were on OSIRIS-REx and what were their different purposes?

The spacecraft has two camera suites, each with three cameras, for six cameras total.

The OSIRIS-REx Camera Suite (OCAMS) (built by U of A) imaged the asteroid at global to local scales, providing data to construct the maps and digital terrain models needed for effective and safe sampling. OCAMS includes:

• PolyCam, a telescopic camera with a zoom lens, which first detected Bennu from more than two million kilometers (1.24 million miles) away and later imaged the sample site in millimeter-scale detail;
• MapCam, a multispectral imager that used color filters to map the diversity of materials on Bennu’s surface;
• SamCam, a close-range camera used to photo-document the sample collection event.

The Touch and Go Camera System (TAGCAMS) (built by Malin Space Systems) is an engineering camera suite designed to support navigation and operations. It also ended up serendipitously supporting science by capturing images of rock particles ejecting from Bennu. TAGCAMS includes:

• NavCams 1 and 2, two identical imagers that photographed Bennu and the background starfield for navigation purposes.
• StowCam, which photo-documented the stowage of the sample in the capsule for delivery to Earth.

What did you learn about Bennu that you didn’t expect?

Lots! A primary theme of the mission was the curveballs that Bennu threw at us. Probably the biggest surprise was that we expected Bennu to be covered in sandy material, like a beach, that would be relatively easy to sample. In fact, it turned out to be covered in boulders, some the size of buildings, which was scientifically fascinating but made sampling a real challenge.

Another surprise was the serendipitous discovery, in navigation images, of tiny shards of rocks ejecting from Bennu’s surface, apparently spontaneously. This phenomenon was observed many times over the course of the mission. The science team concluded that it is probably caused by rocks breaking when meteoroids strike them and/or cracking under the strain of Bennu’s dramatic temperature changes.

A third surprise was the discovery of large (meter-scale) veins of carbonate minerals in some boulders. (An example of carbonate minerals on Earth is the white crust that forms around sinks and water fixtures.) Such large veins mean that back when Bennu was part of a larger asteroid, there was water flowing extensively under the surface, depositing the veins.

Finally, we were surprised to find that when our sampling device made contact with the surface, it sunk into Bennu as though into a plastic ball pit, rather than coming to rest on firm ground. This means that Bennu’s surface is made of particles that are very loosely packed and barely held together by any cohesion at all. If we had not fired the thrusters to back away, the spacecraft might have been swallowed by the asteroid as a result.

How did you happen work with Brian May and the London Stereoscopic Company to create Bennu 3-D, Anatomy of an Asteroid?

Brian and Dante first began corresponding as early co-supporters of the global Asteroid Day campaign. This correspondence eventually grew into Brian and his colleague Claudia Manzoni becoming active members of the OSIRIS-REx science team. They created numerous stereo (3-D) images from the spacecraft camera imagery that, in addition to being stunning to look at, were instrumental in helping the team understand Bennu’s rugged terrain and identify a safe sampling site. So it made perfect sense to work with them when it came time to create this atlas of Bennu.

What are the next steps for the OSIRIS-REx mission?

We are all looking forward to the delivery of the sample from Bennu to Earth on September 24, 2023. That event will kick off two years of intense laboratory analyses all over the world to test hypotheses about Bennu’s origin and evolution.

After the spacecraft drops off the sample, it will continue on its orbit in preparation for a second mission, called OSIRIS-APEX, that will rendezvous with the asteroid Apophis in 2029. Observing another asteroid with the same state-of-the-art cameras and instruments will offer exciting opportunities for comparison.