Count on the cosmos when it comes to surprises. OSIRIS-REx discovered two fascinating things about Bennu: its terrain and particle plumes.

NASA's Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer or OSIRIS-REx has only one mission in mind: reach Bennu, an asteroid.

Known as the smallest heavenly body studied by a spacecraft, Bennu is only 1,600 feet wide. Its width, therefore, is about the same as the height of the Empire State Building.

Despite its smallness, it may hold the answers to some of the world's longest-standing questions such as the origins of the universe.

NASA believes the asteroid may contain unaltered carbon material. In December 2018, the mission team revealed it contains traces of hydrogen and oxygen molecules. Bennu, however, is an active asteroid.

Ejecting Materials Into Space

Active asteroids are not new, but they are also rare. There are only less than 15 active asteroids that send particles into space. Bennu is one of them.

NASA first detected the plumes on Jan. 6. Since then, there have been 11 of such events.

Because some of them end up right into orbit and even temporary moons, the scientists wanted to find out if they pose some risks for the OSIRIS-REx. The spacecraft is currently in orbit and about to collect samples by 2020. Then, it will deliver the specimen to Earth in 2023.

Using the same tools they use to assess the risks of asteroids and meteorites hitting the Earth's satellites, they discovered the odds for the spacecraft were low.

They also learned that the particles were a combination of dust and other materials. The exact cause for the activity remains unknown. NASA, however, is up to the challenge.

"The first three months of OSIRIS-REx's up-close investigation of Bennu have reminded us what discovery is all about-surprises, quick thinking, and flexibility," said Lori Glaze, NASA's Planetary Science Division acting director.

The More Rugged Terrain

Bennu's particle plumes are only half of the problem. The other is the terrain. The near-Earth asteroid does have a rough surface from almost end to end. Considering the size, the spacecraft was created to aim at a target circle of 82 feet in diameter.

The up-close observations from the spacecraft, though, revealed even more boulders, which are not only tall but also dense.

The discovery led to the scrapping of the previous site and the search for a few candidate spots that are much smaller than 82 feet. It will also require higher precision and performance from OSIRIS-REx.

NASA is presently recalibrating their models and techniques, but it may learn from the Japanese space agency. It encountered the same problem with Hayabusa2 spacecraft when landing on Ryugu.

The science team behind the mission presented these findings and more during the 50th Lunar and Planetary Conference on March 19 in Houston, Texas.