NASA cracks the mystery of asteroid Bennu: Its giant rocks reveal a surprising feature
The samples collected reveal that the rocks are riddled with numerous internal cracks
Asteroid Bennu has puzzled scientists for years. Its surface is covered with massive boulders, a landscape that should, in principle, retain heat for longer. However, observations from space showed that the asteroid heated up and cooled down unexpectedly quickly. Now, researchers have found an explanation by analyzing samples collected by NASA.
The study, published in Nature Communications, found that Bennu’s rocks contain extensive networks of internal fractures. These cracks, combined with the material’s high porosity, help explain its unusual thermal behavior and solve a mystery that had puzzled researchers for years.
The hidden cracks changing what we know about Bennu
OSIRIS-REx arrived at Bennu in 2018 and encountered a surface far more rugged than expected. Scientists had anticipated large areas covered with fine material, but instead found terrain dominated by large boulders. The mystery deepened when that landscape was compared with previous thermal measurements showing that the asteroid lost heat rapidly.
To investigate the phenomenon, researchers analyzed rock fragments brought back to Earth and used X-ray computed tomography (XCT). The technology allowed them to examine the samples’ internal structure in three dimensions without damaging them. The researchers then used the data in computer simulations to study how heat moves through larger rocks.
The results showed that porosity alone was not enough to explain the phenomenon. The internal fractures were a crucial piece of the puzzle. “They’re really cracked up, and that was the missing piece,” explained Andrew Ryan, a researcher at the University of Arizona who led the team responsible for analyzing the samples’ physical and thermal properties.
The discovery could also help scientists better interpret observations of other asteroids. Until now, researchers have faced challenges connecting thermal measurements made from space with the actual physical properties of asteroid rocks. Directly analyzing extraterrestrial material provides a way to connect the two types of data and improve our understanding of these celestial bodies.
