Scientists Reveal Rapid Surface Changes on Bennu Driven by Solar Heating
An international team of planetary scientists, guided by researchers from the Cote d’Azur Observatory and working with the OSIRIS-REx mission, has examined the fine cracks on the asteroid Bennu. Their findings show that Bennu’s surface features shift and reshape with surprising speed under the influence of the Sun. The study appears in a reputable science journal, underscoring the dynamic nature of small bodies in our solar system.
Asteroids are among the oldest objects in the solar system, yet they experience constant activity. Collisions and the relentless energy from sunlight continually wear and rearrange their surfaces. Bennu, in particular, shows clear signs of rapid erosion caused by solar heating, which can cause fragments to be ejected into space over time. This observation highlights the delicate balance between ancient material and ongoing surface modification on small bodies.
In addition to the general erosion pattern, the researchers identified temperature-driven expansion and contraction as a key mechanism behind the cracking. By measuring crack lengths and the angles they form, the team detected consistent changes aligned with daily solar heating cycles. The orientation of the cracks, predominantly northwest to southeast, reinforces the idea that temperature fluctuations drive the topography rather than random forces such as landslides. If the cracks were the result of landslides, a more random distribution would be expected. The pattern of alignment thus serves as a meaningful indicator of thermal stress in Bennu’s regolith.
These observations give the surface of Bennu a youthful appearance in terms of its current terrain, even though the underlying rocks are ancient. The upper layers have been stripped away by erosion, exposing older material beneath. The implications extend beyond Bennu itself, offering a window into how small bodies in near-Earth space respond to solar radiation, thermal stress, and micrometeorite impacts. The findings contribute to a growing understanding of how space rocks evolve on timescales that are accessible to human observation and mission data. As part of the OSIRIS-REx mission, scientists anticipate collecting a surface sample from Bennu to further investigate its composition and history in the near future. The mission team outlines a careful plan to retrieve material that can illuminate the timeline of surface processes on asteroids like Bennu. This forthcoming sample return is anticipated to provide crucial clues about the aging process of small bodies and the role of thermal metamorphism in shaping their surfaces.
Ultimately, the work on Bennu emphasizes a broader narrative: asteroids, once thought to be static relics, are active laboratories. The daily sun exposure drives cycles of cracking, stress, and erosion that continually reshape their landscapes. By linking crack orientation to temperature changes, scientists create a robust proxy for assessing the thermal history of these objects. The research team notes that ongoing observations, along with sample analysis from future missions, will refine models of how asteroid surfaces weather over time. The Bennu study thus stands as a testament to how modern space missions blend high-precision measurements with long-standing geological questions to reveal the living history of the solar system.