NASA’s OSIRIS-REx mission revealed surprises about the asteroid Bennu. Instead of the expected smooth patches, the spacecraft discovered a rough, boulder-filled landscape. “We expected some boulders, but we anticipated at least some large regions with smoother regolith that would be easy to collect,” said Andrew Ryan from the University of Arizona. Instead, Bennu was almost entirely covered in large rocks.
Interestingly, this was a departure from earlier data collected by NASA’s Spitzer Space Telescope in 2007, which indicated a surface that heats and cools quickly. This finding was contradictory since large boulders should have retained heat longer. It led scientists to wonder: why the difference?
Data from OSIRIS-REx suggested that the boulders might be more porous than initially thought. After bringing samples back to Earth, researchers conducted in-depth studies. They found that the boulders, indeed, are porous, but many also contain a complex network of cracks. These cracks may explain why the asteroid’s surface cools more quickly than expected.
To investigate further, a team at Nagoya University used a technique called lock-in thermography. This method allows scientists to observe how heat travels through materials, similar to how ripples move through water. “The thermal inertia measured in the lab samples turned out to be much higher than what the spacecraft’s instruments had recorded,” Ryan pointed out.
At NASA’s Johnson Space Center, researchers carefully handled the delicate samples. Using X-ray computed tomography (XCT), they scanned the samples without exposing them to Earth’s atmosphere. “The sample goes into its own ‘spacesuit,’ gets a CT scan, and then comes back to its pristine environment,” explained Nicole Lunning, a sample curator at NASA. This process created a detailed 3D map of each sample, preserving their structure for future studies.
What emerged from this research was intriguing. The boulders on Bennu were not just porous; they were structurally complex with many cracks. “That was the missing piece of the puzzle,” Ryan said.
Ron Ballouz, a co-author of the study, emphasized the significance. This research transforms how scientists interpret asteroids based on thermal data obtained from Earth. “We can finally ground our understanding of telescope observations of the thermal properties of an asteroid through analyzing these samples,” he noted.
This work opens new avenues for asteroid research. As we learn more about Bennu, we also learn about the formation and evolution of our solar system. Understanding these rocks may help us understand more about the resources they could potentially provide in the future.
For a deeper dive, check out the study published in Nature Communications and learn how this knowledge shapes our perspective on asteroids today.
