Cracks explain why Bennu’s rugged boulders lose heat

When OSIRIS-REx reached asteroid Bennu in 2018, the spacecraft found a jagged, boulder-strewn world instead of the smoother, finer regolith many had expected. Andrew Ryan, who led the mission’s sample physical and thermal analysis working group, said the team anticipated some large smooth regions but instead encountered mostly boulders.

That finding conflicted with 2007 measurements from the Spitzer Space Telescope, which showed low thermal inertia indicative of a surface that heats and cools quickly, like a sandy beach. Initial study of the returned samples showed the rocks were porous enough to account for part of the heat loss, but many turned out to be riddled with extensive networks of cracks.

Scientists at Nagoya University applied lock-in thermography to the sample material and found laboratory thermal inertia was much higher than the spacecraft had recorded, mirroring results from Hayabusa-2.

Japan, Nagoya

bennu, osiris-rex, thermal inertia, boulders, regolith, spitzer telescope, cracks, lock-in thermography, hayabusa-2, nagoya university