By 
June 9th, 2020
NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft.
Credit: NASA/Goddard/University of Arizona
NASA’s OSIRIS-REx spacecraft has been making close-up observations of asteroid Bennu. Those images contain the first evidence of thermal fracturing of rocks on an airless body.
Thermal fracturing or thermal stress weathering occurs as rocks heat and cool each day, and mechanical stresses build up that can cause cracks to develop and grow. Over time the cracks grow larger and cause the rock to disaggregate or split into multiple pieces.
Planetary Science Institute (PSI) research scientist Jamie Molaro explains: “This is the first time evidence for thermal fracturing has been definitively observed on an object without an atmosphere.”
NASA’s OSIRIS-REx Finds Heat, Cold Fracturing Rocks on Asteroid Bennu
Examples of disaggregation (top) and linear fractures (bottom) in boulders of varying sizes on Bennu.
Credit: NASA/Goddard/University of Arizona
The research findings have been published in a Nature Communications paper.
Piece of a puzzle
“Like any weathering process, thermal fracturing can cause the evolution of boulders and planetary surfaces over time; from changing the shape and size of individual boulders, to producing pebbles or fine-grained regolith, to breaking down crater walls,” Molaro said in a PSI statement.
“How quickly this occurs relative to other weathering processes tells us how quickly the surface has changed. It is one piece of a puzzle that tells us what the planetary surface used to be like, and what it will be like millions of years from now,” Molaro explains. “We don’t have good constraints yet on breakdown rates from thermal fracturing, but we can get them now that we can actually observe evidence for it for the first time in-situ.”
The Planetary Science Institute is headquartered in Tucson, Arizona.
PSI’s Molaro is lead author of the paper “In situ evidence of thermally induced rock breakdown widespread on Bennu’s surface” published June 9, 2020 and can be found at:
Posted in Space News
