Scientists from NASA’s OSIRIS-REx found that the sun’s heat destroyed Bennu’s rock in just 10,000 to 100,000 years, suggesting that surface regeneration on asteroids is much faster than on Earth.
For the results, the team analyzed rock cracks in the asteroid Bennu from high-resolution images taken by the OSIRIS-REx (Origin, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) spacecraft.
This information will help scientists estimate how long it will take rock on an asteroid like Bennu to break up into smaller particles that can be ejected into space or remain on the asteroid’s surface.
Tens of thousands of years may sound very slow, but “we think it will take millions of years for the asteroid’s surface to regenerate,” said Marco Delbo, a senior scientist at the University of Côte d’Azur in France.
“We were surprised to learn that the asteroid’s aging and weathering processes were geologically rapid,” Delbo said.
Bennu’s rapid temperature change had created internal stresses that cracked and cracked the rock, like cold glass cracking under hot water.
The sun rises on Bennu every 4.3 hours. At the equator, daytime highs can reach nearly 127 degrees Celsius, and nighttime lows drop to nearly minus 23 degrees Celsius.
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OSIRIS-REx scientists found cracks in rocks in spacecraft images from the first study of the asteroid. The cracks appear to be pointing in the same direction, “a clear indication that temperature shocks between day and night could be to blame,” Delbo said.
Delbo and his colleagues measured the lengths and angles of more than 1,500 faults in the OSIRIS-REx images: some shorter than a tennis racket, others longer than a tennis court.
They found that the fracture was primarily northwest-southeast oriented, suggesting that it was caused by the Sun, which is shown here as the main force changing Bennu’s landscape.
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“If a landslide or impact moves rock faster than rock breaks, the faults will point in random directions,” Delbo said.
The scientists used computer models and their fracture measurements to calculate a 10,000 to 100,000 year time frame for thermal fractures to spread and split rock.
“The Bennu thermal fracture is similar in formation to those we find on Earth and Mars,” said Christophe Matonti, co-author of the article at the Universite Cote d’Azur, CNRS, Observatoire de la Cote d’Azur, Geoazur, Sofia-Antipolis, Valbon, France. .
“It was interesting to see that they could exist under very ‘exotic’ physical conditions [low gravity, no atmosphere] and similar, even compared to Mars.” OSIRIS-REx will return samples from Bennu to Earth on September 24, 2023.