UNITED STATES: Researchers from NASA’s OSIRIS-REx discovered that the Sun’s radiation splits rocks on Bennu in about 10,000 to 100,000 years, showing that surface regeneration occurs much more quickly on asteroids than on Earth.
The scientists used high-resolution photos collected by the spacecraft OSIRIS-REx to analyse rock cracks on the asteroid Bennu for the findings (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer).
With this knowledge, scientists will be able to predict the time it takes boulders on asteroids like Bennu to fragment into smaller pieces, some of which may eject into space while others may remain on the asteroid’s surface.
Tens of thousands of years may seem like a long time, but Marco Delbo, a prominent scientist at Universite Cote d’Azur in France, said that, “We thought surface renewal on asteroids required a few millions of years.”
Geologically speaking, Delbo remarked, “We were startled to hear that the ageing and weathering process on asteroids happened so swiftly.”
Similar to how a cold glass breaks under hot water, rapid temperature variations on Bennu have caused internal stress that fractures and breaks down rocks.
On Bennu, the Sun rises every 4.3 hours. The equator has temperatures reaching over 127 Celsius during the day and roughly minus 23 Celsius at night.
In photographs taken by the spacecraft during the asteroid’s initial surveys, OSIRIS-REx scientists discovered fissures in the rocks. According to Delbo, the fractures appeared to all point in the same direction and were “A clear signal that temperature shocks between the day and the night may be the reason.”
The 10,000 to 100,000-year timescale for thermal fractures to spread and shatter rocks was calculated by the scientists using a computer model and their fracture readings.
The thermal fractures on Bennu, according to co-author Christophe Matonti of the study from Universite Cote d’Azur, CNRS, Observatoire de la Cote d’Azur, Geoazur, Sophia-Antipolis, Valbonne, France, “are quite comparable to what we observe on Earth and Mars in terms of how they occur.”
Even in comparison to Mars, “It is intriguing to see that they can exist and are similar in highly ‘strange’ physical settings” (low gravity, no atmosphere).
On September 24, 2023, OSIRIS-REx will send a sample back to Earth from Bennu.