Sun keeps some asteroids looking young, finds NASA's OSIRIS-REx mission

Surface regeneration happens a lot quicker on asteroids than on Earth, according to a new study by a team of scientists from NASA's OSIRIS-REx mission, who analyzed rock fractures on near-Earth asteroid Bennu from high-resolution images taken by the spacecraft. The team discovered that the Sun's heat fractures rocks on Bennu in just 10,000 to 100,000 years.

The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, short for OSIRIS-REx, is a NASA mission that travelled to Bennu and collected a sample of rocks and material from the surface that it will return to Earth in 2023.

"Tens of thousands of years might sound pretty slow, but we thought surface regeneration on asteroids took a few millions of years. We were surprised to learn that the aging and weathering process on asteroids happens so quickly, geologically speaking," said Marco Delbo, senior scientist at Université Côte d'Azur, CNRS, Observatoire de la Côte d'Azur, Laboratoire Lagrange, Nice, France, and lead author of a paper published June 2022 in Nature Geoscience.

According to NASA, rapid temperature changes on Bennu create internal stress that fractures and breaks down rocks.

Delbo and his colleagues mapped more than 1,500 rock fractures in OSIRIS-REx images and found that the fractures predominantly align in the northwest-southeast direction, indicating they were caused by the Sun, which is shown here to be the primary force changing asteroid Bennu's landscape.

The team used a computer model and their fracture measurements to calculate the 10,000 to 100,000-year timeframe for thermal fractures to propagate and split rocks.

"Keep in mind, the topography of Bennu is young, but the rocks on the asteroids are still billions of years old and hold valuable information about the beginning of the solar system," noted Jason Dworkin, OSIRIS-REx project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Don't forget to wear sunscreen. Some asteroids are aged early by the Sun, with surface rocks fracturing in just 10,000-100,000 years. Analysis of images from our #OSIRISREx mission revealed a weathering process that happens fast, geologically speaking: https://t.co/EupmNjFsKe pic.twitter.com/gFfkIhQXgV

— NASA (@NASA) July 24, 2022