Mercury is still shrinking after billions of years, and scientists can see its ‘wrinkles’

The smallest planet in the solar system is getting even smaller. Mercury, the closest planet to the sun, has been cooling down and contracting for millennia, creating gigantic scars on its surface (known as lobate scarps) as the rocky surface buckles from the shrinkage.

Geologists weren’t sure when exactly these scarps formed, or if Mercury’s still making new ones as it continually cools — until now. New research published Oct. 2 in the journal Nature Geoscience took a closer look at the scarps, and found small cracks indicating that they must have moved in the last 300 million years.