Mercury Is Shrinking, a ‘Great Valley’ Shows

Mercury Is Shrinking, a ‘Great Valley’ Shows

Mercury’s “great valley” appears dark blue in this image mosaic captured by NASA’s Messenger spacecraft.

NASA

A colossal canyon on Mercury may provide evidence that the tiny planet is shrinking.

Using data from NASA’s Messenger spacecraft, researchers have discovered a 620-mile-long, 250-mile-wide and 2-mile-deep valley on the planet’s southern hemisphere. It’s about the size of Montana and twice as deep as the Grand Canyon. In the elevation map above, the dark-blue chasm leads to a large purple crater known as the Rembrandt impact basin.

The researchers believe the “great valley” formed as Mercury’s interior cooled, which caused the planet’s crust and upper mantle to contract and bend. The findings appeared Wednesday in the journalGeophysical Research Letters.

Unlike Earth, which has multiple tectonic plates, Mercury’s lithosphere is made of a single plate. As it cooled, it buckled like a grape shriveling into a raisin.

Researchers are still piecing together all of the clues about how Mercury, the closest planet to the sun, cooled. Some scientists think it may have also undergone a more recent warming period after it formed.

Mercury might have shrunk by nearly nine miles in diameter in the past four billion years, according to previous research, and might still be getting smaller.