Ever since Pluto got demoted from planet status, Mercury has been the runt of the Solar System. It’s got the shortest year of any planet, at just 88 days, and it’s roughly a third of the size of the Earth. But this tiny planet still has some big features. In a paper published in Geophysical Research Letters, researchers announced that they had found a massive valley on the planet’s surface.
Rembrandt valley is almost two miles deep in places and is 600 miles long and 250 miles wide. The Grand Canyon, for comparison, is only about one mile deep, about 277 miles long, and 18 miles wide at the widest spot.
“This is a huge valley. There is no evidence of any geological formation on Earth that matches this scale,” said Laurent Montesi, a co-author of the paper.
“Mercury experienced a very different type of deformation than anything we have seen on Earth. This is the first evidence of large-scale buckling of a planet.”
Montesi and his coauthors think that the valley formed between three and four billion years ago as the planet cooled and shrank, puckering the surface of the planet with large wrinkles. The valley shares a name with a nearby impact crater created when an asteroid slammed into the planet long ago.
The crater (or impact basin) was only noticed in 2008, when NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) space probe flew by the planet for the second time. Rembrandt valley was also noticed thanks to data from the MESSENGER spacecraft, which mapped the entire planet during its two years orbiting the planet. Researchers had to use stereo images, or images of the same location taken at different angles to get an accurate picture of how deep the valley actually is.