Planetary scientists have discovered a new valley on Mercury and it appears to be the first evidence of the outer shell buckling due to the planet’s shrinking.
Since the 1970s, astronomers have suspected Mercury has been contracting, but it’s only thanks to NASA’s MESSENGER spacecraft that we were able to establish that it has shrunk by almost 14 kilometers (8.7 miles) over the past billion years.
Researchers have previously discovered that Mercury’s crust and upper mantle, the so-called lithosphere, is tectonically active, although unlike Earth the small planet has a single plate. This buckling doesn’t come without its consequences, then. The latest analysis of the MESSENGER data reveals that as the core shrunk, the exterior of Mercury began to experience intense forces, which pushed parts of the crust upwards while the valley floor sunk downward.
The valley that has just been discovered is the result of this phenomenon. The valley is 1,000 kilometers (621 miles) long and 400 kilometers (250 miles) wide with a depth of 3 kilometers (2 miles), extending into the Rembrandt basin – the largest and youngest basin on Mercury. Their research was published in Geophysical Research Letters.
“There are examples of lithospheric buckling on Earth involving both oceanic and continental plates, but this may be the first evidence of lithospheric buckling on Mercury,” said lead author Thomas R. Watters, from the Smithsonian’s National Air and Space Museum, in a statement.
The valley is bound by two large cliffs that are the result of the same buckling mechanism. As the valley sank, the two scarps rose.
“Unlike Earth’s Great Rift Valley in East Africa, Mercury’s Great Valley is not caused by the pulling apart of lithospheric plates due to plate tectonics; it is the result of the global contraction of a shrinking one-plate planet,” Watters added. “Even though you might expect lithospheric buckling on a one-plate planet that is contracting, it is still a surprise when you find that it’s formed a great valley that includes the largest fault scarp and one of the largest impact basins on Mercury.”