Great Valley discovered by NASA on Mercury, indicates the planet is shrinking

NASA scientists have discovered a Great Valley in Mercury’s southern hemisphere. The discovery of Great Valley provides more evidence that Mercury, the closest planet to the sun, is shrinking.

A high-resolution topographic map was created by the scientists using the images from NASA’s Messenger spacecraft. The map revealed that the valley, which is more than 1,000 kilometres long, is extending into the Rembrandt basin, which is one of the largest and youngest impact basins on Mercury.

“Unlike Earth’s Great Rift Valley, 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,” said lead author of the study Tom Watters, senior scientist at the Smithsonian National Air and Space Museum in Washington, DC.

Mercury’s great valley is about 400 kilometres wide and three kilometres deep. It is smaller than Mars’ Valles Marineris but bigger than North America’s Grand Canyon and wider and deeper than the Great Rift Valley in East Africa, said the study published in the journal Geophysical Research Letters.

Two large fault scarps/cliff-like landforms that look like stair step bind the Mercury’s great valley. The study says that Mercury’s interior cooled and its shrinking was accommodated by the crustal rocks being pushed together, thrusting them upward along fault lines. As a result, the scarps were formed.

On August 3, 2004, NASA’s MErcury Surface, Space ENvironment, Geochemistry and Ranging (MESSENGER) mission was launched to study Mercury.