Using the stereo images from NASA's MErcury Surface, Space ENvironment, GEochemistry and Ranging, or most commonly known as MESSENGER, spacecraft to create a high-resolution topo map, the scientists were able to identify the so called "Great Valley." The newly-found Great Valey was found in the Mercury wherein it indicates that the planet is shrinking. 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.
The Planet Mercury
Mercury is the smallest and innermost planet in the Solar System. Its orbital period is less than any other planet in the Solar System. Seen from Earth, it appears to move around its orbit in about 116 days. It has no known natural satellites. Because Mercury orbits the Sun within Earth's orbit (as does Venus), it can appear in Earth's sky in the morning or the evening, but not in the middle of the night. Two spacecraft have visited Mercury: Mariner 10 flew by in 1974 and 1975; and MESSENGER, launched in 2004, orbited Mercury over 4,000 times in four years.
Great Valley Found; Planet Mercury Is Shrinking
According to The Siasat Daily, scientists have discovered a “great valley” in the southern hemisphere of Mercury, providing more evidence that the small planet closest to the sun is shrinking. They used images from NASA’s MESSENGER spacecraft to create a map that revealed the valley. About 400 km wide and three km deep, Mercury’s great valley is smaller than Mars’ Valles Marineris, but larger 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.
“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 Tom Watters, senior scientist at the Smithsonian National Air and Space Museum in Washington, DC. The Great Valley is bound by two large cliff-like landforms. The scarps formed as Mercury’s interior cooled and the planet’s shrinking was accommodated by the crustal rocks being pushed together, thrusting them upward along fault lines, the study said.
