A planetary geologist from the University of California in Los Angeles has discovered the first strong evidence that the geological phenomenon known as plate tectonics exists on the Red Planet.
“Mars is at a primitive stage of plate tectonics. It gives us a glimpse of how the early Earth may have looked and may help us understand how plate tectonics began on Earth,” said Prof An Yin, sole author of the new research published in the August issue of the journal Lithosphere.
Prof Yin made the discovery during his analysis of satellite images from NASA’s THEMIS spacecraft and Mars Reconnaissance Orbiter. He analyzed about 100 satellite images – approximately a dozen were revealing of plate tectonics.
The scientist has conducted geologic research in the Himalayas and Tibet, where two of the Earth’s seven major plates divide. “When I studied the satellite images from Mars, many of the features looked very much like fault systems I have seen in the Himalayas and Tibet, and in California as well, including the geomorphology,” said Prof Yin.
For example, he saw a very smooth, flat side of a canyon wall, which can be generated only by a fault, and a steep cliff, comparable to cliffs in California’s Death Valley, which also are generated by a fault. Mars has a linear volcanic zone, which Prof Yin said is a typical product of plate tectonics.
“You don’t see these features anywhere else on other planets in our Solar System, other than Earth and Mars,” said Prof Yin.
The surface of Mars contains the longest and deepest system of canyons in our solar system, known as Valles Marineris. It is nearly 2,500 miles long – about nine times longer than the Earth’s Grand Canyon. Scientists have wondered for four decades how it formed. Was it a big crack in Mars’ shell that opened up?
“In the beginning, I did not expect plate tectonics, but the more I studied it, the more I realized Mars is so different from what other scientists anticipated,” Prof Yin said. “I saw that the idea that it is just a big crack that opened up is incorrect. It is really a plate boundary, with horizontal motion. That is kind of shocking, but the evidence is quite clear. The shell is broken and is moving horizontally over a long distance. It is very similar to the Earth’s Dead Sea fault system, which has also opened up and is moving horizontally.”
“The two plates divided by Mars’ Valles Marineris have moved approximately 93 miles horizontally relative to each other,” Prof Yin explained. California’s San Andreas Fault, which is over the intersection of two plates, has moved about twice as much — but the Earth is about twice the size of Mars, so Yin said they are comparable.
Prof Yin calls the two plates on Mars the Valles Marineris North and the Valles Marineris South.
“Earth has a very broken ‘egg shell,’ so its surface has many plates; Mars’ is slightly broken and may be on the way to becoming very broken, except its pace is very slow due to its small size and, thus, less thermal energy to drive it,” Prof Yin said. “This may be the reason Mars has fewer plates than on Earth.”
Mars has landslides, and Prof Yin concluded a fault is shifting the landslides, moving them from their source.
Bibliographic information: An Yin. 2012. Structural analysis of the Valles Marineris fault zone: Possible evidence for large-scale strike-slip faulting on Mars. Lithosphere, v. 4 no. 4 p. 286-330; doi: 10.1130/L192.1