An Yin, a UCLA professor of Earth and space sciences, made the discovery by analysing over 100 satellite images of Mars, taken by a NASA spacecraft known as THEMIS (Time History of Events and Macroscale Interactions during Substorms) and from the HIRISE (High Resolution Imaging Science Experiment) camera on NASA's Mars Reconnaissance Orbiter. Yin explained to Mars Today:
"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... 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."
Yin has pointed out features that have been generated at fault lines — including cliffs and a very smooth, flat side of a canyon wall — as well as a linear volcanic zone, which all suggest the presence of tectonic plates. "You don't see these features anywhere else on other planets in our solar system, other than Earth and Mars," explains Yin. The results appear in the journal Lithosphere.
The evidence could explain the existence of the Mariner Valleys, whose existence have puzzled scientists for decades. Yin thinks that they are, in fact, a plate boundary. "The shell is broken and is moving horizontally over a long distance," he explained to Mars Today. "It is very similar to the Earth's Dead Sea fault system, which has also opened up and is moving horizontally."
He also suggests that Mars probably experiences earthquakes, too, though it's currently almost impossible to say how frequently — or how aggressive they are when they happen. That's partly due to the fact that Yin has so far only identified two tectonic plates on Mars, compared to Earth's seven, and doesn't know if others exist.
Yin hopes to dig deeper into the presence of Mars's new-found tectonic plates in the future. In the meantime, though, let's just hope Curiosity doesn't get caught out by a tremor. [Lithosphere via Mars Today]