14 DAY TRIAL // As a result of decades of studies, Mars' dichotomous landscape is now common knowledge for scientists. It is known, for instance, that the mountainous southern hemisphere rises some 6 km (3.73 miles) above the smooth northern one, and it's much thicker. This, together with the planet's peculiar magnetic field were thought to be the result of a large asteroid impact. But now a new theory sees this issue from a different perspective, one that would also explain the presence of the volcanic craters in the Tharsis Rise highlands.
US Scientist Shijie Zhong from the University of Colorado in Boulder believes the weird scenery is rather associated with some strange case of plate tectonics, never before observed in our solar system. On Earth, life depends on this process, as plates are constantly recycled – reabsorbed by the mantle and generated anew – and as volcanoes spew out life-regulating nutrients. Mars, which is approximately 6,794 kilometers (4,222 miles) in diameter, 53% that of the Earth, is considered to be too small in order to hold heat and host such activity for a longer period.
But, as the theory goes, this is not to say that nothing ever happened. Quite the contrary. Billions of years ago, claims Zhong, the entire crust was moving above the molten mantle, driven by an uneven convection. "Earth is the only planet with plates that move around," he shared, cited by Discovery. "But you can have the entire shell of crust rotating with respect to the interior." This caused the cooler material in the northern half to sink into the mantle, while hot material was pressed against the surface on the other hemisphere, thickening it and forming its tall features.
The crust moving southwards also caused the hottest stationary magma plume to emerge to the surface, breaching it as a series of volcanoes appearing in a row some 3.7 to 4.1 billion years ago and forming today's three volcanoes lined up on Tharsis Rise. In an attempt to prove this theory, which could also apply to many other bodies of the solar system, researchers will focus on crust fracture patterns, as well as on the magnetic signature of Mars' rocks.
"There may be a lot of other places in the solar system where this is important," explained Frances Nimmo from the University of California, in Santa Cruz. "Mercury, Venus, even some moons – almost everywhere you look outside of Earth you have single-plate bodies."