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No plate tectonics, no high mountain ridges on Mars

It is remarkable that no plate tectonics (= a horizontal movement of the crust under influence of magma) have been observed on Mars. As a result, Mars has neither high mountain ridges nor deep troughs.

Where the Martian crust was thin enough, high volcanoes emerged where magma escaped. Lava also penetrated through fissures in the planet’s crust. There is very little volcanic activity on Mars, so we do not expect to see an eruption any time soon. We cannot, however, exclude hydrothermal activity on the planet.

Greenhouse Effect on Mars is far smaller than on Earth

The absence of plate tectonics also has consequences for the planet’s atmosphere. Chalky rocks absorb carbon dioxide from the atmosphere, as they do on Earth. But active volcanoes on Earth restore this carbon dioxide to the atmosphere. On Mars, however, this does not occur and there is not enough compounds susceptible to produce a noteworthy greenhouse effect in the Martian atmosphere. So the greenhouse effect on Mars is far smaller than on Earth.

Olympus Mons is a very large shield volcano on the planet Mars. The volcano has a height of nearly 26 km (Image credits Mars Orbiter Laser Altimeter (MOLA).