Olympus Mons – Mars’ Volcano
Mars has the largest volcano in the solar system – Olympus Mons. It measures some 600 kilometres across and rises nearly 27 kilometres above the surrounding terrain. It is a shield volcano built by the continuous action of flowing lava over millions and millions of years that began some 3 billion years ago. Olympus Mons is part of a complex of volcanoes that lie along a volcanic plateau called the Tharsis Bulge. This entire region lies over a hotspot, a place in the planet’s crust that allows magma from deep inside to flow out to the surface. While planetary scientists have not recorded a volcanic eruption on Mars in real time, there is evidence of geologically recent flows perhaps in the past few tens of millions of years. It is possible that Mars is not yet volcanically dead.
Valles Marineris – Mariner Valleys
The Valles Marineris is an extensive canyon system on the Mars equator. It is 4,200 kilometres long and, in places, is 7 kilometres deep. If you placed this canyon on Earth, it would span the North American continent and slightly beyond. The planet has a very primitive form of plate tectonics, and the action of two plates past each other began splitting the surface some 3.5 billion years ago. That set the stage for the formation of the Valles Marineris. At the same time, volcanic activity in the Tharsis region put pressure on the crust as molten lava pushed the region up from below. The combined tectonic activity further broke the crust into fractures and fault regions. In the valleys, the ground sank, and underground water escaped. That caused the ground to drop farther, and landslides and erosion continued to cut away and widen the valley systems. Today, the Vallis Marineris canyons show the marks of ancient floods and continued erosion by the Martian winds.
Noctis Labyrinthus – The Labyrinth of the Night
One of the most intriguing features on Mars is the Noctis Labyrinthus. It lies between the Tharsis Bulge and Valles Marineris and is really a giant maze of canyons, troughs and pits. Planetary scientists refer to it as “chaotic terrain”. This region is caught between two tectonically active regions of Mars. Volcanic activity put tremendous stress on the landscapes east of the Tharsis volcanoes. The slow motions of Mars’s primitive subsurface plates that split the crust and formed the Valles Marineris carved out Labyrinth’s first canyons. As the ground was heated and cracked, subsurface water and ice escaped in catastrophic outflows swept out rocks and boulders and caused the ground to collapse. Today, the Noctis Labyrinthus pays silent tribute to the power of tectonic forces combined with action of escaping water.
The Martian Polar Ice Caps
Mars has two ice caps that grow and shrink with the change of seasons. Both caps are made primarily of water ice, but the south polar cap is always covered with frozen carbon dioxide – dry ice. The larger of the two caps lies at the north pole. At its largest, the permanent north polar cap stretches across about 1,100 kilometres. It accumulates carbon dioxide ice during its winter, but loses that ice to the atmosphere during the rest of the Mars year. The permanent south polar cap is only about 400 kilometres across and also accumulates more carbon dioxide ice during its winter. Both caps also have deposits of Martian dust, which are deposited during dust storms. Planetary scientists suspect that the layers of dust and ice in both caps hold important clues to how the climate has changed over Mars’s lifetime.