Supervolcanes discovered on Mars

New class of volcanism sheds new light on the early days of the planet

The Calderies of Eden Patera (Dark) - Traces of a Primeval Super-Volcan © NASA / JPL / GSFC / Arizona State University
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Mars is known for its gigantic mountains of fire. So far, they have been considered the typical and only volcanic form of the planet. But now researchers have discovered another, completely new type of volcano there: subconscious hidden super volcanoes. About 3.5 billion years ago, they could have spewed thousands of cubic kilometers of magma with each eruption. This find could change our entire idea of ​​volcanism on Mars, say the scientists in the journal "Nature".

Super volcanoes are in a class of their own: most of them are in no way similar to the normal, shield or conical fire mountains. Instead, they hide under the ground. There ascending magma from the earth's mantle feeds a particularly large magma chamber in which magma and volcanic gases collect. When a critical amount is reached, the super volcano breaks out. He hurls more than 1, 000 cubic kilometers of lava, ash and boulders at supersonic speeds. The force of the eruption causes the crust to break over the Magmenkammer, leaving behind a large crater. Such an active super volcano is located, for example, under the Yellowstone National Park in the USA.

There must be others ...

Up to now only one type of volcano has been known on our neighbor planet Mars: huge shield volcanoes like the towering Olympus Mons. "But these mountains of fire are relatively young and we've always wondered where the ancient primeval volcanoes are, " explains Joseph Michalski of the Natural History Museum in London. Especially near the Martian equator there are thick layers of fine-grained material resembling volcanic deposits. But her source remained enigmatic.

"There must be undiscovered volcanic regions on Mars, " mused Michalski and his colleague Jacob Bleacher of NASA. Therefore, they set out to search. For their study, the researchers evaluated data from various Mars probes, including the Mars Express, the Mars Reconnaissance Orbiter and Mars Global Surveyor. These not only allowed the exact analysis of the height profile and structure of different regions of Mars, but also provided information about the chemical composition of the subsurface.

Schr ger Blick about the topography of Eden Patera ESA / Mars Express / Free University of Berlin

Suspicious structures in Arabia Terra

And indeed: In the region of Arabia Terra, the researchers come across suspicious structures: a collection of large, irregularly shaped craters in the midst of a highland stratified by stratified deposits. One of them in particular, Eden Patera, was striking, as they report: it is around 55 kilometers wide, 85 kilometers long and strikingly deep: its bottom is 1.8 kilometers below the surrounding terrain. So far, this complex of three interconnected sinks was usually considered impact crater. However, the shape of the crater walls and the missing central mountain are rather untypical for this, in addition, the craters are significantly deeper than comparable impact structures, as the scientists explain. display

On closer examination of this area, Michalski and Bleacher also came across some structures that did not at all fit in with a meteorite impact: for example, they discovered two terraced slopes at the crater rim, 100 and 150 meters above the bottom of the valley. Their shape and size are surprisingly similar to the terraces known from terrestrial lava lakes, the researchers explain. They arise when a lava border solidifies on the edge of such a reservoir. If then the level of this lava lake sinks, this lava edge stops. For a volcano caldera also speaks another indication: In the craters numerous dislocations go through the crust. The researchers interpret them as cracks that occurred when the ceiling washes over a magma chamber. The scientists discovered similar structures in several other craters of the Arabia Terra region.

Layered deposits and collapse structures at the bottom of Eden Patera point to an ancient lava lake. NASA / JPL / MSSS / Google

All new class of Mars volcanism

"Taken together, these structures form a whole new class of Mars volcanoes - primeval super volcanoes that together threw out gigantic amounts of lava and pyroclastic material, " states Michalski and Bleacher. These superculkanes were believed to have been active around 3.5 billion years ago and could have affected the entire territory of Arabia Terra at that time. Researchers estimate that each of the caldera complexes in this region has ejected up to 7, 200 cubic kilometers of lava, ash and boulders. For comparison, the largest eruption of the terrestrial Yellowstone supercooler some two million years ago probably only brought about 1, 300 cubic kilometers of material.

"Discovering such supervulcan structures fundamentally changes our view of Mars volcanism, " says Michalski. If even more superculcans are discovered on the Red Planet, this also changes previous assumptions about how the early Martian atmosphere originated, how deposits formed - and last but not least, how habitable and life-friendly the young Mars was once. (Nature, 2013; doi: 10.1038 / nature12482)

(Nature, 04.10.2013 - NPO)