On Mars, signs of huge volcanoes

Early Mars was an explosive, fiery place, much like early Earth, with supervolcanoes that could eject at least 240 cubic miles of molten rock.

Drawing on images and data from the Mars Express and Global Surveyor spacecrafts, scientists identified irregular craters in an upland region in northern Mars, called Arabia Terra, that were formed through massive explosions and subsequent collapses. Those structures are remnants of supervolcanoes, much like the one at Yellowstone National Park that has erupted multiple times in the last 18 million years, according to a paper in the journal Nature.

Supervolcano explosions on Mars may explain the fine-grained deposits on the planet. Scientists had previously suggested these materials might have come from volcanic eruptions, though no volcanoes had been recognized in the region until now. Knowing the nature of early, widespread volcanic activity will also aid researchers in determining if Mars was once habitable.

"Volcanism is the thread binding nearly every aspect of Mars' geologic evolution," Joseph Michalski, the study author and a Mars researcher at the National History Museum in London and the Planetary Institute in Tucson, Ariz., said in a statement. "The better we understand volcanism on Mars, the better we can understand the planet."

On Earth, all supervolcano eruptions occurred tens of thousands to millions of years ago, according to the U.S. Geological Survey.

Mars is already known to have shield volcanoes, which are much younger volcanoes and similar to those in Hawaii. Olympus Mons is the largest active volcano on Mars, and is 100 times larger than Mauna Loa.

With the size of the craters' depressions as a guide to how much rock was expelled, the average minimum eruption spewed 1,100 to 1,700 cubic miles of debris.

Yellowstone's most recent eruption, 640,000 years ago, was a thousand times the size of the 1980 Mount St. Helens eruption in Washington state. Ash from its giant eruptions occurring between 2.1 million and 640,0000 years ago is spread from California to Iowa, and from Canada to the Gulf of Mexico.