Friday, October 4, 2013

Martian Supervolcanoes

(From NASA/MOLA, via BBC News, used w/o permission.)
"Eden Patera is the best example. The irregular-shaped caldera formed when the ground collapsed into the void. The colours here represent elevation in the surrounding terrain. Red is high; blue is low"

"Supervolcanoes ripped up early Mars"
Jonathan Amos, BBC News (October 2, 2013)

"Mars may have had giant explosive volcanoes in its ancient past that spewed billions upon billions of tonnes of rock and ash into the sky.

"Vast areas of collapsed ground in a region of the planet called Arabia Terra are their likely remains, believe Joe Michalski and Jacob Bleacher....

Scientists kept finding evidence that really big volcanoes erupted when Mars was young, but hadn't found enough to account for all the ancient ash.

Apparently they were looking for the wrong kind of volcano.

Yellowstone Caldera and Mars

(From NASA/JPL/MSSS, via BBC News, used w/o permission.)
"An impact crater (L) is usually circular and surrounded by an apron of ejected material. The collapsed calderas of supervolcanoes (R) look very different, with volcanic features such as terracing and pinched rims"

"...They [Michalski and Bleacher] say such supervolcanoes would have had a profound impact on the early evolution of Mars.

"Their gases would have influenced the make-up of the atmosphere and perturbed the climate. And the ashfall would have covered the landscape across great swathes of the planet. It is quite likely some of the deposits the rovers are now encountering on Mars have their origin in colossal blasts...."
(Jonathan Amos, BBC News)

"Supervolcano" is an unofficial name for volcanoes that blow 1,000 cubic kilometers or more of rock into the air.

One of Earth's better-known supervolcanoes is the one that's powering Yellowstone Park's hot springs and geysers. That one probably has one more eruption coming. Not to worry, though. If the Yellowstone caldera's past eruptions are a guide, humanity probably has another 60,000 years to get ready: more or less.

The Yellowstone caldera doesn't look like a volcano, and neither do the Martian supervolcanoes. Olympus Mons was easy to spot: it's a huge mound with craters on top. What Michalski and Bleacher found look a little like irregular impact craters.

Part of what's different about the possible supervolcanoes on Mars is that, unlike craters left by impacts, they're deep.

If Michalski and Bleacher are right, scientists have part of the explanation for how parts of Mars got covered with so much ash. Understanding how Mars got to be the way it is should help settlers, when humanity gets around to moving outward, and that's another topic.

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