Mars Canyon Formed When Plug Was Pulled, Study Suggests

Mars' great canyon complex, Valles Marineris, dwarfs the size and splendor of Earth's own Grand Canyon. But while geologists have a formed a fairly complete picture of how the Grand Canyon formed, the mechanisms that carved out Valles Marineris and its component canyons have been a longstanding mystery, with explanations ranging from massive floods to tectonic processes like those that cause earthquakes and build mountains on Earth.

"How did these gigantic canyons really form? Were they all formed by floods, or were other things going on?" asks John Adams of the University of Washington in Seattle and lead author of a new study that seeks to answer the questions. "These have been controversial questions going back to the very first Mariner pictures of Mars. And they're still controversial questions, which means we don't really fully understand what's going on yet."

The answer for how at least parts of the canyon complex formed may lie in Hebes Chasma, a 190-mile-long (310-kilometer) scar cut into the Martian surface and connected to the main body of Valles Marineris.

Adams and his colleagues, Alan Gillespie and David Montgomery, think that Hebes, and other chasms, might have formed after salts in the surface layers were heated up, causing water to melt out below the surface. This water then rushed out through underground plumbing, causing the layers of dirt and rock above to collapse, creating the canyon scar in the surface. link...