The Mystery of Mars' Bizarre Plumbing 62
astroengine writes "Hesperia Planum: once a Martian plain — a regular, no-surprises, run-of-the-mill plain. But now, thanks to researchers who used high-resolution imagery from the armada of satellites currently orbiting the Red Planet, Hesperia Planum holds a mystery. Sinuous rilles, a common feature in ancient volcanic regions on Mars and the Moon, appear across Hesperia, but they appear to have no origin and no destination. If they were formed by lava flows, wouldn't they originate near volcanoes? This oddity has led Tracy Gregg and her student Carolyn Roberts of the University at Buffalo to postulate an entirely different rille formation process that could make Hesperia Planum a whole lot more interesting than scientists ever thought."
Re:Shield Volcanos? (Score:5, Interesting)
I don't know much about the geology, but could it possibly be the result of a shield volcano?
That's basically the current/default understanding - the rilles were created from subsurface flows of lava that left empty lava tubes, which collapsed leaving the rilles behind. Similar to what you see, on a much smaller scale, in places like Lava Beds on the Modoc plateau in Northern California.
This study points out that some of the rilles don't appear to really be starting or ending at identifiable volcanic vents/craters, and so they are questioning whether they are actually the result of volcanic activity. If you take a look at this photo [geosociety.org], you can sort of see what they mean. The feature pointed out with the arrows looks a lot more like a stream bed than it does a collapsed lava tube. It is hard to really form a strong opinion from the photo, though; it is difficult to tell if the feature is actually following topography like a gravity flow.