The Mystery of Mars' Bizarre Plumbing

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.

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/31L6jffsLEo/the-mystery-of-mars-bizarre-plumbing

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