December 17, 2014

13.05.10: Finding Martian Lava Tubes.

(Credit: Jim Secosky NASA/JPL/ASU).

(Credit: Jim Secosky NASA/JPL/ASU).

Martian lava tubes as seen by THEMIS. 

   A key hunt on the Martian surface is underway. Since the Pathfinder series of landers in the mid-90’s, NASA’s mantra has been to Follow the Water. Scouring the surface of Mars, we see signs of ancient water erosion, as evinced by complex braidings, channels and scarps…

Or is it? Up until recently, it’s been thought that only water could produce such complex features. Now, researcher Jacob Bleacher of NASA’s Goddard Space Flight Center in Greenbelt Maryland has analyzed grooved channels on the flank of Ascraeus Mons, one of the three famous mountains in the Tharsis Montes chain of volcanoes, of which Olympus Mons is a member. Some of the highest peaks in the solar system, these extinct volcanoes are of the shield variety. Earlier photographic analysis suggested that the channels on the ramparts of Ascraeus were the result of water erosion on ancient Mars. But analysis by Bleacher utilizing a battery of instruments aboard Mars Odyssey, including the Thermal Emission Imaging System (THEMIS) revealed an interesting puzzle; although the initial origin point of the channel looked like it was formed by water, action further down the chain was highly suggestive of collapsed lava tubes (above). A hybrid water-lava eroded channel is highly unlikely…a single cause of formation by lava is simpler and much more plausible. Colleague Andy de Wet has spied even more curious features; “the channel is actually roofed over as if it were a lava tube, and lined up along this are several rootless vents.” Evidence throughout the solar system is mounting that lava flows may mimic water erosion; on our bone dry (for the purposes of this discussion!) airless Moon, evidence of ancient lava flows is seen around the Mare Imbrium, and on Earth, complex slow moving flows have carved intricate structures seen and studied around Mauna Loa, Hawaii. These findings may serve as a caveat that all that looks like evidence of water on Mars, perhaps isn’t… areas such as the Ascraeus Plateau beg for further exploration. So, just when will we be able to take a day-hike down these ancient lava tubes, and ponder (and blog about) their origins in person?