Fumarolic Activity Patterns as Indicators of Pre-Flow Archaeology of Underlying Terrain Features: Lessons Learned from Field Observations on Mauna Ulu During BASALT Deployment.

Field observations were conducted around the southwestern slope of Mauna Ulu in the Hawaii Volcanoes National Park as part of the NASA PSTAR grant BASALT (Biologic Analog Science Associated with Lava Terrains, Conops Development for Future Human Exploration of Mars). While mapping areas with signs of hydrologically altered basalts and their associated minerology, a curious pattern of active and inactive fumaroles became obvious during the mapping. Initially labeled a "Fairy ring" (after circular mushroom growth patterns), these fumaroles were found to overlay the edges of obscured pit craters that pre-dated the 1969-74 eruption of Mauna Ulu. Both Alae and Alo'i craters were filled completely by the extensive Mauna Ulu flows.

We believe that when the craters were filled, the margins of the existing crater walls were the weakest points for gasses and heat to escape the slowly cooling lava mass, which filled in the craters, like a plug analogous to a cork in a bottle. Thus the fumaroles mark the location of the buried rims of these earlier craters. This means of tomography is labeled by us as "Volcanic Archeology."

Applications to other rocky planets with volcanism. Mars Exploration Rover (MER) Spirit observations in Gusev Crater of a formation named "Home Plate" is suspected to be the eroded remains of an ancient and extinct fumarole. It is suggested that attention be paid to the patterns and relative locations of future extinct fumaroles on Mars as possible indicators of buried topology caused by prior eruptions or remants of impact craters.