T72 125 Years Underground: A Retrospective and Prospective of Cave and Karst Research

Sunday, 27 October 2013
1:00 PM - 5:00 PM
Room 502

PLANETARY KARST

Paper number: T72-13
Program: Technical Sessions
Time: 4:05 PM – 4:20 PM

Authors

Abstract

Stretching the terrestrial definition, karst or dissolution geology can occur whenever there is a circulating fluid can dissolve a geological material. On Earth, the “classical” karst definition is for limestone (CaCO3) in water (H2O). But other material/solvent combinations can create terrestrial dissolution terrain as well. These include halite (NaCl)/H2O, gypsum (CaSO4)/H2O, dolomite (CaMg(CO3)2)/H2O, and even silica (SiO2)/H2O. On Mars, there has been the suggestion of kieserite (MgSO4)/H2O system that may have formed in an earlier, wetter environment.

Saturn’s moon Titan extends the karst definition to include non-aqueous planetary systems. The Cassini mission has provided evidence of a hydrocarbon-based cycle on Titan similar to the terrestrial water cycle. On Titan, recirculating hydrocarbon fluids may be capable of dissolving some of the surface organic molecules derived from Titan’s complex atmospheric photochemistry. Although under a different gravity, temperature, materials and fluid regime, many of the features on Titan’s surface bear striking resemblances to terrestrial karst terrains. This presentation will span the range of different materials, fluids, and planetary surfaces where dissolution processes have been invoked and identify the commonalities that may allow these processes to occur.

At it's core, karst starts as a chemical processes that is initiated when penetrating solvent molecules surround and lure away molecules that compose the cementing matrix or bulk material. As the dissolution process progresses, the host rock is weakened to the point that the physical process of erosion allows insoluble matrials to be transported away by moving fluids. For aqueous fluids, some ionic salts are the molecules most easily dissolved, but for hydrocarbon-based fluids, a subset of organic molecules may also be dissolved. The saturation equilibrium and kinetics of dissolution for each material and fluid combination may play key roles in determining how the karstic system will evolve.

We suggest that karst is a general planetary process wherever circulating fluids are capable of dissolving materials and developing subsurface drainage.