Experimental determination of acetylene and ethylene solubility in liquid methane and ethane: Implications to Titan’s surface

In this study, the solubility of acetylene (or ethyne, C2H2) and ethylene (or ethene, C2H4) in liquid methane (CH4) and ethane (C2H6) has been experimentally determined at Titan surface temperature (90 K) and pressure (1.5 bars). As predicted by theoretical models, the solubilities of acetylene and ethylene are very large at Titan temperature and these species are most likely to be abundantly present in the lakes and as evaporites on the shores or dry lake beds. Our results indicate the solubility of 4.9 × 10−2 mole fraction for acetylene in methane and 48 × 10−2 mole fraction in ethane; for ethylene, 5.6 × 10−1 mole fraction in methane and 4.8 × 10−1 mole fraction in ethane. Assuming the mole fractions from atmospheric models in the lower stratosphere and equilibrium with the surface, we determined that the lakes on Titan that cover ∼400,000 km2 are not saturated. The liquid lakes on Titan act as an important reservoir for both acetylene and ethylene. Assuming difference of methane and ethane content in the lakes at different latitudes, the difference in solubility in liquid methane and ethane, solutes in lakes may change with the temporal evolution (such as; evaporation and condensation) over seasons and geological time scales.