Titan tholin solubility in liquid ethane enhanced by intermediate isopentane solution

Solid organic particles, tholin, produced in Titan’s atmosphere come in contact with liquid methane and ethane through rain and in lakes on the surface. Laboratory investigation of the solubility of tholin with the surface hydrocarbons is difficult due to the low solubility in the non-polar, low-temperature liquids. Here we suggest an approach to bypass kinetic limitations by first using high-temperature non-polar hydrocarbons and then replacing the solvent with the cryogenic liquid. To test this, we have measured the solubility of Titan tholin in three solutions: A. isopentane at room temperature, B. liquid ethane at 91 K which was derived from the isopentane solution, and C. liquid ethane at 91 K. Our results suggest that there is considerable solubility of tholin in isopentane at room temperature and that a liquid ethane solution derived from that isopentane mixture retains up to 5% for specific solutes from the isopentane solution. In contrast, a solution from tholin mixed directly with liquid ethane contained much less solute. Further refined and tested, this approach could be of use for laboratory studies of tholin solubility. • Quantitative determination of the solubility of Titan tholin in liquid ethane and methane is necessary to understand the fluvial processes on Titan. • We propose here that dissolving Titan tholin in a room temperature non-polar hydrocarbon fluid and then replacing the fluid with the cryogenic ethane or methane fluid can accelerate the solubility.