Experimental Study of Ethylene Evaporites under Titan Conditions

Titan has an abundance of lakes and seas, as confirmed by Cassini. Major components of these liquid bodies include methane (\(CH_4\)) and ethane (\(C_2H_6\)); however, evidence indicates that minor components such as ethylene (\(C_2H_4\)) may also exist in the lakes. As the lake levels drop, 5 \(\mu m\)-bright deposits, resembling evaporite deposits on earth, are left behind. Here, we provide saturation values, evaporation rates, and constraints on ethylene evaporite formation by using a Titan simulation chamber capable of reproducing Titan surface conditions (89-94 K, 1.5 bar \(N_2\)). Experimental samples were analyzed using Fourier transform infrared spectroscopy, mass, and temperature readings. Ethylene evaporites form more quickly in a methane solvent than in an ethane solvent or in a mixture of methane/ethane. We measured an average evaporation rate of \((2.8 \pm 0.3) \times 10^{-4} kg \; m^{-2} \; s^{-1}\) for methane and an average upper limit evaporation rate of less than \(5.5 \times 10^{-6} kg \; m^{-2} \; s^{-1}\) for ethane. Additionally, we observed red shifts in ethylene absorption bands at 1.630 and 2.121 \(\mu m\) and the persistence of a methane band at 1.666 \(\mu m\).