An estimate of the chemical composition of Titan's lakes

TL;DR

This paper estimates the chemical composition of Titan's lakes using data from the Huygens probe and photochemical models, revealing a dominant ethane presence and differences from prior expectations.

Contribution

It provides the first detailed composition estimates of Titan's lakes based on direct measurements and thermodynamic modeling, updating previous models.

Findings

Lakes are mainly ethane (~76-79%)

Presence of propane, methane, HCN, butene, butane, and acetylene

Composition differs significantly from pre-Cassini models

Abstract

Hundreds of radar-dark patches interpreted as lakes have been discovered in the north and south polar regions of Titan. We have estimated the composition of these lakes by using the direct abundance measurements from the Gas Chromatograph Mass Spectrometer (GCMS) aboard the Huygens probe and recent photochemical models based on the vertical temperature profile derived by the Huygens Atmospheric Structure Instrument (HASI). Thermodynamic equilibrium is assumed between the atmosphere and the lakes, which are also considered as nonideal solutions. We find that the main constituents of the lakes are ethane (C2H6) (~76-79%), propane (C3H8) (~7-8%), methane (CH4) (~5-10%), hydrogen cyanide (HCN) (~2-3%), butene (C4H8) (~1%), butane (C4H10) (~1%) and acetylene (C2H2) (~1%). The calculated composition of lakes is then substantially different from what has been expected from models elaborated prior to the exploration of Titan by the Cassini-Huygens spacecraft.