Future Missions to Titan: Scientific and Engineering Challenges

ASN Ambient seismic noise BiCMOS Bipolar junction complementary metal-oxide-semiconductor CCN Cloud condensation nuclei CE Capillary electrophoresis CNT Carbon nanotube CTE Coefficient of thermal expansion DAP Diallyl phthalate DOSY Diffusion ordered spectroscopy FID Flame ionization detector FT-ICR Fourier transform-ion cyclotron resonance GaAs Gallium arsenide GC Gas chromatography InP Indium phosphide IC Integrated circuits LC Liquid chromatography MEMS Microelectromechanical system MER Mars Exploration Rovers (NASA) µTAS Micro-total-analysis systems MSL Mars Science Laboratory (NASA) NMR Nuclear magnetic resonance PAH Polycyclic aromatic hydrocarbon PMT-PT Lead magnesium niobate/lead titanate crystal (low-T piezo material) PSN-PT Lead scandium niobate/lead titanate crystal (low-T piezo material) PTFE Polytetrafluoroethylene (Teflon) RHU Radioisotope heater unit RTG Radioisotope thermoelectric generator SAM Sample Analysis on Mars (MSL) SEM Scanning electron microscopy SiGe Silicon germanium SP Short period SPU Sample processing unit TAG Thermal desorption aerosol GC/MS-FID TCR Thermal coefficient of resistance TEG Thermo electric generator TOF Time of flight TRL Technology readiness level UHV Ultra-high vacuum ULE Ultra-low expansion VBB Very broad band VCAM Vehicle Cabin Atmosphere Monitor (NASA) 5 1. Executive summary Saturn's largest moon, Titan, has been an enigma at every stage of its exploration. For three decades after the hazy atmosphere was discovered from the ground in the 1940s, debate ensued over whether it was a thin layer of methane or a dense shield of methane and nitrogen. Voyager 1 settled the matter in favor of the latter in 1980, but the details of the thick atmosphere discovered raised even more intriguing questions about the nature of the hidden surface, and the sources of resupply of methane to the atmosphere. The simplest possibility, that an ocean of methane and its major photochemical product ethane might cover the globe, was cast in doubt by Earth-based radar studies and then eliminated by Hubble Space Telescope and adaptive optics imaging in the near-infrared from large ground-based telescopes in the 1990s. These data, however, did not reveal the complexity of the surface that Cassini-Huygens would uncover beginning in 2004. A hydrological cycle appears to exist in which methane (in concert with ethane in some processes) plays the role on Titan that water plays on Earth. Channels likely carved by liquid methane and/or ethane, lakes and seas of these materials—some rivaling or exceeding North America's Great Lakes in size—vast equatorial dune fields of complex organics made high in the atmosphere and shaped by wind, and intriguing hints of geologic activity suggest a world with a …