Title: Upper limit of hydrogen and helium concentrations on Titan
Abstract: The satellite Titan is commonly quoted as possessing an atmosphere consisting of at least 2 × 10 4 cm atm of methane. Plausible additional atmospheric constituents like hydrogen and helium are assumed to have completely escaped from the satellite. However, the employment of recent techniques to the upper atmosphere of Titan permits an improved estimate of the upper limits of the hydrogen to methane and helium to methane mixing ratios existing in the lower atmosphere of Titan, namely 10 −6±1 and 10 −3.5±0.5 .