Radiocarbon on Titan

Abstract

We explore the likely production and fate of 14C in the thick nitrogen atmosphere of Saturn's moon Titan and investigate the constraints that measurements of 14C might place on Titan's photochemical, atmospheric transport and surface-atmosphere interaction processes. Titan's atmosphere is thick enough that cosmic-ray flux limits the production of 14C: absence of a strong magnetic field and the increased distance from the Sun suggest production rates of ~9 atom/cm^2/s, ~4x higher than Earth. The fate and detectability of 14C depends on the chemical species into which it is incorporated: as methane it would be hopelessly diluted even in only the atmosphere. However, in the more likely case that the 14C attaches to the haze that rains out onto the surface (as tholin, HCN or acetylene and their polymers), haze in the atmosphere or recently deposited on the surface would be quite radioactive. Such radioactivity may lead to a significant enhancement in the electrical conductivity of the atmosphere which will be measured by the Huygens probe. Measurements with simple detectors on future missions could place useful constraints on the mass deposition rates of photochemical material on the surface and identify locations where surface deposits of such material are "freshest".