1. Service d'Aéronomie, B102, Université de Paris 6/Université de Versailles-St-Quentin, 4 place Jussieu, 75252 Paris Cedex, France
2. Laboratoire de Météorologie Dynamique, Université de Paris 6, 4 place Jussieu, 75252 Paris Cedex, France
3. NASA-Ames Research Center, Moffett Field, California 94035, USA

Correspondence to: P. Rannou¹ Correspondence and requests for materials should be addressed to P.R. (e-mail: Email: pra@ccr.jussieu.fr).

Abstract

Titan, the largest moon of Saturn, is the only satellite in the Solar System with a dense atmosphere. Titan's atmosphere is mainly nitrogen with a surface pressure of 1.5 atmospheres and a temperature of 95 K (ref. 1). A seasonally varying² haze, which appears to be the main source of heating and cooling that drives atmospheric circulation^{3, 4}, shrouds the moon. The haze has numerous features that have remained unexplained. There are several layers⁵, including a 'polar hood'^{6, 7, 8}, and a pronounced hemispheric asymmetry². The upper atmosphere rotates much faster than the surface of the moon^{9, 10}, and there is a significant latitudinal temperature asymmetry at the equinoxes^{11, 12}. Here we describe a numerical simulation of Titan's atmosphere, which appears to explain the observed features of the haze. The critical new factor in our model is the coupling of haze formation with atmospheric dynamics, which includes a component of strong positive feedback between the haze and the winds.

1. Service d'Aéronomie, B102, Université de Paris 6/Université de Versailles-St-Quentin, 4 place Jussieu, 75252 Paris Cedex, France
2. Laboratoire de Météorologie Dynamique, Université de Paris 6, 4 place Jussieu, 75252 Paris Cedex, France
3. NASA-Ames Research Center, Moffett Field, California 94035, USA

Correspondence to: P. Rannou¹ Correspondence and requests for materials should be addressed to P.R. (e-mail: Email: pra@ccr.jussieu.fr).