Storms in the tropics of Titan
Methane clouds, lakes and most fluvial features on Saturn's moon Titan have been observed in the moist high latitudes while the tropics have been nearly devoid of convective clouds and have shown an abundance of wind-carved surface features like dunes. The presence of small-scale channels and dry riverbeds near the equator observed by the Huygens probe at latitudes thought incapable of supporting convection (and thus strong rain) has been suggested to be due to geological seepage or other mechanisms not related to precipitation. Here we report the presence of bright, transient, tropospheric clouds in tropical latitudes. We find that the initial pulse of cloud activity generated planetary waves that instigated cloud activity at other latitudes across Titan that had been cloud-free for at least several years. These observations show that convective pulses at one latitude can trigger short-term convection at other latitudes, even those not generally considered capable of supporting convection, and may also explain the presence of methane-carved rivers and channels near the Huygens landing site.
Additional Information© 2009 Nature Publishing Group. Received 5 March; accepted 2 June 2009. E.L.S. is supported by a Hubble Postdoctoral Fellowship. H.G.R is supported by the NASA Planetary Astronomy Program. M.E.B. is supported by an NSF Planetary Astronomy grant. We thank IRTF telescope operators, D. Griep, W. Golisch, P. Sears and E. Volquardsen. The IRTF is operated by the University of Hawaii under a cooperative agreement with the Planetary Astronomy Program of the NASA Science Mission Directorate. Gemini Observatory is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the International Gemini partnership. Author Contributions: E.L.S. analysed and interpreted the IRTF and Gemini observations and wrote the paper. H.G.R. was responsible for the Gemini observations, data reduction, and analysis. T.S. helped interpret the observations. T.S. and E.L.S. wrote the Supplementary Information. M.E.B. supervised the project. All authors discussed the results and implications and commented on the manuscript.
Supplemental Material - Schallernature08193-s1.pdf