1. Institute for Astronomy, University of Hawaii, Honolulu, Hawaii 96822, USA
2. Lowell Observatory, Flagstaff, Arizona 86001, USA
3. Geological and Planetary Sciences,
4. Environmental Science and Engineering, California Institute of Technology, Pasadena, California 91125, USA

Correspondence to: E. L. Schaller¹ Correspondence and requests for materials should be addressed to E.L.S. (Email: schaller@ifa.hawaii.edu).

Abstract

Methane clouds, lakes and most fluvial features on Saturn's moon Titan have been observed in the moist high latitudes^{1, 2, 3, 4, 5, 6}, while the tropics have been nearly devoid of convective clouds and have shown an abundance of wind-carved surface features like dunes^{7, 8}. The presence of small-scale channels and dry riverbeds near the equator observed by the Huygens probe⁹ at latitudes thought incapable of supporting convection^{10, 11, 12} (and thus strong rain) has been suggested to be due to geological seepage or other mechanisms not related to precipitation¹³. 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.

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