1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
2. Department of Astronomy, Cornell University, Ithaca, New York 14853, USA
3. Department of Earth and Space Science, University of California at Los Angeles, Los Angeles, California 90095, USA

Correspondence to: A. P. Ingersoll¹ Correspondence and requests for materials should be addressed to A.P.I. (e-mail: Email: api@gps.caltech.edu).

Jupiter's dominant large-scale weather patterns (dimensions 10,000 km) are zonal jets and long-lived ovals. The jets have been flowing east and west at constant speeds of up to 180 m s^-1 for over 100 years^{1, 2, 3}. These jets receive energy from small-scale eddies, which pump¹ eastward momentum into the eastward jets and westward momentum into the westward jets. This momentum transfer was predicted by numerical models⁴ before it was observed on Jupiter¹. The large ovals roll between the jets in an anticyclonic direction⁵—clockwise in the northern hemisphere and counterclockwise in the southern hemisphere—where they regularly assimilate small anticyclonic eddies^{5, 6}. But from where the eddies receive their energy has been an open question. Here we argue that the eddies, which ultimately drive both the jets and the ovals, receive their energy from moist convection. This hypothesis is consistent with observations of jovian lightning^{7, 8, 9}, which is an indicator of moist convection^{10, 11}. It also explains the anticyclonic rotation and poleward drift of the eddies⁵, and suggests patterns of upwelling and downwelling that resemble the patterns of large-scale axisymmetric overturning in the Earth's atmosphere.