Science, Vol 269, Issue 5231, 1697-1699
Copyright © 1995 by American Association for the Advancement of Science
Condensation of methane, ammonia, and water and the inhibition of convection in giant planets
T Guillot
Lunar and Planetary Laboratory, University of Arizona, Tucson 85721, USA.
The condensation of chemical species of high molecular mass such as methane, ammonia, and water can inhibit convection in the hydrogen-helium atmospheres of the giant planets. Convection is inhibited in Uranus and Neptune when methane reaches an abundance of about 15 times the solar value and in Jupiter and Saturn if the abundance of water is more than about five times the solar value. The temperature gradient consequently becomes superadiabatic, which is observed in temperature profiles inferred from radio-occultation measurements. The planetary heat flux is then likely to be transported by another mechanism, possibly radiation in Uranus, or diffusive convection.
