On the clouds of uranus

Several models for the atmosphere of Uranus are considered. If the H₂ abundance is less than 250 km-am and the internal heat source is only a few percent of the total emitted energy then the cloud at the base of the atmosphere may be composed of solid CH₄ particles, while if the H₂ abundance is greater than 250 km-am or if the internal heat source is near the current upper limit of 35% of the total emitted energy the cloud at the base of the atmosphere may be composed of either solid NH₃ or H₂S particles.