Re: Why are Jupiter's clouds multicolored?

Indeed Jupiter's colors are flesh-toned to red in color, reflecting the
chemical compositions of the atmospheric layers.  However, the disk of 
Jupiter also shows bands of white, blue, and yellow clouds, also reflecting 
the various chemical compounds formed there.  The alternating strips of 
light and dark regions that run parallel to the equator are called zones 
and belts.  Infrared (IR) observations show that the zones have lower 
temperatures than the belts, and the differences in temperature imply that 
the zones mark the tops of rising regions of high pressure, while the belts 
mark the descending regions of low pressure.  The temperature variations 
also have some influence over the colors we see.

Lightning does occur on Jupiter and the photons (hv)[hv - h times nu is 
the energy of the photon] that result do influence chemical reactions.  
Some examples are as follows:

Making water (H2O):

O + hv -> O+ +e-
O+ + H2 -> OH+ + H
OH+ + H2 -> H2O+ + H
H2O+ + H2 -> H3O+ + H

and recombination causes H3O+ + e- -> H2O + H

Making ammonia (NH3): 

N + hv -> N+ + e-
N+ + H2 -> NH+ + H
NH+ + H2 -> NH2+ + H
NH2+ + H2 -> NH3+ + H
NH3+ + H2 -> NH4+ + H

and recombinatins causes NH4+ + e- -> NH3 + H

Methane (CH4) can be made in much the same way, starting with 
C + hv -> C+ + e-

IR analyses show that the atmosphere consists of methane, ammonia, 
molecular hydrogen (H2), and helium (He).  Acetylene, ethane, phosphine, 
water, and germane have also been detected.  By mass, Jupiter's atmosphere 
contains 78% hydrogen, 20% helium, and 2% all other elements, essentially 
the composition of the Sun.

The Red Spot is a few degrees cooler than the surrounding zone and a rising 
region of high pressure.  Its color probably results from chemical 
reactions of major and trace molecules, with photoionization (hv) and 
dissociation driving the reactions to make hydrocarbons that provide the 
coloration.


Reference:  Astronomy and Astrophysics (Zeilik and Gregory, 199) and notes 
from RPI's Origins of Life Course.