PX282 - K4 - atmosphere

• the composition is mainly the H and He envelope, enriched in CH${}_4$, NH${}_3$ (also H${}_2$O)

jupiter

image: leigh fletcher, ESO

• distinct bands of bright zones*, with reflective clouds of ammonia ice, and dark belts*, with red/brown colour from molecules formed by UV photosensitivity with deeper visibility
• in thermal infrared, the banding pattern is reversed as high altitude clouds are cold and dark
• the cloud-free belts are brighter because it probes deeper, into higher temperatures
• clouds in zones condense as warm material rises and cools in convection pattern
• the clouds evaporate in dark belts as they sink and the temperature rises
• rising and north-south spreading in convection bands carries angular momentum and results in strong local over/under rotation, ie. east-west winds
• many storms at the shearing boundaries, including the great red spot

image: fundamental planetary science

saturn

image: Cassini probe, NASA

• has a similar banding pattern to jupiter, but is muted because the clouds form deeper, in the colder atmosphere
• occasional storms bring reflective NH${}_3$ clouds to higher altitudes

uranus

image: voyager 2, NASA

• almost featureless, blue due to methane abundance
• very faint banding
• later, strong white clouds were visible, possibly due to seasonal variations

image: voyager 2, NASA (false colour)

neptune

image: voyager 2, NASA

• colder with deeper NH${}_3$ ice clouds, with more muted banding
• the blue colour is from enhanced methane abundance, which strongly absorbs red optical light
• high altitude white clouds from methane ice condensing at these low temperatures

image: fundamental planetary science