Atmospheres of Jupiter and Saturn
The clouds we see are mostly ammonia. Talk about the most common elements: H,He,C,N,O. He is inert. H forms molecules with the others: 0H_2 (water), NH_3 (ammonia), CH_4 (methane). These are among the most common molecules around (along with forms involving C + O or N). Note that there are layers with room temperature water clouds (and only a few atmospheres pressure). We don’t understand the trace constituents that give the clouds color. The temperature keeps increasing toward the interior.