Dua is a carbon planetoid devoid of water, yet it constantly rains on the surface. As the comets and asteroids delivered water though the ages, the carbon on the surface reacted with the water causing it to evaporate.
The atmosphere of Dua consist primarily of carbon dioxide and methane that consist of thick hazy misty clouds. The land is dotted with rivers and lakes that consist of different oil compositions.
With the temperatures being so low the gases are able to photochemically synthesize into long-chains of hydrocarbons which provide a steady rain upon the surface.