age, composition, orbital distance, and stellar type, not just mass and composition.

Unlike a star, EGP atmospheric temperatures are sufficiently low that chemistry is destiny. This is a distinguishing characteristic of substellar-mass objects (SMOs). The atmosphere of a gaseous giant planet is the thin outer skin of molecules that regulates its emission spectrum and cooling rate. Molecular hydrogen (H$_2$) is the overwhelming constituent, followed by atomic helium. An EGP’s effective temperature (, the temperature of its “photosphere") can vary from $\sim$1500 K for the more massive EGPs at birth to $\sim$50 K for the least massive EGPs after a Hubble time. This wide range translates into a rich variety of atmospheric constituents that for a given mass and elemental composition evolves significantly. At birth, Jupiter had a  near 600-1000 K and the appearance of a T dwarf[@burgasser] brown dwarf. It had no ammonia or water clouds and, due to the presence of atomic sodium in its hot atmosphere, had a magenta color in the optical[@bur.rmp]. Its atmosphere was depleted of aluminum, silicon, iron, calcium, and magnesium due to the formation and settling to depth of the refractory silicates (“dirt") that condense in the temperaure range $\sim$1700-2500 K[@BurrowsSharp99; @Lodders99; @Lodders02]. Water 