methane
Eris is made of rock and ice.
Eris is made mostly of ice.
Eris's moon Dysnomia, appears to be made of material similar to Eris and Eris appears almost grey.
There made of Rock and something else
That is not known. Eris is too far away for us to know anything about its internal structure.
If you mean a large trans-Neptunian object: dwarf planet 136199 Eris then you have made a mistake. The dwarf planet Eris is thought to be quite white.
Eris. (Pronounced like 'Air-iss')
Eris is believed to be made primarily of rock and ice. It is categorized as a dwarf planet and is located in the outer regions of our solar system, similar to Pluto. It is not a gas giant like Jupiter or Saturn.
it is mostly made up of rock
poopy! always is a primary source
As of 2021, no space crafts have visited Eris, the dwarf planet located in the outer solar system. Most of the information we have about Eris comes from observations made from telescopes here on Earth.
The atmosphere on Eris is composed mainly of nitrogen and methane. The extremely cold temperatures and distance from the sun result in a very thin and tenuous atmosphere.