[inquest]

I've never heard that Terra, Luna, and Sol are any more "proper" than earth, moon, and sun. The words mean the exact same thing, just in different languages.

[PatrickHenry]

I've never heard that Terra, Luna, and Sol are any more "proper" than earth, moon, and sun. The words mean the exact same thing, just in different languages.

Depends on context. If a hole is being dug in the earth (refering only to the ground), I wouldn't capitalize it. If I'm refering to the orbit of the Earth (name of the planet), I would. But I'm not the final authority in such matters. Your editor will enforce his own rules.