We show that for a field k, algebraic over ℚ, and F a field of characteristic zero, the triangular spectra of mixed Tate motives (resp. mixed Artin-Tate motives), denoted by DMT(k)F (resp. DMAT(k)F), are both isomorphic to spec(F). We further compute the Picard groups of DMT(k)F and DMAT(k)ℚ.