Earth batteries tap electric currents in the earth called telluric current. Including minor processes, there are at least 32 different mechanisms which cause telluric currents. Astronomers use Zeta Aquilae as a telluric standard star. It is possible to correct for the effects of telluric contamination in an astronomical spectrum. Earth batteries are sometimes referred to as telluric power sources and telluric generators. Water vapor and oxygen are two of the more important molecules in telluric contamination. There are two types of telluric iron. The Inuit were the only people to make practical use of telluric iron. Telluric currents flow in Earth and the oceans. Telluric acid and its salts mostly contain hexacoordinate tellurium. Telluric currents flow in the surface layers of the earth. The extremely rare telluric iron has been studied ever since. In April and May 2016 Vera Blue supported Matt Corby on his "Telluric" tour. Telluric currents are phenomena observed in the Earth's crust and mantle. "Telluric" was released on 11 March 2016.