Titan tholins are nitrogen-rich organic substances produced by the irradiation of the gaseous mixtures of nitrogen and methane found in the atmosphere and surface of Titan. Titan's atmosphere is about 97% nitrogen, 2.7±0.1% methane and the remaining trace amounts of other gases. In the case of Titan, the haze and orange-red color of its atmosphere are both thought to be caused by the presence of tholins.