within 50 million years — a short time compared to the age of the Solar System. This suggests that methane must be somehow replenished by a reservoir on or within Titan itself. Most of the methane on Titan is in the atmosphere. Methane is transported through the cold trap at the tropopause. Therefore the circulation of methane in the atmosphere influences the radiation balance and chemistry of other layers in the atmosphere. If there is a reservoir of methane on Titan, the cycle would only be stable over geologic timescales. Evidence that Titan's atmosphere contains over a thousand times more methane than carbon monoxide would appear to rule out significant contributions from cometary impacts, because comets are composed of more carbon monoxide than methane. That Titan might have accreted an atmosphere from the early Saturnian nebula at the time of formation also seems unlikely; in such a case, it ought to have atmospheric abundances similar to the solar nebula, including hydrogen and neon. Many astronomers have suggested that the ultimate origin for the methane in Titan's atmosphere is from within Titan itself, released via eruptions from cryovolcanoes. Another possible source for methane replenishment in Titan's atmosphere is methane clathrates. Clathrates are compounds in which an ice lattice surrounds a gas particle, much like a cage. In this case, methane gas is surrounded by a water crystal cage. These methane clathrates could be present underneath Titan's icy surface, having formed much earlier in Titan's history. Through the dissociation of methane clathrates, methane could be outgassed into the atmosphere, replenishing the supply. On December 1, 2022, astronomers reported viewing clouds, likely made of methane, moving across Titan, using the James Webb Space Telescope. Daytime and Twilight (sunrise/sunset) Skies Sky brightness and viewing conditions are expected to be quite different from Earth and Mars due to Titan's farther distance from the Sun (~10 AU) and complex haze layers in its atmosphere. The sky brightness model videos show what a typical sunny day may look like standing on the surface of Titan based on radiative transfer models. For astronauts who see with visible light, the daytime sky has a distinctly dark orange color and appears uniform in all directions due to significant Mie scattering from the many high-altitude haze layers. The daytime sky is calculated to be ~100-1000 times dimmer than an afternoon on Earth, which is similar to the viewing conditions of a