Extraterrestrial atmosphere reaching 70 m/s or more in the upper troposphere. The stratosphere and mesosphere extend from 65 km to 95 km in height. The thermosphere and exosphere begin at around 95 kilometres, eventually reaching the limit of the atmosphere at about 220 to 250 km. The air pressure at Venus' surface is about 92 times that of the Earth. The enormous amount of CO in the atmosphere creates a strong greenhouse effect, raising the surface temperature to around 470 °C, hotter than that of any other planet in the Solar System. The Martian atmosphere is very thin and composed mainly of
A Town Called Mercy called the Gunslinger. However, the Gunslinger is a product of experiments by Jex to win a civil war on his planet, and the Doctor is unsure of what is the right thing to do. Showrunner Steven Moffat pitched the Wild West theme to Whithouse when thinking of ways to give each episode a distinct theme. Whithouse further developed the theme, including classic Western tropes and a sympathetic villain. "A Town Called Mercy" and the previous episode "Dinosaurs on a Spaceship" were the first to enter production for the seventh series. Much of the episode was filmed in March 2012 in