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cheap amaryl Air grows colder and thinner with altitude. Yet there's a point in Earth's atmosphere at about 40,000 to 50,000 feet where the air stops cooling and instead begins to warm again. This invisible turnaround is known as a tropopause, and it's not only existent in our own atmosphere. In the 1980s, NASA discovered tropopauses in the atmospheres of the planets Jupiter, Saturn, Uranus and Neptune along with Saturn's largest moon, Titan. All of these turnaround points occurred at roughly the same level in the atmosphere of each of these different worlds at a pressure of about .1 bar--one-tenth of the air pressure at Earth's surface.