In this image, the Sun is below the horizon and casts a red-orange glow on the Earth’s surface, which is the troposphere – the lowest layer of the atmosphere. The tropopause is the brown line along the upper edge of the troposphere. Up there is the stratosphere, the dark part and the upper atmosphere.
A peculiarity of the atmospheres of Earth, Jupiter, Saturn, Uranus and Neptune is that there may be billions of planets. University of Washington astronomers say the discovery could aid in the search for places where life exists.
At first we knew the air was colder and thinner the higher we climbed, but in 1902, scientist Leon Teisserenc de Bort, armed with levitation instruments, noticed a point in the Earth’s atmosphere at around 40,000 to 50,000 feet where the air stopped cooling and began to warm.
He called this completely amorphous change the “tropopause” (the top region of the troposphere) and coined the terms “stratospheric” for the atmosphere above and “troposphere” for the lower layer.
Then, in 1980, NASA spacecraft discovered tropopauses which are also present in the atmospheres of Jupiter, Saturn, Uranus and Neptune, as well as Saturn’s largest moon, Titan. More importantly, these “turning points” occur in the same atmosphere of each of the different planets – at about 0.1 bar, (1/10th the atmospheric pressure at Earth’s surface).
Now, UW astronomers Tyler Robinson and David have used physics to simulate why this is happening and show that tropopauses are likely present in the galaxy’s billions of planets and satellites.
The explanation lies in the physics of infrared radiation. Atmospheric gases gain energy by absorbing infrared light from the illuminating side of a rocky planet or from deeper parts of the atmosphere of a planet like Jupiter.
Using an analytical model, Catling, a professor of earth and space sciences, and Robinson, a senior research fellow in astronomy, showed that at an altitude, the atmosphere becomes transparent due to low pressure. Above a pressure of 0.1 bar, this absorption is visible. Ultraviolet light, the light that causes the atmospheres of giant planets like Earth and Titan, gets hotter as they rise. Astronomers are also using this discovery to extrapolate temperature and pressure conditions on the planet’s surface and find out if there is life elsewhere.
Apparently, popular physics not only explains what happens in the atmosphere of the solar system, but can also help us search for life elsewhere.