Daily Celestial Challenge: Thursday-ForcesinNature

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Polar stratospheric clouds, or PSCs, are formed in the stratosphere at high altitudes, between 15 and 25 kilometers (approximately 50,000 to 80,000 feet). PSCs only form in very cold temperatures, approximately -78 ° C (-108 ° F). Sometimes, during the winter near the north and south poles, temperatures in the lower part of the lower stratosphere can become quite cold. That is when the PSC can be formed.

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There is a lot of water vapor in the air of the troposphere. It is for this reason that we have a large amount of clouds in the troposphere. The clouds are made of tiny droplets of water, or small crystals of water ice. On the other hand, the stratosphere above us is very, very dry. In the stratosphere it is rare that there are clouds. Some PSCs are composed of water ice crystals. Other PSCs contain nitric acid and sulfuric acid!

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Note: @sirknight started a contest and its daily theme's are:
Sunday-Light
Monday-Darkness
Tuesday-AnimalKingdom
Wednesday-Structures
Thursday-ForcesinNature
Friday-LoveBeautyFreedom
Saturday-Agriculture