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  • Elizabeth Cocking

Did you know?The Earth’s atmosphere

This Month . . . The Earth’s atmosphere. We may take it for granted but without it we would not exist.

The Earth’s atmosphere consists of five layers. From the lowest to the highest, they are the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The exosphere extends to around 10,000 km above the Earth, where it finally gives way to the solar wind.

The thermosphere extends approximately 85 km to 500 km above Earth and is home to the International Space Station in Low Earth Orbit. This is also where the Northern and Southern Lights auroral displays occur.

As you go higher the air pressure gets lower and so do boiling points. At the top of Mount Everest, approximately 9,000 m above sea level, water boils at 72°C. However, if you ascend to around 18,000 metres, the air pressure drops to a level that’s deadly without a pressurised suit.

Our atmosphere serves as a protective blanket safeguarding us from lethal solar radiation, extreme temperatures and impact events. Earth’s atmosphere burns up almost all the meteorites and space junk that encounter it. However, there are some objects that are too large or moving too fast for the atmosphere to burn up before they hit the surface, as the dinosaurs found out 65 million years ago!

The atmosphere is home to an average of almost 150 trillion litres of water at any one time, which is enough to drown the entire planet in 2.5cm of rainwater. However, while it sounds like a lot, atmospheric water vapour only accounts for 0.001% of all the water on Earth.

Image::Sunset on the Indian Ocean as seen by astronauts aboard the International Space Station (ISS). The image presents an edge-on, or limb view, of Earth’s atmosphere as seen from orbit. Earth’s curvature is visible along the horizon line, or limb, that extends across the image from center left to lower right. Above the darkened surface of Earth, a brilliant sequence of colors roughly denotes several layers of the atmosphere. Credit: NASA



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