The Atmosphere: An Introduction

The atmosphere is the gaseous blanket surrounding the entire planet. The word atmosphere is derived from the Greek word Atmo meaning air. 

Pie chart showing the chemical composition of the atmosphere.
Credits: Patti Isaacs Management and Production

As the pie chart above illustrates, oxygen is the second most abundant gas in our atmosphere. Oxygen is vital for life on planet Earth; all living organisms require this gas for aerobic respiration in order produce the energy required for metabolic reactions. 0.17% of the atmosphere consists of other gases including neon, helium, methane, krypton, hydrogen, nitrous oxide, xenon, ozone, iodine, carbon monoxide and ammonia. Water vapour is also present at low altitudes in the troposphere. The stratosphere, which is the layer above the troposphere, contains a layer of ozone gas. The ozone layer is responsible for filtering high energy ultraviolet (UV) rays which have enough energy to damage the DNA inside cells. This is why exposure to high levels of UV radiation can cause skin cancer. 

Aerobic respiration

The atmosphere is also a shield against meteoroids which are the solid debris any comets or asteroids leave in their path whilst travelling through space. Meteoroids travel at high speeds of up to 70 kilometres per second. Upon entering the Earth's upper atmosphere, the mesosphere, a meteoroid is forced to slow down as the molecules of atmospheric gases provide the drag force friction. The friction has a heating effect and causes the meteoroid to ignite; it is now formally known as a meteor.

This time-lapse photograph shows a meteor shower. A meteor shower occurs when the Earth passes through a belt of debris from a passing comet or asteroid. As a result, many meteors (also known as shooting stars) can be seen in the sky. 
Credits: Kenneth Brandon

Our atmosphere is responsible for the weather we experience on Earth. Different areas of the globe experience different weather patterns which are essentially driven by energy from the sun. Weather is caused by movement of air masses; warm air is carried from the equator to the poles. Areas of mid-high latitudes such as the United Kingdom can experience both cool air from the Arctic and warm air from the equator. Also, it is due to the wind plants were able to colonise land and evolve; wind is responsible for the transportation of seeds and minerals across great distances. Today, wind carries sand and minerals for fertilisation from the Sahara to the Amazon rainforest across the Pacific Ocean.

Air masses moving towards the British Isles. 
Credits: Met Office