About our atmosphere.

Recently, we took a closer look at the water on the rather smooth sphere we live on. But how about our atmosphere – this thin layer of gasses surrounding the earth, kept in place by gravity? When you reach cruising altitude in a modern jet plane you have about 2/3 of the mass of the earth’s atmosphere beneath you. The troposphere reaches up to an altitude of 16 km in tropical areas but only up to about 10 km closer to the poles and it contains 75% of the total mass of our atmosphere. Look at a desk globe with a diameter of 30 cm. In scale, the troposphere would reach out about 0,3 mm from the surface of the globe. Nevertheless, it contains all the aerosols and all the water in our atmosphere.

Between earth's surface and the Hubble telescope. Credit: NASA
From the surface of the earth up to the altitude of the Hubble telescope. Please note the auroras and its colors. Credit: NASA

It is not to be taken for granted that a planet has an atmosphere. Due to the Earth’s gravity and to its magnetic field our atmosphere isn’t totally blown away by the solar wind. We have to remember that the sun is, in fact, a fusion reactor out of control. And at a distance of 150 million kilometers we just have to accept the sun’s radiation. It is not completely harmless. The UV-radiation is needed by us humans in a certain amount to start the production of vitamin D in our skin. Too much could lead to burned skin and – in a worst case – skin cancer.

The stratospheric ozone layer acts like a protective blanket in the atmosphere, shielding life on Earth from harmful ultraviolet radiation emitted by the Sun. In the 80s, it was discovered that the ozone layer was extremely thin over the polar areas. The ozone hole was quite frequently talked about during debates about our environment. It was discovered that long-lived manmade chemicals, chlorofluorocarbons (CFCs) circulated into the stratosphere. They broke down and produced highly reactive chlorine atoms. Each chlorine atom can break apart more than one hundred ozone molecules. The stratospheric ozone layer was rapidly thinned out and its ability to block out UV rays was decreased. Today, due to the Montreal protocol made 1987, the situation is much better than anyone thought back in the eighties. Nowadays the ozone layer is watched continuously by satellites.

A meteor photographed burning up in the atmosphere in August 2011 by an astronaut aboard the ISS. Cerdit: ESA
A meteor photographed burning up in the atmosphere in August 2011 by an astronaut aboard the ISS. Credit: ESA

Every day some 100 000 kg of meteoroids, micrometeoroids and space dust burns in our atmosphere. Look up to the night sky and, statistically, you should see several fireballs in the sky each hour. During a meteor shower, it’s just seconds between these so called “shooting stars”.

When you see a meteor, completely burned up in the sky, it’s most likely to happen in the Mesosphere. More than 100 km above the surface of the Earth there are not enough molecules in the atmosphere to create the friction with the meteoroid to cause the heat needed. June 28, 2015, a cargo ship was launched to carry supplies to the International SpaceStation. Unfortunately, the cargo ship was lost. Among other scientific articles onboard was equipment meant to perform the first space-based observations in HD of meteors entering the Earth’s atmosphere.

Think about it for a while. This thin layer of gasses we call our atmosphere is protected by the Earth’s magnetic field and protects the Earth from meteorites crashing into its surface. When you see a fireball in the sky it’s no more than 100 km above Earth’s surface. Compared to the desk globe mentioned earlier it would be some 2 mm from the surface.

Thanks to Ken Zetie


JanJan teaches mathematics and interdisciplinary science to pupils 13-16 years of age at Sursik School, Pedersöre, Finland. Space-related science often gives some sort of answer to the question “Why?”, a question quite common in math class. It also triggers curiosity, one key component in progress.

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