Air: The Gas Around Us

It is not possible to see it, smell it, taste it or touch it, nevertheless it is constantly around us and we could not survive without it. We are talking about the gas around us called air. We breathe in at least 6 m₃ per day without even thinking about the importance of air. A human can survive three weeks without food and three days without water, but only three minutes without breathing. Moreover, life on our planet would have never developed without this gaseous envelope.

What is Air Composed Of?

In ancient times, air was believed to be a homogeneous element. Today, we know that it is composed of different gases. Nitrogen is the major component, making up 78 percent of the volume, which amounts to almost four fifths. The oxygen necessary for our survival makes up 21 Vol%, that is, about one fifths. The remaining percent is shared between several other components. The biggest part of this is the noble gas argon.

The table shows the composition of natural, dry air.

Additionally, "normal" air contains a variable fraction of water vapour between 1 and 5 Vol% depending on temperature and atmospheric pressure, other trace gases (e.g. exhaust gases) and suspended matter. Because of human emissions, the amounts of carbon dioxide, methane and laughing gas has gradually increased.

Could We Survive in a Differently Composed Atmosphere?

A human being needs an atmosphere with enough oxygen and no poisonous gases for survival. Otherwise, the conditions do not have to be the same. For example, the air an astronaut breathes in the Apollo spaceship contains a much higher oxygen amount with only a third of the normal atmospheric pressure.

What About Other Planets?

No other planet in our solar system possesses an atmosphere we could survive in, not to mention too high or too low temperatures and the lack of water.

Mercury has no atmosphere at all. The atmospheric pressure on Venus is ninety times higher than on Earth and the atmosphere consists mainly of carbon dioxide. The atmosphere on Mars contains some oxygen in addition to carbon dioxide, but is way too thin for us. The atmospheres of the big gas planets Jupiter, Saturn, Uranus and Neptune are extremely hostile, since they are composed of the toxic gases ammonia and methane.