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Asked by Gracie to Sean, Michel, Kevin, Chloe, Anthea on 17 Nov 2014.
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Sean Kelly answered on 17 Nov 2014:
Hi Gracie.
Good question! I’m not an expert but I’ll do my best to answer. There actually is oxygen in space and in the weak atmosphere of the moon but only in tiny, tiny amounts – not enough for us to survive. On earth we have a lot of oxygen in the air and we need this to survive. The reason oxygen and other elements of our atmosphere stay close to earth is that gravity keeps pulling on them to keep them close. The moon and lots of other planets only have very weak gravity which means the oxygen can escape out into space. And space is so huge and so vast that the elements such as oxygen are really spread out! The result is that oxygen is so spread out and diluted into the vastness of space that we couldn’t breath in it and survive. Of course there are also other reasons we can’t survive in space such as the intense radiation from the sun! I hope that helps
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Kevin Healy answered on 21 Nov 2014:
The question really is why is there so much oxygen on earth in comparison to all the other planets and moons. The answer is thsat it hasnt alway been like this. Two billion years ago there wasnt much oxygen on earth either it would be more similar to venus then to the earth today with lots of pisonous gasses like Carbon dioxide (CO2). Soem bacteria however love CO2 and use along with light to make energy through photosynthesis. When the ability to first do this on earth evolved it meant that whole planet was coverd in green bacteria. Unlike us the by product of this form of energy is oxygen so after millions of years all these bacteria converted nearly all the CO2 in the atmosphere into Oxygen. This is great for us as we breath in Oxygen but breath out CO2. This has kept the earth atmosphere in balance for well over a billion years!
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