• Question: why is planet earth the only planet that provides enough oxygen to live on and why don't any of the other planets provide enough oxygen?

    Asked by x-x-LILSKI-x-x to Alison, Hannah, Jonny, MarthaNari, Paul on 18 Jun 2015.
    • Photo: Paul Brack

      Paul Brack answered on 18 Jun 2015:

      Scientists believe that the Earth was formed about 4.5 billion years ago. Its early atmosphere was probably formed from the gases given out by volcanoes. It is believed that there was intense volcanic activity for the first billion years of the Earth’s existence. Gases like carbon dioxide, hydrogen sulphide and methane were around in large quantities, and there was pretty much no oxygen. It is thought that the atmospheres of Mars and Venus today, which contain mostly carbon dioxide, are similar to the early atmosphere of the Earth.

      However, the big change on earth came when 2.7 billion years ago, bluish-green microscopic organisms called cyanobacteria began to flourish in the oceans. They made oxygen from carbon dioxide, water, and sunlight—the process called photosynthesis. This meant that we gradually got more and more oxygen in our atmosphere, unlike the other planets.

      So it’s all down to the cyanobacteria!

      There’s much more detail on the website where I got most of this from http://forces.si.edu/atmosphere/02_02_00.html and also a bit more at http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/oils/changesrev7.shtml

    • Photo: Jonny Brooks-Bartlett

      Jonny Brooks-Bartlett answered on 19 Jun 2015:

      I would also add that it’s very likely that other planets in the universe have similar amounts of oxygen but they are just really far away. So Earth may not be the only one and there may be life elsewhere in the universe.

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