Mars and Venus have no life and no oceans of liquid water on their surfaces.
| Planet | Carbon dioxide (%) | Nitrogen (%) | Oxygen (%) |
|---|---|---|---|
| Mars | 95 | 2.8 | 0.2 |
| Venus | 96.5 | 3.5 | 0 |
| Earth | 0.04 | 78 | 21 |
Which conclusion is best supported by this information?
Planets without life or oceans have kept atmospheres that are mainly carbon dioxide, which supports the idea that oceans and photosynthesis removed carbon dioxide from the Earth's atmosphere.
Carbon dioxide is removed from the atmosphere of any planet over time, even without oceans or life.
The Earth's early atmosphere cannot have been mainly carbon dioxide, because the Earth's atmosphere today is very different from those of Mars and Venus.
Most of the oxygen in the Earth's atmosphere came from volcanoes, because Mars has a small amount of oxygen but no life.
51 exam-style questions on OCR GCSE Chemistry 6.3 Interpreting and interacting with earth systems, covering 6.3.1 Formation and evolution of the atmosphere, 6.3.2 The greenhouse effect and climate change, 6.3.3 Sources and problems of atmospheric pollutants, and 6.3.4 Producing potable water. Each one has a worked solution and a mark scheme showing where the marks go.