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Unformatted text preview: deuterium will not. This suggests that Venus once had more water than at present. ( 5 marks ) (b) One way that Earth may have escaped developing such a thick atmosphere of carbon-dioxide is that the large amount of liquid water on Earth absorbed much of the carbon-dioxide. ( 5 marks ) 3. (a) Images of dry river channels and eroded craters, along with chemical analysis of Martian rocks, all show that water once flowed on Mars. ( 5 marks ) (b) That period ended at least 2-3 billion years ago. ( 5 marks ) 4. (a) Occultation. ( 2 marks ) (b) Kepler-10b should be considered as a terrestrial planet. Its density is about 8.8 times that of water, meaning it must be made mostly of rock and metal, like Earth. ( 5 marks ) (c) Kepler-10b cannot support life. It orbits its host star at less than 4 per cent of Mercury’s distance from the sun, making the planet’s surface too hot to support life. ( 5 marks )...
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- Spring '11