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...slabs of frozen carbon dioxide scooting downhill. Some gullies start near the tops of sand dunes where an underground reservoir of water is very improbable. In 2008 the lander Phoenix actually saw water on Mars. When it scraped away at the dirt, it found water-ice a few centimetres down, but more excitingly droplets that could hardly be anything other than water were seen to form on the lander’s legs. It was suggested that ......

...cast irons can be treated, but should have a carbon content below 0.4% (and preferably below 0.25%) to produce a tough core. Process sometimes produces an over-high carbon content in the case profile, therefore a repeated carburise-diffuse sequence is adopted, relative process times are shown below. This is also used for producing deep cases. The shorter carburising times...