A thaw occurs each spring in the Northern Hemisphere of Mars, as the warming climate causes solidcarbondioxide ice to sublimate directly to vapor.
火星北半球每到春天来临都会发生一次解冻，温暖的气候造成了固态的二氧化碳冰直接升华成气体。
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The ice cap could be thinner and still protect water if it were topped with a layer of frozen atmospheric gas, such as dry ice, which is solidcarbondioxide.
Some companies have commercialized a process that captures carbondioxide and converts it to solid material, but those efforts rely on a chemical process to capture carbondioxide.