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 solid carbon dioxide.

若冰层上方还存在一层固态气体层，如干冰——二氧化碳的固态形式，维持液态水存在的冰层厚度要求就能相对降低。

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Spring has sprung on Mars, bring with itthe disappearance of carbon dioxide ice (dry ice) that covers the northpolar sand dunes.

春天在火星上跃动，覆盖在北极沙丘上的二氧化碳干冰消失了。

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An annual winter chills the southern hemisphere, creating around the pole a frost composed in large part of frozen carbon dioxide, or dry ice.

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The Federation Aviation Authority limits how much dry ice can be on a plane because it releases carbon dioxide (too much can harm passengers and crew).

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