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阅读：考了super Earth，其中有题很猥琐，问uranium和sxxxx（两种放射性元素）indicate了什么，选contribute to Earth's convection（确定），有一个迷惑选项是super earth含这些元素的proportion比地球高，是错的，因为原文是说总量比地球高，但concentration是similar的
On Earth, mantle convection is the engine of most geologic processes. Below the plates that make up the surface of Earth, the mantle churns as it transports its internal heat toward the surface and then sinks back after it cools, similar to the convection in a boiling pot of water. The heat is in part left over after the planet’s formation and in part comes from the decay of radioactive elements in the mantle. We expect rocky super-Earths to have a similar concentration of radioactive heat sources or at least of uranium and thorium, because these elements are uniformly distributed throughout the galaxy and also get easily incorporated into planets during formation. Hence, being bigger than our home planet and having, in absolute terms, more radioactive material, massive Earth analogues produce more internal heat, which would translate into a more vigorous mantle convection.
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发表于 2019-12-22 16:34:58
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