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题目内容
题目材料：
Since Earth is the only habitable planet known to humankind, the orbital and physical characteristics of Earth are used to define a habitable planet. In other words, habitability is the characteristic of an environment which has similar properties as those of Earth, and the capability of developing and sustaining Earthly life.
The statement above implies that the fact that the only habitable planet we know is Earth has strongly biased our understanding of the conditions required for life. From the astronomers' point of view, and owing to the essential role that water plays on life on Earth, the definition of a habitable planet is tied to the presence of liquid water. However, as simple as this definition might be, it has strong connections to a variety of complex interdependent processes that need to be unraveled and understood to make predictions on which planets could be habitable. The basic principle is that the surface temperature and pressure of a planet should allow for liquid water. This is determined by the amount of irradiation that the planet receives from the star, and the response of the planet's atmosphere. The latter delicately depends on the composition of the planet, and that in turn determines the heat transport mechanism, cloud presence, and many other atmospheric properties
The irradiation from the star is contingent on the type of the star and the planet's orbital parameters. The atmospheric composition, on the other hand, depends on the in-gassing, out-gassing, ad escape histories of the planet. The in-gassing and out-gassing accounts are intrinsically connected to the interior dynamics of the planet, while atmospheric escape is related to a variety of thermal and non-thermal processes, which themselves are linked to the presence of a magnetic field. It is not clear how delicate the balance between these different processes could be. Nor is it evident if there are different pathways that could yield a habitable planet. However, the fact that Earth has succeeded in developing life indicates that our planet might have followed one, perhaps of many evolutionary paths that resulted naturally in a complex system by the series of steps and bifurcations that it encountered. It is important to note that the complexity and interdependence of these processes cannot be taken as evidence for the uniqueness of life on Earth. The road ahead is to understand which planetary characteristics are indispensable, which are facilitating, and which are a byproduct of evolution. For that purpose, and in order to assess the possibility that a planet (e.g, a super-Earth) may be habitable, a deep understanding of these processes (i.e, interior composition and dynamics, planet's magnetic field, and atmospheric characteristics) is required.
The statement above implies that the fact that the only habitable planet we know is Earth has strongly biased our understanding of the conditions required for life. From the astronomers' point of view, and owing to the essential role that water plays on life on Earth, the definition of a habitable planet is tied to the presence of liquid water. However, as simple as this definition might be, it has strong connections to a variety of complex interdependent processes that need to be unraveled and understood to make predictions on which planets could be habitable. The basic principle is that the surface temperature and pressure of a planet should allow for liquid water. This is determined by the amount of irradiation that the planet receives from the star, and the response of the planet's atmosphere. The latter delicately depends on the composition of the planet, and that in turn determines the heat transport mechanism, cloud presence, and many other atmospheric properties
The irradiation from the star is contingent on the type of the star and the planet's orbital parameters. The atmospheric composition, on the other hand, depends on the in-gassing, out-gassing, ad escape histories of the planet. The in-gassing and out-gassing accounts are intrinsically connected to the interior dynamics of the planet, while atmospheric escape is related to a variety of thermal and non-thermal processes, which themselves are linked to the presence of a magnetic field. It is not clear how delicate the balance between these different processes could be. Nor is it evident if there are different pathways that could yield a habitable planet. However, the fact that Earth has succeeded in developing life indicates that our planet might have followed one, perhaps of many evolutionary paths that resulted naturally in a complex system by the series of steps and bifurcations that it encountered. It is important to note that the complexity and interdependence of these processes cannot be taken as evidence for the uniqueness of life on Earth. The road ahead is to understand which planetary characteristics are indispensable, which are facilitating, and which are a byproduct of evolution. For that purpose, and in order to assess the possibility that a planet (e.g, a super-Earth) may be habitable, a deep understanding of these processes (i.e, interior composition and dynamics, planet's magnetic field, and atmospheric characteristics) is required.
以上解析由 考满分老师提供。
