地球之外的冰雪世界――行星冰冻圈研究综述

Ice World Beyond Earth—Brief Introduction to Planetary Cryosphere

文章介绍了太阳系和太阳系外行星冰冻圈。太阳系各行星和卫星的表面温度差异很大,它们的冰冻圈发育各不相同。水星和月球的两极陨石坑的永久阴影区中可能有水冰存在。金星太热,表面既没有液态水,也不可能有水冰存在。火星两极存在永久性冰帽,包括水冰和干冰(固态CO2)。在太阳系雪线之外,存在很多冰卫星和富含水的矮行星,它们的主要是由水冰组成的;在极低的温度下,水冰甚至比地球上的岩石还要坚硬,并成为这些星体的壳层。除了水冰,其他易挥发组分如CO2、CH4、N2、CO等在极低温度下都会凝固为冰,形成不同于水冰的冰冻圈。因此,行星冰冻圈具有与地球冰冻圈迥然不同的丰富多样性。对行星冰冻圈的研究有助于我们扩大视野,更深入地理解地球冰冻圈,也将有助于我们理解太阳系的形成、地球水分的来源、地球深时古气候环境和生命演化,以及开展未来的系外生命探测。

In the present paper,we briefly introduce the planetary cryosphere of solar planets and exoplanets.Planets and satellites in the solar system have very different surface temperatures.Therefore,they have very different cryosphere.Mercury and the Moon likely have water ice in the permanent dark areas of craters in polar regions.Venus is too hot to have a cryosphere.Mars has permanent polar ice caps that include both water ice and carbon-dioxide dry ice.Beyond the snowline of the solar system,there are many dwarf planets and satellites that are mainly consisted of water ice.With extremely low temperatures,water ice becomes even harder than the rocks on Earth and is actually the shell layer of these satellites and dwarf planets.In addition to water ice,other gases over Earth,such as CO2,CH4,N2,CO,and so on,are condensed to solid states under conditions of extremely low temperatures.They form different cryosphere from water ice.Therefore,planetary cryosphere is very different from that on Earth,and they have plenty divergences.Studies on planetary cryosphere would largely broaden our understanding on Earth’s cryosphere and benefit our understanding of the formation of the solar system,origin of water on Earth,evolution of life and climate environment on Earth,and extra-solar life detection in future.