Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science. 2013 May 3;340(6132):577-81. doi: 10.1126/science.1232226.
The search for exoplanets includes the promise to eventually find and identify habitable worlds. The thousands of known exoplanets and planet candidates are extremely diverse in terms of their masses or sizes, orbits, and host star type. The diversity extends to new kinds of planets, which are very common yet have no solar system counterparts. Even with the requirement that a planet's surface temperature must be compatible with liquid water (because all life on Earth requires liquid water), a new emerging view is that planets very different from Earth may have the right conditions for life. The broadened possibilities will increase the future chances of discovering an inhabited world.
寻找系外行星包含了最终找到并识别可居住世界的承诺。数千颗已知的系外行星和行星候选体在质量或大小、轨道和宿主恒星类型方面具有极高的多样性。这种多样性还扩展到了新型行星，这些行星非常普遍，但在太阳系中却没有对应物。即使要求行星的表面温度必须与液态水兼容（因为地球上所有的生命都需要液态水），但一种新出现的观点认为，与地球非常不同的行星可能具备生命存在的适宜条件。这种可能性的扩大将增加未来发现宜居世界的机会。
