1. Of all the planets in our own solar system, we are now pretty certain the Earth is the only one on which life can survive.
    我们目前可以肯定的是，在我们太阳系的所有行星中，地球是生命能存在的唯一行星。

2. It is the one world in the Solar System that is most like the Earth.
    火星是太阳系里与地球最接近的一颗行星。

3. In our own solar system, for example, Venus is far too hot and Mars is far too cold to support life.
    举例来说，在我们的太阳系里，对于生命来说，金星的温度太高，而火星的温度则太低。