The answer may be that virtually all the water on Mars is now locked in the permafrost layer under the surface, with more contained in the planet's polarcaps.
It is this irreversibly modified world, from the polarcaps to the equatorial forests, that is all the nature we have.
从极地盖帽到赤道森林，这是不可逆转的世界，这就是我们拥有的所有自然。
3
Both planets have roughly the same amount of land surface area, sustained polarcaps, and both have a similar tilt in their rotational axes, affording each of them strong seasonal variability.