Mercury is the smallest and closet planet to the sun. It has the same size as the Moon and its diameter is 1.4 times that of the Moon. Mercury's surface exhibits enormous escarpments of huge length difference and we call them wrinkle ridge. This is the unique geological feature of Mercury and they may be caused by the contraction after cooling down.

Mercury is small in size but was cooled down in a short time. Along with the rapidly dropping temperature, Mercury's surface contracted vigorously and that caused wrinkles.

Mercury's surface has many similarities with that of the Moon and we can see meteorite bombardments. There is no ocean and atmosphere surrounding. It is quite desolate.

The average density of Mercury is 5430 kilograms per cubic kilometer and it is just next to that of Earth among nine planets. Scientists conclude that it is because Mercury has a large iron core.

Mercury is close to the Sun and the tropic region on it is very hot due to strong sunray. Two poles only receive weak sunlight; thus, some bottoms of meteorite bombardments never receive sunlight and become "Dark Area" with the temperature of -210C. Thus, glacier can last in this area for more than billions years.

There is no air on Mercury and there is no ocean to adjust the temperature. Mercury has the extreme type of continent climate with huge temperature difference during day time and night time up to 600。C, ranking the first in the Solar system.