作者：Amanda Restrepo Kerguelen 4 年以前
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The Solar System is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, the dwarf planets, and small Solar System bodies.
Mercury is the smallest, only a little bit larger than Earth's moon. Mercury has no moon.
It experiences dramatic changes in its day and night temperatures: Day temperatures can reach a scorching 840 F (450 C), which is hot enough to melt lead. Meanwhile, on the night side, temperatures drop to minus 290 F (minus 180 C).
It also has a very thin atmosphere of oxygen, sodium, hydrogen, helium, and potassium and can't break-up incoming meteors, so its surface is pockmarked with craters, just like the moon.
