Mimas is the seventh of Saturn¹'s known satellites:

　　orbit:    185,520 km from Saturn

　　diameter: 392 km

　　mass:     3.80e19 kg

　　Mimas was one of the Titans slain² by Hercules.

　　Discovered in 1789 by Herschel.

　　Mimas' low density³ (1.17) indicates that it is composed mostly of water ice with only a small amount of rock.

　　The surface of Mimas is dominated by an impact crater⁴ 130 km across, known as Herschel; it's almost 1/3 of the diameter of the entire moon. Herschel's walls are approximately 5 km high, parts of its floor measure 10 km deep, and its central peak rises 6 km above the crater floor. The impact that made this crater must have nearly disrupted Mimas. Fractures can be seen on the opposite side of Mimas that may be due to the same impact.

　　The surface is saturated⁵ with impact craters⁶. But no others are nearly as large as Herschel. This suggests that early in its history, Mimas was probably impacted by even larger bodies than the one that created Herschel which completely disrupted the new moon (wiping out the evidence of earlier large impacts) but that the impact debris⁷ then coalesced⁸ again to form present-day Mimas.

　　Mimas 是土星已知卫星中距土星第七近的一颗：

　　公转轨道：距土星 185,520 千米

　　卫星直径：392 千米

　　质量：3.80e19 千克

　　Mimas是被赫拉克勒斯残杀的巨人之一。

　　它于1789年由赫歇耳发现。

　　土卫一的低密度(1.17)表明它主要由一部分岩石混合着冰水组成的。

　　土卫一的表面主要是一个直径130千米的环形山，取名为赫歇耳(Herschel)，它几乎是整个卫星直径的三分之一。赫歇耳的内壁大约有5千米高，部分底部深10千米，中央山峰在环形山中隆起6千米。造成形成这个环形山的撞击一定差点将土卫一撞碎。撞击的反面可看到裂缝，可能就是因为这次撞击。

　　表面的环形山处于饱和状，但没有一个同赫歇耳一样大。这表明在土卫一的早期历史中，可能被一个比创造出这个环形山的星体更大的物体撞击，使新卫星完全破裂（抹去当时所有表面撞击痕迹），但后来碎片又合并在一起组成了今天的土卫一。