M级行星

M级行星又称类地行星， 是行星等级划分的。M 级行星出现在恒星的 "可居住区", 直径通常在 10,000~15,000 公里大气中含有氧及氮, 充满水及生物但若地表 97% 以上皆被水掩盖, 则归类为 N 级行星。典型的 M 行星包括地球，Cardassia and Vulcan。

英文原文：

Class M (Terrestrial):

Class M planets are found in a star's "habitable zone" and are usually

between 10,000 and 15,000 kilometers in diameter. Their atmospheres contain

oxygen and nitrogen. Water and life-forms are abundant. If over 97% of the

surface is covered by water, then the planet is designated a Class N planet.

Examples of Class M planets include Earth, Cardassia and Vulcan.