VOA慢速英语:火星上真的有水吗?

steep – adj. dropping or falling sharply; extremely high

microbial – adj. of or relating to microbes or bacteria

cliff – n. a high, steep surface of rock, earth, or ice

degree – n. a form of measurement for the size of angles, the shape formed by two lines extending from the same point

slope – n. ground that slowly drops downward or upward; ground that slopes

volume – n. an amount of something

cryptic – adj. difficult to understand; having or seeming to have a hidden meaning