Astronomers Think That Most Comets Come from the Oort Cloud

Q50: _ is the smallest of the inner

Q51: The surface of Venus is hidden by

Q52: Martian winds have created _.<br>A) polar ice

Q53: Of all the planets in the solar

Q54: When 17^th century astronomer _ first viewed

Q55: The nucleus of a comet is a

Q57: The four planets nearest the sun are

Q58: Our galaxy is called the _.<br>A) Oort

Q59: All the planets are exactly the same

Q60: To the best of our knowledge, the