Biology Forums - Study Force

Although it currently does not have an ocean, ____ is thought to have had one in the distant past.
  a. Europa
  b. Saturn
  c. Jupiter
  d. Mars

ANS: D
Mars shows signs there might have been an ocean on its surface. It is possible this ocean occupied low
areas of the planet's northern hemisphere. This would have existed as much as 3.2 billion years ago
when conditions were warmer. The red planet might have even had as much carbon dioxide in its
atmosphere as early Earth. Information can be found in the section Are There Other Ocean Worlds.