Điền từ thích hợp vào mỗi chỗ trống

 surface     survive      frozen       universe     explore      missions        down      might

          As we explore the (1) ___________, we naturally ask, “Is there life on other planets?” In 1976, NASA’s twin Viking landers touched (2) ___________ on Mars in an attempt to answer a weighty question: Is there life on the Red Planet? Since then, NASA and other space agencies have sent many more (3) ___________ to Mars. However; the answer so far is, “We don’t know, but we’ll keep searching.” All life on Earth needs liquid water to (4) ___________. Since spacecraft haven’t found any liquid water on Mars’ (5) ___________, scientists think that there is no life there. But what about below the surface? Spacecraft have discovered (6) ___________ water in Mars’ polar ice caps and in clouds of ice crystals. This means that there (7) ___________ be liquid water below the surface where it’s warmer. NASA plans to continue to (8) ___________ Mars every two years. In future missions, we’ll explore below the surface and search for liquid water - and life!