Across
- 1. The earth, Mars, Jupiter, and so on
- 5. It is xxx to imagine how large the universe is.
- 8. No one has xxx with us out of the earth.
- 9. It takes a long time for the spaceships to xxx other planets.
Down
- 2. The earth has a suitable xxx for life to survive.
- 3. Also called Milky Way
- 4. the past participle （过去分词）of "find"
- 6. Eight planets go xxx the sun in the solar system.
- 7. to find out about sth.