第1页第2页第3页 earth moon 第4页 spaceship astronaut 第5页 space travel 第6页 Scientists have sent spaceship to Mars. The journey has taken several months. 第7页 Astronauts have already been to the moon. 第8页 No one has been to Mars yet, because Mars is very far away, much farther than the moon. 第9页 Lots of scientists are working hard in order to send astronauts to Mars one day. 第 10 页 Scientists think that there has been life on the Earth for hundreds of millions of years. However, we have not found life on any other plants yet .
