Scientists think that there has been life on Earth for 小题1: (百万) of years. However, we haven’t found life on other 小题2: (行星) yet. The earth, the moon, and the sun are a small part of our galaxy. Scientists have 小题3: ( 发现) many other galaxies in the universe. And there are many books about the universe. I’ve just finished 小题4: (看) a great book at school. It is a book about the solar system. It is so good that I’ve 小题5: (已经) asked the library to keep the next book for 小题6: (我). In the book, it says that astronauts have 小题7: (去) to Mars and even to Jupiter. I’ve never read that before. I’ve 小题8: (写信) to NASA to ask them for 小题9: （更多）information about astronauts and space. I hope they will write 小题10: (回) soon.
