Listen and fill in the blanks.
Planets
There are eight planets in our ___________(1) system. ___________(2) of them are main planets. Pluto is not one of them. The planets ___________(3) the sun. Scientists ___________(4) the ___________(5) through a ___________(6) telescope, and they have many space ___________(7). For example, Mars ___________(8) Mission began in 2003. Mankind is trying to discover ___________(9) of water on the ___________(10) of Mars.