— _________.

    Is there life on other planets? There are seven other planets in our {#blank#}1{#/blank#} system, but {#blank#}2{#/blank#} of them has an environment like that of the {#blank#}3{#/blank#}. Spaceships   from the earth have done surveys of the other planets, but they have not found any life there. Why has no one from other planets tried to {#blank#}4{#/blank#} with us? It is true that scientists have not discovered life on other planets in the {#blank#}5{#/blank#} yet, but some scientists believe that they will find it some day.