The planet Mars is the closest and most similar planet to Earth. It is very{#blank#}1{#/blank#}to scientists. For example, Mars has seasons with{#blank#}2{#/blank#}weather, but other planets have the same temperatures all year round. Was there{#blank#}3{#/blank#}on Mars?

    To find out, scientists need{#blank#}4{#/blank#}if Mars ever had water. In 2004. two robot explores (探测器), or 'rovers', called Spirit and Opportunity were sent to look for{#blank#}5{#/blank#}of water. These rovers can drive over rocks{#blank#}6{#/blank#}all kind of rough ground. They can also use cameras and send photos{#blank#}7{#/blank#} to Earth. First, the two rovers found chemicals and patterns (图文) in the rocks that were probably made by water. Then, they moved to another area and{#blank#}8{#/blank#}other rocks which may have been created by water. Now scientists think there was probably water on the planet long ago. Today  {#blank#}9{#/blank#}are still not sure if there was life on the mars. They{#blank#}10{#/blank#}need more information to decide. The discoveries of the two rovers answered some old questions, but they also brought up many new ones.