Fill in the blanks with an appropriate verb form.

A spacecraft orbiting Mars …………1…………. (finds / found / has found) huge deposits of ice at the south pole of the planet. Scientists said that if the ice deposits ……….2…………. (are / were / have been) in liquid form, they would be more than enough to blanket the entire planet in water.

 The scientists …………..3…………… (use / used / have used) the joint Nasa-Italian Space Agency radar instrument on the European space Agency Mars Express spacecraft to ……….4………….. (gauge / gauging / gauges) the thickness and volume of ice deposits at the Martian South Pole. The ice deposits, up to 2.3 miles thick, ……….5……….. (are /were/ have been) under a polar cap of white carbon dioxide and water. Scientists have known that water ………..6…………. (exist / exists / existed) in frozen form at the Martian poles, but this research ………….7………………. (produce / produced / had produced) the most accurate measurement of just how much ice there is.

Solution

A spacecraft orbiting Mars has found huge deposits of ice at the south pole of the planet. Scientists said that if the ice deposits were in liquid form, they would be more than enough to blanket the entire planet in water.

 The scientists used the joint Nasa-Italian Space Agency radar instrument on the European space Agency Mars Express spacecraft to gauge the thickness and volume of ice deposits at the Martian South Pole. The ice deposits, up to 2.3 miles thick, are under a polar cap of white carbon dioxide and water. Scientists have known that water exists in frozen form at the Martian poles, but this research produced the most accurate measurement of just how much ice there is.