A.How the caves were formed on Mars. |
B.How scientists found these caves on Mars. |
C.Caves on Mars may be full of hot air or a sign of life. |
D.Scientists have completely recognized the surface of Mars. |
A.water has already been found on Mars |
B.the scientists found all the caves at night |
C.it is certain that there is life in these caves |
D.the surface of Mars is bitterly cold, radiation-soaked and dry |
A.such caves could provide energy for life |
B.they had finally found the caves on Mars |
C.such caves would be perfect places to hunt for life |
D.scientists had long been looking for these caves |
A.lave and energy |
B.water and radiation from space |
C.gases and lave |
D.water and protection from radiation |