1.   But if the principal base of lunar operations is in the equatorial region, the attractiveness of polar ice is greatly diminished.

2.   Even the polar ice contains pesticide, for example.

3.   Global warming directly causes the melting of polar ice.

4.   Polar ice also would provide hydrogen for rocket fuel and for industrial processes.

5.   The use of polar ice to support such a ballistic-transportation scheme requires a substantial consumption of propellant along the way.

6.   This astonishing discovery of polar ice on Mercury makes it clear that impacts play a major role on all the terrestrial planets.

7.   With a yet slower rhythm than the polar ice, the tides of civilization ebbed and flowed across the galaxy.

8.   A total melting of polar ice, including that on Greenland, would inundate all low-lying areas.

9.   Experts say detailed knowledge of polar ice and the Arctic depths is vital for understanding such things as climate change.

10.   For the microprobes, the degree of risk depends on whether the impact site turns out to be sand dunes, polar ice or unforgiving solid rock.