 What is the most precious commodity on the moon?
In its last instant, the meteor fell on the Moon. Once he followed a stampede to Yellow Crater, where he thought for a while that he had a fortune in chromium. Four days reserve—plus one is five—plus sixteen days normal supply equals twenty-one days to live. It was used mostly, from sun-up to sun-down, to supplement the nuclear power plant. All of these needed water to form, and their existence on the Moon puzzled him for a while. The people on Earth saw the full moon set about the same time that the sun rose. He made trips from and to the Moon about once a month, carrying supplies in and metal and ores out.
 Water
 Water  Oxygen  Natural gas  Chromite ore