The next great land area that man hopes to colonize is the moon. In size it is near equal to the area of North and 【M1】______ South America. However, it presents a hostile environment that temperatures range from + 120 to- 150 【M2】______ degrees Centigrade. There is no air, no water. Today there is considerate scientific speculation about 【M3】______ living on the mood. When man will begin life on the lunar surface is still not determined. So experts believe that 【M4】______ colonization will take place in three steps. First, there will be increasing periods of exploration with temporarily 【M5】______ shelters. These periods will be followed by longer stays with housing Under the surface of the moon and daily necessities brought by the colonizers theirself. Finally, 【M6】______ colonies that are self-supporting will be established. The principal job of the early settlers will be to stay living. They will have to plant crops under huge domes (圆 【M7】______ 顶建筑) to produce food and oxygen and find water sources. When this has done, the settlers will have time to 【M8】______ explore the possibilities of commercial development and to make discoveries important to science. The characteristics of the moon that makes it had for 【M9】______ human survival may make it ideal for certain kinds of manufacturing. Operations required a vacuum, extreme 【M10】______ cold are examples. Precision ball bearings, and industrial diamonds might be produced on the moon. 【M1】