stone to the stars, but it will help us learn if we can live in such a remote and harsh place for years or even a lifetime.火星地表下层可能蕴藏着丰富的冰冻水源。在火星上，一天甚至还能划分为24小时！遗憾的是，包围火星的大气中有95%是二氧化碳，火星上的气压只及地球大气压的一小部分，而且没有防紫外线层。火星宇航员必须呆在密闭的坦太空舱内，只有穿了太空服才能走出舱外。火星会成为一个卫星聚居地，就像早期地球探险者组成的边远居住区一样。火星本身也许永远不可能成为飞往周围恒星的起降点，但它有助于我们了解人类是否能够在这样一个距离遥远、条件恶劣的地方生活数年，甚至一生。（459）
Aluminum, though much less strong than steel, can be given a strength approaching that of steel when it is alloyed with small quantities of copper, manganese and magnesium, and subjected to heat treatment processes.虽然铝的强度远不及钢，但是当铝与少量的铜、蒙和镁制成合金，并经过热处理后，其强度可以接近钢。（466）
Each cylinder therefore is encased in a water jacket which forms part of circuit, through which water is pumped continuously, and cooled by means of air drawn in from the outside atmosphere by large rotary fans, worked off the main crankshaft, or in the larger diesel-electric locomotives, by auxiliary motors.因而，每个汽缸都围着一个水套，水套形成循环水路的一部分，由水泵驱动水在回路中不断地流动，并由大型旋转风扇从外部鼓入空气使水冷却。大型旋转风扇是由主曲轴带动的，而在大型电力传动内燃机车上则由辅助电动机来带动。（466）
Friction can be reduced and the life of the machines prolonged by lubrication.润滑能减少摩擦，延长机器寿命。（470）