专项练习6
The approximately 65,000 images the Surveyor orbiter has beamed home in the nearly three years it has been circling Mars are full of this kind of expected hydro-scarring. But some of the pictures took scientists by surprise. The older a formation is, the more likely it is to have been distorted over the eons--smoothed by periodic windstorms or gouged by the occasional incoming meteor. However, a few of the newly discovered water channels look flesh. That discovery has lead astonished researchers to conclude that these channels may have been recently formed. Paleontologists have long assumed that if underground water was going to bubble up on Mars, it would have to be somewhere in the balmy equatorial zones, where temperatures at noon in midsummer may reach 68 degrees Fahrenheit (20 degrees Centigrade). Almost all the new channels, however, were discovered at the planet’s relative extremes--north of 30 degrees north latitude and south of 30 degrees south latitude--and all were carved on the cold, shaded sides of slopes.
【参考译文】
“探测者号”飞船在环绕火星飞行的近三年时间里传回了大约65000张图片，这些图片上满是人们预想的那种水痕。但有些图片着实让科学家们吃了一惊。一种构造越是古老，就越有可能经过了亘古岁月的扭曲——或者被周期性而来的风暴抚平，或者被偶尔从天而降的流星凿成一个个深洞。然而，有几个新发现的水渠看起来像是新近形成的。这一发现导致惊愕不已的研究人员因此得出结论：这沟渠可能是最近形成的。行星研究科学家们一直认为，如果地下水是从火星的地表下冒出来的，它可能是在温暖潮湿的赤道地区，那里的气温在仲夏正午时候能高达华氏68度(摄氏20度)。然而，几乎所有这些新的沟渠都是在火星偏向两极的地方发现的——北纬30度以北，南纬30度以南——而且所有这些痕迹都刻在寒冷的山坡背阴处。