问答题 Time was when the solar system had two watery worlds. 46) Directly next door to the warm. wet, loamy Earth was the warm, wet, loamy Mars, both planets covered with oceans and running with rivers-and both possibly teeming with life. Billions of years ago, however, the low-gravity Mars had both its air and water leak away, causing the planet to become the dead, freeze-dried place it is today.
That is what the prevailing thinking has been. Now, it appears that thinking may be wrong. 47) Recently, NASA released new images from the Mars Global Surveyor spacecraft that suggest water may be flowing up and streaming onto the Martian surface-dramatically increasing the likelihood that at least part of the planet is biologically alive. "If these results prove true," says Ed Weiler, associate administrator of NASA's Office of Space Science, "[they have] profound implications for the possibility of life."
Finding liquid water on Mars' surface has never been easy-because it simply can't exist there. The modern-day Martian atmosphere has barely 1 percent the density of Earth's, and its average temperature hovers around-67 degrees Fahrenheit (-19 degrees Centigrade) . In an environment as harsh as this, water would either vaporize into space or simply flash-freeze in place. 48) Scientists studying Martian history have always looked for clues the planet's ancient water left behind-tracks where vanished rivers once flowed, basins where vanished seas once stood.
49) 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 fresh. That discovery has lead astonished researchers to conclude that these channels may have been recently formed.
50) planetologists 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.

【正确答案】与温暖、潮湿和遍布土壤的地球毗邻的火星,也曾经是一个温暖、潮湿和遍布土壤的星球,两个行星都覆盖着海洋、奔淌着河流,而且都可能充满生命。
【答案解析】
【正确答案】最近,美国国家航空航天局发布了从“火星全球探测者号”宇宙飞船上传回来的新图片,从这些图片可以看出,水可能正在火星流淌或者涌出火星表面——这极大地增加了至少这个星球的部分表面存在有生命的可能性。
【答案解析】
【正确答案】研究火星史的科学家们一直在寻找这个星球上古远的水曾经留下的线索——消失的河流曾经流淌过的印迹,或者是消逝的海洋曾经覆盖的盆地。
【答案解析】
【正确答案】“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,这些图片上满都是人们预想的那种水痕迹。
【答案解析】
【正确答案】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)。
【答案解析】