理工类考试辅导：补全对话U.S. Scientists
NASA1 scientists said that Mars was covered once by vast lakes， flowing rivers and a variety of other wet environments that had the potential to support life.
Laboratory tests aboard NASAs Phoenix Mars Lander2 have identified water in a soil sample; the landers robotic arm delivered the sample Wednesday to an instrument that identifies vapors produced by the heating of samples.
"We have water，" said William Boynton of the University of Arizona， lead scientist for the Thermal and Evolved-Gas Analyzer3， or TEGA. "This is the first time Martian water has been touched and tasted. "
The robotic arm is a critical part of the Phoenix Mars mission. It is needed to trench" into the icy layers of northern polar Mars and deliver samples to instruments that will analyze what Mars is made of， what its water is like， and whether it is or has ever been a possible habitat for life.
The soil sample came from a trench approximately 2 inches deep. When the robotic arm first reached that depth， it hit a hard layer of frozen soil. Two attempts to deliver samples of icy soil on days when fresh material was exposed were foiled when the samples became stuck inside the scoop. Most of the material in Wednesdays sample had been exposed to the air for two days， letting some of the water in the sample vaporize away and making the soil easier to handle.
"Mars is giving us some surprises，" said Phoenix principal investigator Peter Smith of the University of Arizona. "Were excited because surprises are where discoveries come from. One surprise is how the soil is behaving. The ice-rich layers stick to the scoop when poised in the sun above the deck， different from what we expected， from all the Mars simulation testing weve done so far. "
Since landing on May 25， Phoenix has been studying soil with a chemistry lab， TEGA， a microscope， a conductivity probe and cameras. The science team is trying to determine whether the water ice ever thaws enough to be available for biology and if carbon-containing chemicals and other raw materials for life are present.
The mission is examining the sky as well as the ground. A Canadian instrument is using a laser beam to study dust and clouds overhead.
"Its a 30-watt light bulb giving us a laser show on Mars，" said Victoria Hipkin of the Canadian Space Agency.
A full-circle， color panorama of Phoenixs surroundings also has been completed by the spacecraft.
"The details and patterns we see in the ground show an ice-dominated terrain as far as the eye can see，" said Mark Lemmon of Texas A & M University， lead scientist for Phoenixs Surface Stereo Imager4 camera. "They help us plan measurements were making within reach of the robotic arm and interpret those measurements on a wider scale. "
词汇：
foil v. 挫败，使成泡影 conductivity n. 传导陡，导电胜
scoop n. 铲斗 thaw v. 融化，融解
vaporize v. 使蒸发，使汽化 panorama n. 全貌，全景图
注释：
1.NASA：National Aeronautics and Space Administration(美国国家航空航天局)的缩写。NASA总部设在华盛顿哥伦比亚特区，是美国政府系统中的航空航天科研机构，负责组织和协调美国航空航天的研究工作并提供咨询。
2.Phoenix Mars Lander：凤凰号火星登陆器。其使命是探测火星地表下的冰层，分析冰层是否曾经融化产生液态水，并计划检测火星土壤是否含有生命存活的有机物。
3.Thermal and Evolved—Gas Analyzer：热力与先进气体分析仪
4.Stereo Imager：立体图像
练习：
1. What was discovered by NASAs Phoenix Mars Lander on Mars?
A)Vast lakes.
B)Flowing rivers.
C)Water in a soil sample.
D)Living things.
2. Why did the first two attempts to deliver samples fail?
A)The sample vaporized away.
B)Fresh material was exposed to the air.
C)The samples got stuck inside the scoop.
D)The robotic arm hit a hard rock.
