NASA Messenger Probe Set for Historic Orbit Around Mercury

    The U.S. space agency NASA’s Messenger probe（正直的，廉洁的） is scheduled to reach Mercury later this week, and become the first spacecraft to orbit the planet closest to the sun.
    During Messenger’s year-long orbital mission, scientists expect to learn much more about Mercury’s unique physical characteristics and environment, including its geologic¹ history and magnetic field, the composition of its core and, perhaps most importantly, whether there is frozen water at its poles. NASA astronomers² say learning more about Mercury will help them better understand the early solar system and how the Earth was formed some 4.5 billion years ago.
    Messenger was launched in August 2004, and it has taken photographs of Mercury three times during its nearly seven-year-long voyage in and around the inner solar system.  It made flybys in January and October 2008, and in September 2009.   Messenger’s pictures will be the first new data on Mercury since NASA’s Mariner³ 10 probe made three flybys in the mid-1970s.  Mariner is the only other spacecraft to have visited the innermost planet.
    The new images will allow scientists to map 98 percent of Mercury's surface, which is marked by Moon-like craters⁴, smooth plains, and long, winding⁵ cliffs.
    NASA says Messenger will briefly⁶ fire its main thruster and drop into orbit around Mercury at 0054 hours Universal time on Friday, March 18. The science leg of the mission will begin on Monday, April 4.
    Messenger's name is an acronym⁷ for the craft's multifaceted mission: "ME" for Mercury, "S" for surface, "S" for space, "EN" for environment, "GE" for geochemistry and "R" for ranging.
    Slightly larger than our moon, Mercury is the smallest planet in the solar system, but also one of the most dense⁸, with a large iron core that comprises at least 60 percent of its total mass. That is twice the density⁹ of the Earth’s core. Mercury's average distance from the Sun is just 58 million kilometers, about two-thirds closer to the sun than Earth is. It is the only other planet in the inner solar system besides Earth with a north-and-south-pole-type magnetic field.
    A single Earth year is the equivalent of four years on Mercury, which makes one lap around the sun every 88 Earth days. That makes the tiny world the "fastest" planet in the solar system. Its relatively¹⁰ swift movement across the evening skies might explain why early astronomers named the bright planet Mercury, after the winged-footed messenger of the gods in ancient Roman mythology¹¹. But Mercury rotates on its axis¹² so slowly that one of its days equals 176 days here on Earth.
    Mercury also has the widest temperature variations in the solar system.  Because of an extremely elongated¹³ solar orbit, the surface on Mercury can range from a scorching¹⁴ 425 degrees Celsius¹⁵ to a frigid¹⁶ minus 185 degrees Celsius, a range of more than 600 degrees Celsius.(本文由在线英语听力室整理编辑)

1 geologic   

adj.地质的

参考例句：

• The Red Sea is a geologic continuation of the valley.红海就是一个峡谷在地质上的继续发展。
• Delineation of channels is the first step of geologic evaluation.勾划河道的轮廓是地质解译的第一步。

2 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

3 mariner   

n.水手号不载人航天探测器，海员，航海者

参考例句：

• A smooth sea never made a skillful mariner.平静的大海决不能造就熟练的水手。
• A mariner must have his eye upon rocks and sands as well as upon the North Star.海员不仅要盯着北极星，还要注意暗礁和险滩。

4 craters   

n.火山口( crater的名词复数 )；弹坑等

参考例句：

• Small meteorites have left impact craters all over the planet's surface. 这个行星的表面布满了小块陨石留下的撞击坑。 来自《简明英汉词典》
• The battlefield was full of craters made by exploding shells. 战场上布满弹坑。 来自《现代英汉综合大词典》

5 winding   

n.绕，缠，绕组，线圈

参考例句：

• A winding lane led down towards the river.一条弯弯曲曲的小路通向河边。
• The winding trail caused us to lose our orientation.迂回曲折的小道使我们迷失了方向。

6 briefly   

adv.简单地，简短地

参考例句：

• I want to touch briefly on another aspect of the problem.我想简单地谈一下这个问题的另一方面。
• He was kidnapped and briefly detained by a terrorist group.他被一个恐怖组织绑架并短暂拘禁。

7 acronym   

n.首字母简略词，简称

参考例句：

• That's a mouthful of an acronym for a very simple technology.对于一项非常简单的技术来说，这是一个很绕口的缩写词。
• TSDF is an acronym for Treatment, Storage and Disposal Facilities.TSDF是处理，储存和处置设施的一个缩写。

8 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

9 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

10 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

11 mythology   

n.神话，神话学，神话集

参考例句：

• In Greek mythology,Zeus was the ruler of Gods and men.在希腊神话中，宙斯是众神和人类的统治者。
• He is the hero of Greek mythology.他是希腊民间传说中的英雄。

12 axis   

n.轴，轴线，中心线；坐标轴，基准线

参考例句：

• The earth's axis is the line between the North and South Poles.地轴是南北极之间的线。
• The axis of a circle is its diameter.圆的轴线是其直径。

13 elongated   

v.延长，加长( elongate的过去式和过去分词 )

参考例句：

• Modigliani's women have strangely elongated faces. 莫迪里阿尼画中的妇女都长着奇长无比的脸。
• A piece of rubber can be elongated by streching. 一块橡皮可以拉长。 来自《用法词典》

14 scorching   

adj. 灼热的

参考例句：

• a scorching, pitiless sun 灼热的骄阳
• a scorching critique of the government's economic policy 对政府经济政策的严厉批评

15 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

16 frigid   

adj.寒冷的，凛冽的；冷淡的；拘禁的

参考例句：

• The water was too frigid to allow him to remain submerged for long.水冰冷彻骨，他在下面呆不了太长时间。
• She returned his smile with a frigid glance.对他的微笑她报以冷冷的一瞥。