Horizon - Life On Mars 火星生命 - 6

For Mars to have rivers, it must once have had streams, rain, clouds and an atmosphere, a planet just like the Earth today-if these were rivers. They had to be sure.

The answers would come in 1998 with the launch of Mars Global Surveyor. It was equipped with the latest high-resolution electronic cameras. Sections of the valleys were revealed in fantastic detail. Some valleys had been eroded¹ and filled in with sand. It was impossible to say how they'd been formed. They could have been carved by water, or soil, or carbon dioxide. Then, after they'd searched through thousands of images they found this- a winding² valley, two kilometers wide, and at a bend in the canyon³, a tiny channel, the unmistakable trace of an ancient river.

This is the best evidence we have that climate in the past was different from what it is today.

Only a river would leave a meandering⁴ trace like this. Only a river would leave the traces of silt⁵ they saw in the bend, and only water could carve the winding channel feeding into it. But they soon found more than just a few rivers. They discovered evidence that water had once existed on Mars in colossal⁶ quantities.

The evidence came from another probe that reached Mars in 1997. It landed in an enormous channel and sent back images of huge boulders⁷ scattered⁸ around the Martian surface. Scientists were puzzled. What could this strange pattern signify? One man looking on knew exactly what those scattered stones meant-Jim Rice.


Mars Global Surveyor:U. S. mission to Mars launched in 1996. Main instruments include a camera, laser altimeter, thermal⁹ emission¹⁰ spectrometer, and magnetometer. During the primary mission, the spacecraft circled the planet once every 118 minutes at an average altitude of 378 kilometers (235 miles). The extended mission phase began February 1, 2001. The spacecraft may function eventually as a communications satellite to relay data back to Earth from surface landers launched as part of future Mars missions

meander:to follow a winding and turning course
meandering:winding

1 eroded   

adj. 被侵蚀的，有蚀痕的 动词erode的过去式和过去分词形式

参考例句：

• The cliff face has been steadily eroded by the sea. 峭壁表面逐渐被海水侵蚀。
• The stream eroded a channel in the solid rock. 小溪在硬石中侵蚀成一条水道。

2 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。

3 canyon   

n.峡谷，溪谷

参考例句：

• The Grand Canyon in the USA is 1900 metres deep.美国的大峡谷1900米深。
• The canyon is famous for producing echoes.这个峡谷以回声而闻名。

4 meandering   

蜿蜒的河流，漫步，聊天

参考例句：

• The village seemed deserted except for small boys and a meandering donkey. 整个村子的人都像是逃光了，只留下了几个小男孩和一头正在游游荡荡的小毛驴。 来自教父部分
• We often took a walk along the meandering river after supper. 晚饭后我们常沿着那条弯弯曲曲的小河散步。

5 silt   

n.淤泥，淤沙，粉砂层，泥沙层；vt.使淤塞；vi.被淤塞

参考例句：

• The lake was almost solid with silt and vegetation.湖里几乎快被淤泥和植物填满了。
• During the annual floods the river deposits its silt on the fields.每年河水泛滥时都会在田野上沉积一层淤泥。

6 colossal   

adj.异常的，庞大的

参考例句：

• There has been a colossal waste of public money.一直存在巨大的公款浪费。
• Some of the tall buildings in that city are colossal.那座城市里的一些高层建筑很庞大。

7 boulders   

n.卵石( boulder的名词复数 )；巨砾；（受水或天气侵蚀而成的）巨石；漂砾

参考例句：

• Seals basked on boulders in a flat calm. 海面风平浪静，海豹在巨石上晒太阳。 来自《简明英汉词典》
• The river takes a headlong plunge into a maelstrom of rocks and boulders. 河水急流而下，入一个漂砾的漩涡中。 来自《简明英汉词典》

8 scattered   

adj.分散的，稀疏的；散步的；疏疏落落的

参考例句：

• Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来，塞进文件夹里。

9 thermal   

adj.热的，由热造成的；保暖的

参考例句：

• They will build another thermal power station.他们要另外建一座热能发电站。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

10 emission   

n.发出物，散发物；发出，散发

参考例句：

• Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施，降低污染物排放总量。
• Finally,the way to effectively control particulate emission is pointed out.最后，指出有效降低颗粒排放的方向。