VOA慢速英语 2008 0408b

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.

VOICE TWO:

And I'm Bob Doughty¹. This week, we will tell about icy material shooting up from a moon of the planet Saturn². We will also tell about an experimental drug for the disease schistosomiasis. And, we tell about a new study of the Grand Canyon³ -- one of America's greatest natural wonders.

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VOICE ONE:
　

Enceladus, photographed by the Cassini spacecraft

Saturn is best known for the rings of icy material that surround the planet. But Saturn's moons interest scientists because some may hold liquid water and other materials necessary for life.

Recently, the American space agency NASA ordered the Cassini spacecraft to visit one of Saturn's most interesting moons. NASA jointly⁴ operates Cassini with the European Space Agency and the Italian Space Agency.

The moon is Enceladus. It is not Saturn's largest moon. It is only five hundred kilometers across. But the forces that affect the surface of Enceladus are very active.

VOICE TWO:

Periodically, huge amounts of material shoot up from the surface. NASA officials have called these events geysers, like the hot water that is forced out from under the ground on Earth. Cassini first captured pictures of such an event three years ago. The pictures have proved so scientifically important that NASA made changes to its plans for Cassini just to study the geysers.

On March twelfth, the space agency directed Cassini to pass only about fifty kilometers from the surface of Enceladus. Cassini got so close that it passed through material shooting out of the moon. The spacecraft was traveling at a speed of fifteen kilometers a second.

VOICE ONE:

What Cassini found has only increased scientists' interest in the moon. New maps of temperatures on Enceladus show that an area on the southern part of the moon is ninety-three degrees below zero Celsius⁵. Temperatures on Enceladus are normally about one hundred thirty degrees below zero.

John Spencer is a scientist at the Southwest Research Institute in Boulder⁶, Colorado. He says the new temperature information makes it more likely that there is liquid water not far below the surface.

Liquid water is believed to be one of the things needed for life. Organic material is another. Cassini also found that the geysers are releasing organic material.

VOICE TWO:

Hunter Waite is an investigator⁷ for the Cassini Ion and Neutral Mass Spectrometer at the Southwest Research Institute in San Antonio, Texas. The spectrometer is a device that helps identify the chemistry of substances.

Mister Waite says the chemicals gathered from the geysers of Enceladus are much like those found on comets in our solar system. Cassini found water, carbon dioxide, carbon monoxide and also organic material shooting from the geyser.

It is not known what causes the geysers on Enceladus. Cassini's deputy project scientist, Linda Spilker, says scientists know that heat causes the geysers to shoot from the surface of Enceladus. But, she says, it is not known what causes the heat.

VOICE ONE:

Gravity from Saturn and the moon Dione are known to affect Enceladus. But it is not clear if this gravitational force is enough to cause the moon's energetic geysers.

The geysers are powerful. The material is leaving the surface at four hundred meters a second. And there is a link between the geysers and the objects for which Saturn is most famous. Material from Enceladus helps form the E-ring, the most distant of Saturn's many beautiful rings.

The most recent visit is only the beginning of close study of Enceladus. Scientists will have another chance to observe Enceladus when Cassini passes very near the moon again in August.

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VOICE TWO:

Scientists think they are a step closer to a new drug to treat schistosomiasis. More than two hundred million people suffer from this parasitic⁸ worm disease. Most live in developing nations. About ten percent of victims become seriously disabled from internal bleeding, iron loss, organ damage or other effects.

A team in the United States found that chemical compounds known as oxadiazoles can attack an enzyme⁹ needed for the survival of Schistosoma. This is the group of flatworms that cause schistosomiasis.

VOICE ONE:

The scientists tested oxadiazoles on laboratory mice. They found that one compound killed the parasite¹⁰ at every level of development. The study also showed that the compound was active against all three major kinds of Schistosoma worms that infect human beings.

America's National Institutes of Health supported the research. Nature Medicine magazine reported on the study by scientists from Illinois State University and the Chemical Genomics Center at N.I.H.

David Williams led the research. He says the Schistosoma parasite needs oxygen to survive. Oxygen use produces oxygen-free radicals¹¹ that can destroy an organism. The worm has a protective enzyme. But Professor Williams says the experimental drug disables this enzyme, causing the worm to self-destruct.

VOICE TWO:

Each year, two hundred eighty thousand people die of schistosomiasis, also known as bilharzia or snail¹² fever. The microscopic¹³ worms infect snails¹⁴, which produce infected eggs. People become infected when they enter fresh water where the snails live.

The worms dig through skin to enter the body. They move into blood passages that supply the intestinal¹⁵ and urinary systems. Then, if worm eggs in human waste enter fresh water, more snails and people become infected.

VOICE ONE:

Since the nineteen eighties, doctors have used one main drug to treat schistosomiasis. Public health experts worry that the worms will become resistant¹⁶ to this drug, praziquantel.

More studies are needed on the experimental drug. The scientists say the results in mice were better than all the targets set by the World Health Organization for new schistosomiasis compounds. They hope the drug will be ready for testing in humans in four to five years.

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VOICE TWO:
　

Grand Canyon

Scientists in the United States say the Grand Canyon is nearly three times as old as earlier estimates. They say they found evidence that the Grand Canyon began forming seventeen million years ago. That is eleven million years earlier than other studies have shown.

Geologists¹⁷ at the University of New Mexico carried out the new study. Their findings were published last month in Science magazine.

Other scientists say the findings fit with earlier theories about how the Grand Canyon may have been formed. But some experts on Earth's development disagree. They say the study fails to support earlier findings.

VOICE ONE:

The Grand Canyon is a popular stop for visitors to the southwestern United States. It stretches up to twenty-nine kilometers wide and nearly two kilometers deep. Yet its age has long been an issue of scientific debate.

Scientists have often used geologic¹⁸ events to describe the history of the Grand Canyon. Such events have included rock flows and sedimentary rock, or rock formed from other rocks. Generally, this method is only able to confirm ages of rock formations up to one million years ago.

VOICE TWO:

Instead, the American geologists used a uranium-lead dating method that finds ages of minerals back tens to hundreds of millions of years. They dated minerals from caves at different depths of the canyon’s walls. Minerals from openings on hillsides are less likely to suffer damage from water or other causes of erosion.

The uranium-lead dating system helped the geologists estimate water levels over time as river water cut through the rock to form the Grand Canyon. Their findings suggest that the rate of erosion was much slower in the western canyon than in the eastern part.

VOICE ONE:

Today the Colorado River runs along the four hundred forty-six kilometer long canyon. Based on their findings, the geologists believe a separate river began the formation of the Grand Canyon. They say the canyon started instead from the west by a river about seventeen million years ago. Another river began forming a canyon from the east. Over time, the rivers connected to each other. The geologists estimate the two canyons¹⁹ joined together about six million years ago.

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VOICE TWO:

This SCIENCE IN THE NEWS was written by Brianna Blake, Jill Moss²⁰ and Mario Ritter. Brianna Blake was also our producer. I'm Bob Doughty.

VOICE ONE:

And I'm Barbara Klein. Read and listen to our programs at voaspecialenglish.com. Join us again next week for more news about science in Special English on the Voice of America.

1 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。

2 Saturn   

n.农神，土星

参考例句：

• 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。
• These comparisons suggested that Saturn is made of lighter materials.这些比较告诉我们，土星由较轻的物质构成。

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 jointly   

ad.联合地，共同地

参考例句：

• Tenants are jointly and severally liable for payment of the rent. 租金由承租人共同且分别承担。
• She owns the house jointly with her husband. 她和丈夫共同拥有这所房子。

5 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。

6 boulder   

n.巨砾；卵石，圆石

参考例句：

• We all heaved together and removed the boulder.大家一齐用劲，把大石头搬开了。
• He stepped clear of the boulder.他从大石头后面走了出来。

7 investigator   

n.研究者，调查者，审查者

参考例句：

• He was a special investigator for the FBI.他是联邦调查局的特别调查员。
• The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。

8 parasitic   

adj.寄生的

参考例句：

• Will global warming mean the spread of tropical parasitic diseases?全球变暖是否意味着热带寄生虫病会蔓延呢？
• By definition,this way of life is parasitic.从其含义来说，这是种寄生虫的生活方式。

9 enzyme   

n.酵素，酶

参考例句：

• Above a certain temperature,the enzyme molecule will become unfolded.超过一定温度，酶分子将会展开。
• An enzyme that dissolves the fibrin of blood clots.能溶解血凝块中的纤维的酶。

10 parasite   

n.寄生虫；寄生菌；食客

参考例句：

• The lazy man was a parasite on his family.那懒汉是家里的寄生虫。
• I don't want to be a parasite.I must earn my own way in life.我不想做寄生虫，我要自己养活自己。

11 radicals   

n.激进分子( radical的名词复数 )；根基；基本原理；[数学]根数

参考例句：

• Some militant leaders want to merge with white radicals. 一些好斗的领导人要和白人中的激进派联合。 来自《简明英汉词典》
• The worry is that the radicals will grow more intransigent. 现在人们担忧激进分子会变得更加不妥协。 来自辞典例句

12 snail   

n.蜗牛

参考例句：

• Snail is a small plant-eating creature with a soft body.蜗牛是一种软体草食动物。
• Time moved at a snail's pace before the holidays.放假前的时间过得很慢。

13 microscopic   

adj.微小的，细微的，极小的，显微的

参考例句：

• It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
• A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。

14 snails   

n.蜗牛；迟钝的人；蜗牛( snail的名词复数 )

参考例句：

• I think I'll try the snails for lunch—I'm feeling adventurous today. 我想我午餐要尝一下蜗牛——我今天很想冒险。 来自《简明英汉词典》
• Most snails have shells on their backs. 大多数蜗牛背上有壳。 来自《简明英汉词典》

15 intestinal   

adj.肠的；肠壁；肠道细菌

参考例句：

• A few other conditions are in high intestinal obstruction. 其它少数情况是高位肠梗阻。 来自辞典例句
• This complication has occasionally occurred following the use of intestinal antiseptics. 这种并发症偶而发生在使用肠道抗菌剂上。 来自辞典例句

16 resistant   

adj.(to)抵抗的，有抵抗力的

参考例句：

• Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。
• They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。

17 geologists   

地质学家，地质学者( geologist的名词复数 )

参考例句：

• Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
• Geologists study the structure of the rocks. 地质学家研究岩石结构。

18 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。

19 canyons   

n.峡谷( canyon的名词复数 )

参考例句：

• This mountain range has many high peaks and deep canyons. 这条山脉有许多高峰和深谷。 来自辞典例句
• Do you use canyons or do we preserve them all? 是使用峡谷呢还是全封闭保存？ 来自互联网

20 moss   

n.苔，藓，地衣

参考例句：

• Moss grows on a rock.苔藓生在石头上。
• He was found asleep on a pillow of leaves and moss.有人看见他枕着树叶和苔藓睡着了。