VOA慢速英语2011--Mars Was Not Always Bitterly Cold

SCIENCE IN THE NEWS - Mars Was Not Always Bitterly Cold

 

BOB DOUGHTY¹: This is SCIENCE IN THE NEWS, in VOA Special English. I’m Bob Doughty.

BARBARA KLEIN: And I’m Barbara Klein. Today, we tell about temperature changes on the planet Mars. We also tell about a new law to protect sharks, and how melting ice is a threat to walruses³. And we tell about sounds made by fish best known for their killer⁴ bite.

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BOB DOUGHTY: Scientists at the California Institute of Technology have reported evidence that Mars was warmer and wetter long ago than it is today. The Caltech scientists say they have directly established the temperature of Mars four billion years ago. At least, they established the surface temperature on part of the planet at that time. The researchers say it is the first such evidence to be discovered and presented.

The Caltech scientists say carbonate minerals formed on Mars at about eighteen degrees Celsius⁶. They reached the finding after studying a meteorite⁸ that had its beginnings near the Martian surface.

A view from the Mars Rover Opportunity from the Western rim9 of the planet's Endeavour Crater10

Today, the average temperature on Mars is sixty-three degrees below zero Celsius.

BARBARA KLEIN: The finding was reported on the website of the Proceedings¹¹ of the National Academy of Sciences. Caltech Assistant Professor Woody Fischer helped to prepare the report. He says eighteen degrees Celsius is not especially cold or hot. He says this makes the finding extremely interesting. Knowing the temperature can give scientists an idea of the climate on Mars long ago. It can also help them decide whether the planet had liquid water.

Spacecraft orbiting Mars have shown what appear to be rivers, lakebeds and mineral deposits. These images suggest that, at one time, water did flow there. Mars Rover vehicles and other spacecraft have confirmed the information.

BOB DOUGHTY: Caltech Geology Professor John Eiler was another writer of the report. He says knowing the temperature of Mars from long ago provides valuable information. It shows that early in the planet’s history, at least part of Mars could support a climate like that of Earth.

The meteorite the scientists examined is one of the oldest known rocks in the world. It is called the Allan Hills meteorite. Its name came from the place in Antarctica where it was found in nineteen eighty-four. The meteorite is believed to have blown loose from the Mars’ surface when another space rock struck its “home.”

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BARBARA KLEIN: Earlier this year, we reported on sharks. Wildlife activists¹² worry that some kinds of sharks are in danger of disappearing. We also told how demand for shark fin⁷ soup has led to the killing¹³ of millions of sharks. The animals are harvested for meat, liver oil and, especially, for their fins¹⁴.

Sharks swimming in the Pacific Ocean about five kilometers from the coast of Hawaii

Last month, the governor of California, Jerry Brown, signed a bill that bans the sale or possession of shark fins in the state. The California Senate approved the bill in September, by a vote of twenty-five to nine.

In a statement, Governor Brown said the practice of cutting the fins off of living sharks and throwing them back in the water is not only cruel but harms the health of our oceans.

BOB DOUGHTY: Wildlife activists say seventy-three million sharks are killed each year, mainly for their fins. Sarah Sikich, of the group Heal the Bay, praised the decision to ban the sale or possession of shark fins in California. She says much of the demand for shark fins comes from the state.

SARAH SIKICH: “California is a leading importer of shark fin to the U.S. It’s estimated that eighty-five percent of the shark fin that enters the U.S. comes through California. Because the fin is driving the market value of the shark, it’s most important to target that aspect.”

A bowl of shark fin soup being served at a Chinese restaurant in the Chinatown neighborhood of San Francisco, California

California has the largest Chinese-American population in the United States – an estimated one point one million people. Some Chinese-American politicians supported the shark fin ban. But opponents have described the measure as an attack on Chinese culture. State senator Ted⁵ Lieu voted against the ban.

TED LIEU: “You can slaughter¹⁵ this highly vulnerable shark for fish and chips but a Chinese restaurant couldn’t take a shark fin from one of the hundreds of shark species (that) are nowhere near endangered and to me that is completely discriminatory and very unfair.”

The California shark fin ban will become law on January first. Existing supplies of shark fins may be sold in the state until July first, twenty-thirteen.

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BARBARA KLEIN: Thousands of big brown bodies with bright teeth spread across the Alaskan coastline this past summer. Some reports say there were as many as twenty thousand of them. No, we are not talking about holiday travelers enjoying a visit to Alaska. These were walruses! And they were looking for a place to rest, as well as something to eat.

BOB DOUGHTY: Falling ice levels in the Arctic Ocean are a threat to Pacific walruses. Earlier this year, American officials considered listing the walruses under the Endangered Species Act. The animals spend as much as two thirds of their time at sea searching for food. When not looking for food, they like to rest on large pieces of floating ice. Female walruses also take to the ice to give birth, and to care for their young.

But low summer ice levels in the Arctic forced Pacific walruses from their homes in the Chukchi Sea. The animals often search for food over the continental¹⁶ shelf of the Chukchi Sea. Low water levels make it easy for them to search the ocean floor. The Sea also has a large amount of ice, where walruses and polar bears can rest. At least, that has been the case in the past. But recent years have seen a great decrease in ice levels.

BARBARA KLEIN: Two months ago, America’s National Snow and Ice Data Center released a report about Arctic sea ice. It said ice levels this past summer measured a little more than four and one third million square kilometers. This was the second lowest level since scientists began keeping records in nineteen seventy-nine.

Scientists at the University of Bremen in Germany reported even less ice this summer than the NSIDC. Scientists blame rising temperatures for the drop in sea ice levels. They say ocean temperatures are rising around the world.

In recent years, the record low sea ice levels forced walruses to seek food and rest along the northwest coast of Alaska. But scientists fear there may not be enough food so close to the coast.

Thousands of walrus2 are congregating17 on Alaska's northwest coast because of receding18 sea ice in the Arctic

BOB DOUGHTY: More than twenty thousand walruses crowded onto the coastline earlier this year. The overcrowded conditions put younger smaller walruses at risk of being crushed. More than one hundred thirty walruses died during similar conditions in two thousand nine.

Some scientists have warned that, if temperatures continue rising, Arctic sea ice may disappear completely by twenty thirty. They say this would threaten walruses and the whole ecosystem¹⁹ in the Arctic Ocean.

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BARBARA KLEIN: Piranhas are known as dangerous, meat-eating fish. However that did not stop scientists in Belgium from working with them to learn more about the sounds these unusual fish make.

There are more than twenty different species of piranhas in the wild. Two or three of them are a threat to humans. Among them are the red-bellied piranhas. The scientists knew that red-bellied piranhas produce sounds. However it was not clear when or why they make these sounds. So a team of scientists studied red-bellied piranhas to learn more about how they communicate. The head of the team was Eric Parmentier from the University of Liege.

Using underwater microphones, the scientists recorded the sounds the fish made as they swam around and competed for food. They found that the well-fed fish were mostly quiet. But when the piranhas threatened each other over food, they produced a barking sound. It was the same sound they made when the scientists picked them up with their hands.

BOB DOUGHTY: At first the scientists thought the fish made just this one sound. But they learned that the piranhas produce two or more other sounds. When the fish are fighting for food and circling an opponent, they make a short, drum-like sound. When they bite each other, their jaws²⁰ make a softer, croaking²¹ sound.

A red-bellied piranha

Piranhas produce noises by vibrating, or moving their swim bladders. These gas-filled organs help them control their position. The scientists studied how the fish used muscles to vibrate their swim bladder, creating the sounds.

The findings were published in the Journal of Experimental Biology. Professor Parmentier and the study’s co-author, Sandie Millot of the University of Algarve in Portugal, did not complete their study without falling victim to the aggressive fish. Both scientists suffered bites while holding piranhas.

(MUSIC)

BARBARA KLEIN: This SCIENCE IN THE NEWS was written by Brianna Blake, Christopher Cruise, Jerilyn Watson and June Simms, who also was our producer. I’m Barbara Klein.

BOB DOUGHTY: And I’m Bob Doughty. 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 walrus   

n.海象

参考例句：

• He is the queer old duck with the knee-length gaiters and walrus mustache.他穿着高及膝盖的皮护腿，留着海象般的八字胡，真是个古怪的老家伙。
• He seemed hardly to notice the big walrus.他几乎没有注意到那只大海象。

3 walruses   

n.海象( walrus的名词复数 )

参考例句：

• Walruses have enormous appetites and hunt for food almost constantly. 海象食欲极大，几乎一直在猎取食物。 来自互联网
• Two Atlantic walruses snuggle on an ice floe near Igloolik, Nunavut, Canada. 加拿大努勒维特伊格卢利克附近，两头大西洋海象在浮冰上相互偎依。 来自互联网

4 killer   

n.杀人者，杀人犯，杀手，屠杀者

参考例句：

• Heart attacks have become Britain's No.1 killer disease.心脏病已成为英国的头号致命疾病。
• The bulk of the evidence points to him as her killer.大量证据证明是他杀死她的。

5 ted   

vt.翻晒，撒，撒开

参考例句：

• The invaders gut ted the village.侵略者把村中财物洗劫一空。
• She often teds the corn when it's sunny.天好的时候她就翻晒玉米。

6 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。

7 fin   

n.鳍；(飞机的)安定翼

参考例句：

• They swim using a small fin on their back.它们用背上的小鳍游动。
• The aircraft has a long tail fin.那架飞机有一个长长的尾翼。

8 meteorite   

n.陨石；流星

参考例句：

• The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
• The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。

9 rim   

n.(圆物的)边，轮缘；边界

参考例句：

• The water was even with the rim of the basin.盆里的水与盆边平齐了。
• She looked at him over the rim of her glass.她的目光越过玻璃杯的边沿看着他。

10 crater   

n.火山口，弹坑

参考例句：

• With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
• They came to the lip of a dead crater.他们来到了一个死火山口。

11 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

12 activists   

n.（政治活动的）积极分子，活动家( activist的名词复数 )

参考例句：

• His research work was attacked by animal rights activists . 他的研究受到了动物权益维护者的抨击。
• Party activists with lower middle class pedigrees are numerous. 党的激进分子中有很多出身于中产阶级下层。 来自《简明英汉词典》

13 killing   

n.巨额利润；突然赚大钱，发大财

参考例句：

• Investors are set to make a killing from the sell-off.投资者准备清仓以便大赚一笔。
• Last week my brother made a killing on Wall Street.上个周我兄弟在华尔街赚了一大笔。

14 fins   

[医]散热片；鱼鳍；飞边；鸭掌

参考例句：

• The level of TNF-α positively correlated with BMI,FPG,HbA1C,TG,FINS and IRI,but not with SBP and DBP. TNF-α水平与BMI、FPG、HbA1C、TG、FINS和IRI呈显著正相关，与SBP、DBP无相关。 来自互联网
• Fins are a feature specific to fish. 鱼鳍是鱼类特有的特征。 来自辞典例句

15 slaughter   

n.屠杀，屠宰；vt.屠杀，宰杀

参考例句：

• I couldn't stand to watch them slaughter the cattle.我不忍看他们宰牛。
• Wholesale slaughter was carried out in the name of progress.大规模的屠杀在维护进步的名义下进行。

16 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。

17 congregating   

（使）集合，聚集( congregate的现在分词 )

参考例句：

• The spatial distribution patterns of larvae and pupae are congregating distribution. 幼虫和蛹的空间分布均为聚集分布。
• He says victims of violence are congregating there because they feel safer. 他说暴力的受害者聚集在这里因为他们觉得更安全。

18 receding   

v.逐渐远离( recede的现在分词 )；向后倾斜；自原处后退或避开别人的注视；尤指问题

参考例句：

• Desperately he struck out after the receding lights of the yacht. 游艇的灯光渐去渐远，他拼命划水追赶。 来自辞典例句
• Sounds produced by vehicles receding from us seem lower-pitched than usual. 渐渐远离我们的运载工具发出的声似乎比平常的音调低。 来自辞典例句

19 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

20 jaws   

n.口部；嘴

参考例句：

• The antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。
• The scored jaws of a vise help it bite the work. 台钳上有刻痕的虎钳牙帮助它紧咬住工件。

21 croaking   

v.呱呱地叫( croak的现在分词 )；用粗的声音说

参考例句：

• the croaking of frogs 蛙鸣
• I could hear croaking of the frogs. 我能听到青蛙呱呱的叫声。 来自《简明英汉词典》