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VOA慢速英语2011--ut Fireflies and Possible Liquid Water o

时间:2011-08-30 02:56:56

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SCIENCE IN THE NEWS - All About Fireflies and Possible Liquid Water on Mars

CHRISTOPHER CRUISE: This is SCIENCE IN THE NEWS, in VOA Special English. I’m Christopher Cruise.
BOB DOUGHTY1: And I’m Bob Doughty. Today, we tell about evidence of liquid water on the planet Mars. We also consider a theory that the Earth once had a small second moon. And we celebrate summertime with a report about creatures known to light up the night sky.
(MUSIC)
CHRISTOPHER CRUISE: An American spacecraft orbiting Mars shows it is possible that the planet could someday support human life. The Mars Reconnaissance Orbiter has found the best evidence yet that liquid water flows on Mars during the planet’s warm season.
Charles Bolden heads the National Aeronautics2 and Space Administration. He says NASA’s Mars Exploration Program keeps bringing scientists closer to learning if Mars could support some form of life. He says the program has shown that the planet is an important goal for future human exploration.
BOB DOUGHTY: The Mars Reconnaissance Orbiter studied many mountain slopes across the planet’s southern hemisphere. The dark lines of mountain sides are said to look like fingers. The marks appear and disappear with the seasons.
The marks appear when temperatures on Mars rise. They look larger as they go downhill. When it gets cold, these streaks3 disappear. But they are seen again on the planet during the next spring, or warming season.
CHRISTOPHER CRUISE: Alfred McEwen is lead investigator4 for the orbiter’s High Resolution Imaging Science Experiment. He also is a professor of planetary geology at the University of Arizona in Tucson. Professor McEwen says a flow of briny5, or salty, water is the best explanation for the orbiter’s observations. Other spacecraft and Martian meteorites6 have shown that the Martian surface is salty.
The professor says the water on Mars may differ from that found on Earth. He says the Mars water might be more like a thick fluid. “Science” magazine published a report about the orbiter’s findings.
BOB DOUGHTY: Professor McEwen and his team believe that water probably flowed across ancient Mars. But whether water exists as a liquid on the Red Planet can still be debated. The iron oxide7 on Mars gives the planet its reddish color.
Philip Christensen is an expert in geological science at Arizona State University. He says scientists have known for years that ice existed on Mars.
PHILIP CHRISTENSEN: “We know Mars has a lot of ice. But this is the first time we have seen the potential for liquid water. It might be salty water. But it is still liquid. And I think that is the real key here. It is not that Mars does not have a lot of ice. But liquid water – certainly to an organism – is very, very very different than ice.”
Geology expert Lisa Pratt of Indiana University welcomes the research results. She says the discovery will help scientists plan future travels to look for life signs on present-day Mars.
(MUSIC)
CHRISTOPHER CRUISE: “Blue moons, you saw me standing8 alone.” The cow jumped over the moons. “Shine on Harvest Moons.” These expressions sound unusual. Why the choice of “moons” and not just “moon?” There is only one moon, right? Yes, there is only one, but long ago there might have been two!
American and Swiss researchers say the Earth may once have had a big moon, the one that is still there, and a little moon. And then, about four billion years ago, they hit each other. The little moon exploded into rock and dust, and much of it landed on the dark side of the larger moon. The researchers call it the “big splat.”
Scientists from the University of California at Santa Cruz and the University of Bern reported their findings in “Nature” magazine. The scientists say the little moon was very small, only about one thousand two hundred kilometers across. They say the little moon and the big moon were just fine together for one hundred million years. Then something happened and the little moon lost the battle.
BOB DOUGHTY: The Earth and the moon turn in a way that keeps the dark side of the moon away from us. From earth, we see only one side. But we know what the other side looks like. Spacecraft have taken many pictures of the dark side. Those pictures show that the side of the moon we see is a lot different from its other side.
Our side has ridges9 or hills, and craters10, some of them deep. But it is not nearly so “bumpy” as the dark side. Researchers think this is because the little moon crashed, fell apart, and landed on the other side. They say the dark side has a thick upper layer of soil. It also has much higher mountains than on the side we see. Some of them are three thousand meters high. And when the little moon hit the big moon, it caused a bulge11. The other side of the moon sticks out into space more. Think of a children’s ball that has been hit or kicked too much. That ball, and our moon, are no longer round. They are lop-sided. Pictures of the dark side clearly show this.
CHRISTOPHER CRUISE: You may be wondering how our moon got there in the first place. Scientists think it also resulted from a crash. Billions of years ago, they say, something very large hit the earth. It may have been as big as the planet Mars. When that happened, part of the earth was thrown out into space. Over time, these pieces of earth-rock and dust came together, and formed not one, but two moons.
The American space agency plans to explore the moon further within the next year. That may help to prove the two-moon crash idea, or maybe offer something completely new. But if the latest research is correct, what is now one, was once two!
(MUSIC)
JIM TEDDER12: Imagine a summer night in America. A father and mother are watching television or reading the newspaper. Their children are outside the house, playing and waiting for a special time. Then, just as it starts to get very dark, the magic begins.
CHILD’S VOICE: “Look (blip) there’s one over there … (blip) and another over there! Look (blip blip blip) three more … near the tree. Let’s catch ‘em.”
BOB DOUGHTY: What they would like to catch and put into a glass jar are coleoptera: flying beetles13 better known as “fireflies” or “lightning bugs15.”
Scientists say there are about two thousand kinds of these insects. Most are brown. Each is only about a centimeter long. Fireflies have wings folded over their backs. When they fly, they do so in an unusual way. Some people say they fly in the shape of the letter “J.” That means they fly horizontally, then drop quickly, only to rise again. But the most surprising thing about these little creatures is that they make light.
They do this by the process known as bioluminescence. Oxygen mixes with chemicals in the body of the lightning bug14. Then, for a second, its belly16 lights up. Some produce a flash of yellow light. Others appear green or red. But why do they do this?
CHRISTOPHER CRUISE: Entomologists, people who study insects, think the flashing light is an invitation to have sex. They believe the male firefly is making a signal to a female waiting in the grass. He is saying, “Look, here I am. Let’s get together.” If the female agrees, she will answer with a flash of her own. Studies at the University of Kansas have shown that females like males who can flash the fastest.
In some parts of the world, fireflies act in an amazing way. Thousands of them flash their light on and off at the same time. This can often be seen in Malaysian jungles and in the American states of Tennessee and South Carolina.
Scientists do not know how lightning bugs are able to communicate with each other to do this. But they think it is either a call for sex, or a warning sign from the bugs to their enemies. Insects with lights carry chemicals that do not taste good. Some of those chemicals, however, are useful to people. Health researchers use them in the study of cancer, heart disease, multiple sclerosis, and cystic fibrosis.
BOB DOUGHTY: Fireflies live for about three years. Most of that time is spent in the ground as larvae17. Some people call it a “glow worm” before it becomes a flying adult. And yes, glow worms … larvae … do, indeed, glow. Scientists say these little bugs only come out in warm weather, and only at night. During the day, they hide on the ground or in trees or other plants.
Wherever there is light, there is heat. A common light bulb wastes ninety percent of the energy it uses in the form of heat. But a lightning bug produces “cold light.” That means that most of its flash is true light. Only about three percent of its energy comes as heat.
After three years, the life of a lightning bug’s life is done. The females bury their eggs in the ground, and the birth and death cycle starts all over again, just as it has for millions of years.
JIM TEDDER: Summertime in America: ice cream, baseball games, and, yes, (blip blip blip) fireflies at the close of another day.
(MUSIC)
CHRISTOPHER CRUISE: This SCIENCE IN THE NEWS was written by Jerilyn Watson and Jim Tedder, who you also heard on our program. Our producer was June Simms. I’m Christopher Cruise.
BOB DOUGHTY: And I’m Bob Doughty.Visit us at voaspecialenglish.com, where you can find transcripts18 and MP3s of our reports. Join us again next week for more news about science in Special English on the Voice of America.


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点击收听单词发音收听单词发音  

1 doughty Jk5zg     
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 aeronautics BKVyg     
n.航空术,航空学
参考例句:
  • National Aeronautics and Space undertakings have made great progress.国家的航空航天事业有了很大的发展。
  • He devoted every spare moment to aeronautics.他把他所有多余的时间用在航空学上。
3 streaks a961fa635c402b4952940a0218464c02     
n.(与周围有所不同的)条纹( streak的名词复数 );(通常指不好的)特征(倾向);(不断经历成功或失败的)一段时期v.快速移动( streak的第三人称单数 );使布满条纹
参考例句:
  • streaks of grey in her hair 她头上的绺绺白发
  • Bacon has streaks of fat and streaks of lean. 咸肉中有几层肥的和几层瘦的。 来自《现代英汉综合大词典》
4 investigator zRQzo     
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。
5 briny JxPz6j     
adj.盐水的;很咸的;n.海洋
参考例句:
  • The briny water is not good for the growth of the trees.海水不利于这种树木的生长。
  • The briny air gave a foretaste of the nearby sea.咸空气是快近海的前兆。
6 meteorites 12efd1ed528a28fe1f7cb667a7fbc1e0     
n.陨星( meteorite的名词复数 )
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》
  • One theory about the existence of extraterrestrial life rests on the presence of carbon compounds in meteorites. 地球外存在生命的理论是基于陨星上存在碳化合物质这一事实的。 来自《简明英汉词典》
7 oxide K4dz8     
n.氧化物
参考例句:
  • Oxide is usually seen in our daily life.在我们的日常生活中氧化物很常见。
  • How can you get rid of this oxide coating?你们该怎样除去这些氧化皮?
8 standing 2hCzgo     
n.持续,地位;adj.永久的,不动的,直立的,不流动的
参考例句:
  • After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
  • They're standing out against any change in the law.他们坚决反对对法律做任何修改。
9 ridges 9198b24606843d31204907681f48436b     
n.脊( ridge的名词复数 );山脊;脊状突起;大气层的)高压脊
参考例句:
  • The path winds along mountain ridges. 峰回路转。
  • Perhaps that was the deepest truth in Ridges's nature. 在里奇斯的思想上,这大概可以算是天经地义第一条了。
10 craters 1f8461e3895b38f51c992255a1c86823     
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》
11 bulge Ns3ze     
n.突出,膨胀,激增;vt.突出,膨胀
参考例句:
  • The apple made a bulge in his pocket.苹果把他口袋塞得鼓了起来。
  • What's that awkward bulge in your pocket?你口袋里那块鼓鼓囊囊的东西是什么?
12 tedder 2833afc4f8252d8dc9f8cd73b24db55d     
n.(干草)翻晒者,翻晒机
参考例句:
  • Jim Tedder has more. 吉姆?特德将给我们做更多的介绍。 来自互联网
  • Jim Tedder tells us more. 吉姆?泰德给我们带来更详细的报道。 来自互联网
13 beetles e572d93f9d42d4fe5aa8171c39c86a16     
n.甲虫( beetle的名词复数 )
参考例句:
  • Beetles bury pellets of dung and lay their eggs within them. 甲壳虫把粪粒埋起来,然后在里面产卵。 来自《简明英汉词典》
  • This kind of beetles have hard shell. 这类甲虫有坚硬的外壳。 来自《现代汉英综合大词典》
14 bug 5skzf     
n.虫子;故障;窃听器;vt.纠缠;装窃听器
参考例句:
  • There is a bug in the system.系统出了故障。
  • The bird caught a bug on the fly.那鸟在飞行中捉住了一只昆虫。
15 bugs e3255bae220613022d67e26d2e4fa689     
adj.疯狂的,发疯的n.窃听器( bug的名词复数 );病菌;虫子;[计算机](制作软件程序所产生的意料不到的)错误
参考例句:
  • All programs have bugs and need endless refinement. 所有的程序都有漏洞,都需要不断改进。 来自《简明英汉词典》
  • The sacks of rice were swarming with bugs. 一袋袋的米里长满了虫子。 来自《简明英汉词典》
16 belly QyKzLi     
n.肚子,腹部;(像肚子一样)鼓起的部分,膛
参考例句:
  • The boss has a large belly.老板大腹便便。
  • His eyes are bigger than his belly.他眼馋肚饱。
17 larvae w2CxP     
n.幼虫
参考例句:
  • Larvae are parasitic on sheep.幼虫寄生在绵羊的身上。
  • The larvae prey upon small aphids.这种幼虫以小蚜虫为食。
18 transcripts 525c0b10bb61e5ddfdd47d7faa92db26     
n.抄本( transcript的名词复数 );转写本;文字本;副本
参考例句:
  • Like mRNA, both tRNA and rRNA are transcripts of chromosomal DNA. tRNA及rRNA同mRNA一样,都是染色体DNA的转录产物。 来自辞典例句
  • You can't take the transfer students'exam without your transcripts. 没有成绩证明书,你就不能参加转学考试。 来自辞典例句

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