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SCIENCE IN THE NEWS - Signs of Water on Saturn1 Moon Enceladus; Next Close Look Set for 2008By Brianna Blake, Mario Ritter and Cynthia Kirk
Broadcast: Tuesday, April 25, 2006
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VOICE ONE:
This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty2.
VOICE TWO:
And I'm Pat Bodnar. This week: Evidence of water on one of the moons of Saturn ...
VOICE ONE:
Meet Erketu ellisoni, a newly identified dinosaur3 ...
VOICE TWO:
And warnings about the danger of hearing loss from personal music players.
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VOICE ONE:
Life on Earth requires water. When scientists look for life in other places, they look for signs of water. And they now say they have found them on a moon of Saturn.
Saturn and Cassini, an artist's version
The American spacecraft Cassini passed close to Enceladus [en-SELL-ah-dus] in February of two thousand five. Cassini captured images of what appears to be material shooting away from the moon.
The leader of the team studying the pictures of Enceladus is Carolyn Porco of the Space Science Institute in Boulder4, Colorado. She says the finding could change the way scientists look at conditions for life in the solar system.
Scientists considered several possible causes for the jet of material seen in the pictures from Cassini. But they found the most likely was that water was shooting out of Enceladus. They describe these jets as geysers, just like the boiling water that shoots out of the ground in places like Yellowstone National Park.
VOICE TWO:
The main difference between Yellowstone's geysers and those of Enceladus is temperature. Geysers on Earth are caused by heat below the ground. Ground water enters these areas, begins to heat and shoots through openings in the ground.
Scientists believe the geysers on Enceladus are only about zero degrees Celsius5 -- just above freezing. This may seem cold to us. But on Saturn's icy moon, zero degrees is very hot.
Scientific measurements show that Enceladus is very cold -- about two hundred degrees below the freezing point of water. But measurements by Cassini have shown that some parts of Enceladus are much warmer -- only one hundred sixty-degrees below freezing.
Scientists suggest that even warmer temperatures may exist below the surface of the moon. If there is liquid water, it would be much warmer than the surrounding ice. This could cause the liquid water to explode out of openings in the surface, causing the picture that Cassini captured.
VOICE ONE:
How could water exist on such a cold world? Planetary scientists have developed theories that liquid oceans exist on several icy worlds. Two moons orbiting the planet Jupiter6, Callisto and Europa, are good candidates.
Information gathered by the Voyager and Galileo space vehicles suggests that powerful forces are at work under the surfaces of these moons. The strong force of gravity from Jupiter may make underground temperatures on Callisto and Europa warm enough to melt water.
But there is a closer example of liquid water hidden under ice right here on Earth. Ten years ago, Russian and British scientists confirmed the existence of a lake in the coldest part of the world -- Antarctica. It is called Lake Vostok. It lies under four thousand meters of ice.
VOICE TWO:
There are several theories for why water in the lake remains7 liquid. One is that warmth from the Earth has melted the ice. Another is that pressure from the huge weight above the ice caused it to melt. Whatever the reason, Lake Vostok has led some scientists to believe some moons of Jupiter and now Saturn could have whole oceans hidden under their icy surface.
Cassini will get another close look at Enceladus in two thousand eight.
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You are listening to SCIENCE IN THE NEWS in VOA Special English from Washington.
VOICE ONE:
Scientists say they recently identified a new kind of dinosaur. The dinosaur belongs to the group of plant-eating creatures called sauropods. These creatures were among the largest land animals that ever lived.
Erketu ellisoni
The scientists have named the dinosaur Erketu [er-KEE-tu] ellisoni. They say its neck was more than seven meters long. But what makes Erketu ellisoni so special is the length of the neck when compared to its body. The scientists estimate the body was about three and one-half meters tall. That means the neck was probably more than two times as long as the rest of the body.
VOICE TWO:
The dinosaur's remains were found four years ago in the Gobi Desert of Mongolia. Two research scientists from the American Museum of Natural History in New York made the discovery. They described the remains in a report published in Novitates, the museum magazine.
In total, the researchers found a chest bone, two leg bones, an anklebone and several neck bones. Mark Norell said the dinosaur's secret to moving with such a long neck is found in its unusual bones. He said the bones within the neck were large but full of air holes. This made the bones very strong, while at the same time, very light.
VOICE ONE:
The researchers believe the ancient animal did not hold its neck up high in the air. Instead, they believe the neck was held out in front of the body and level with the ground.
Erketa ellisoni appears to be similar to other members of the sauropod group Titanosauria. These creatures spread throughout the world and survived until the end of the Cretaceous Period, when dinosaurs8 died off. The Cretaceous Period ended about sixty-five million years ago.
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VOICE TWO:
How loud do you listen to music?
Researchers from Zogby International did a study for the American Speech-Language-Hearing Association. It involved three hundred high school students and one thousand adults. They were asked about their use of portable9 music players like the Apple iPod. Other popular devices are CD players and laptop computers.
Forty percent of students and adults said they set the sound levels, or volume, at high on their iPods. But students were two times more likely to play the music at a very loud volume. More than half of the students said they would probably not limit their listening time. And about a third said they were not likely to reduce the volume.
VOICE ONE:
The study found that more than half of the students and less than forty percent of the adults had at least one kind of hearing loss. Some reported difficulty hearing parts of a discussion between two people. Others said they had to raise volume controls on a television or radio to hear it better. And, some experienced ringing in their ears or other noises.
Hearing experts say part of the problem is the listening equipment people are using. They say large earphones that cover the whole ear are probably safer than the smaller earbuds that come with most music players. Earbuds are thought to be less effective than earphones in blocking out foreign noises.
VOICE TWO:
Hearing loss may not be apparent10 for years. But once it happens, it is permanent. About thirty million Americans have some hearing loss. One third of them lost their hearing as a result of loud noises.
Experts at the Mayo Clinic in Minnesota say any sound above ninety decibels11 for long periods may cause some hearing loss. But most portable music players can produce sounds up to one hundred twenty decibels.
The American Speech-Language-Hearing Association is working with manufacturers and government officials on setting rules for use of portable music devices. The group says the best way to protect your hearing is to reduce the volume, limit listening time and using earphones that block out foreign noises.
VOICE ONE:
On March twenty-ninth Apple Computer announced a way for users to set a personal volume limit on the iPod Nano and fifth-generation iPod. It requires a free download of a software update from the company's Web site. Parents can also use the software to enforce a volume limit on their children's iPod with a secret combination code.
The iPod came on the market in October of two thousand one. Apple has sold more than forty million.
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VOICE TWO:
SCIENCE IN THE NEWS was written by Mario Ritter, Brianna Blake and Cynthia Kirk, who also produced our program. I'm Pat Bodnar.
VOICE ONE:
And I'm Bob Doughty. You can read and listen to our programs at www.unsv.com. To send us e-mail, write to [email protected]. And we hope you listen again next week for more news about science, in Special English, on the Voice of America.
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1
Saturn
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| n.农神，土星 | |
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doughty
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| adj.勇猛的，坚强的 | |
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dinosaur
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| n.恐龙 | |
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boulder
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| n.巨砾；卵石，圆石 | |
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Celsius
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| adj.摄氏温度计的，摄氏的 | |
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Jupiter
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| n.木星 | |
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remains
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| n.剩余物，残留物；遗体，遗迹 | |
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dinosaurs
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| n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西 | |
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portable
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| adj.轻便的，手提式的；n.便携的东西 | |
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apparent
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| adj.表面上的，貌似真实的，显然的，明明白白的 | |
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11
decibels
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| n.分贝( decibel的名词复数 ) | |
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