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SCIENCE IN THE NEWS - Spacecraft Comes Home With Stardust Memories of the Solar System

来源:慢速英语   时间:2011-01-29 22:09:18


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


And I’m Pat Bodnar. This week on our show: Star dust memories of our solar system ...


Measuring the effects of world trade on global warming ...


And are frogs feeling the heat from higher world temperatures?


Lead scientist Donald Brownlee makes a victory sign as material from the Stardust capsule is examined

On January fifteenth, a long-awaited American spacecraft returned safely to Earth. The flight lasted seven years and more than four thousand million kilometers. It carried home a small amount of star dust and space dust from the tail of the comet called Wild-Two.

And yes, the engineers and scientists who waited all these years were wildly happy.


Donald Brownlee of the University of Washington in Seattle is the lead investigator on the Stardust program for the NASA space agency. He described the contents of the capsule as a treasure from the edge of the solar system.

NASA launched the Stardust spacecraft toward the path of Wild-Two in nineteen ninety-nine. In January of two thousand four, the ship came within two hundred forty kilometers of the comet.

Stardust opened a collector to capture material from the comet's tail. Inside the collector was a substance called aerogel to trap particles floating in space. Aerogel weighs almost nothing. It looks a lot like smoke. Scientists call it glass smoke.


Stardust meets the comet, an artist's version

Comets are often called "dirty snowballs." Scientists say they contain materials left over from the huge cloud of gas and dust that formed into the sun and the planets.

Stardust spent about six months collecting particles. Then the robotic craft moved the collector into a sample return capsule, and headed for Earth.

On January fourteenth, Stardust released the forty-five-kilogram capsule. It happened about one hundred ten thousand kilometers above the Earth. That capsule is what landed at an Air Force testing ground in the desert of the western state of Utah. It shot through the atmosphere at about forty-five thousand kilometers an hour, a record speed for a spacecraft re-entry.

Now, scientists expect to learn more about the birth of the solar system more than four and one-half thousand million years ago. In fact, Donald Brownlee says some of the captured particles are sure to be older than the sun.


The scientists and engineers were tense as they awaited the return of the Stardust capsule. Then they saw long-distance images of an open parachute.

In two thousand four, NASA watched the return of a similar spacecraft, Genesis. It returned with material expelled from the sun. Its parachute, however, failed. Genesis crashed into the Utah desert. It broke open, but scientists have said it could still have some research value.



This is SCIENCE IN THE NEWS, in VOA Special English from Washington.

A new study finds a direct link between the warming of the Earth’s atmosphere and the loss of some kinds of creatures.

The study involved brightly colored frogs that live in mountain forests of Central and South America. There were about one hundred ten kinds of these harlequin frogs twenty years ago. Now, scientists say, more than seventy have disappeared.

Experts believe that a fungus killed them. The bacterial disease has attacked frogs and other amphibians around the world. Amphibians live on land and in water. They are considered easy victims because of their thin skin.


But the new study found that the losses of harlequin frogs happened in years with sharp increases in world temperatures. American biologist Alan Pounds led the study. He says the timing of the events shows a "very clear relationship." Mister Pounds works at the Monteverde Cloud Forest Preserve and Tropical Science Center in Costa Rica.

Yet the fungus grows best in cooler temperatures. The scientists offer an explanation. They say warmer weather led to more water in the air, which led to more clouds. The cloud cover produced cooler days, though the nights got warmer. The scientists say the conditions helped spread the fungus. They say the recent losses are tied to global warming.

But other scientists are not so sure. Some criticized the new study. They say it did not consider other environmental changes that could have affected the frogs.


Scientists say more than one hundred species of amphibians around the world have disappeared since nineteen eighty. Some say almost one-third of the world's six thousand different frogs, toads and salamanders are threatened.

Ecologist Karen Master took part in the study. She says many ecological systems are at risk from global warming. She says eighteen to thirty-five percent of plant and animal populations could disappear in the next forty-five years.

Researchers say climate change is also a danger to humans. The World Health Organization says higher temperatures are helping to spread diseases tied to insects and water. As a result, it estimates that an additional one hundred fifty thousand people will die this year and five million others will get sick.


Periods of warming and cooling are normal for Earth. But scientists widely believe that human activity is responsible for most of the recent warming. They say carbon dioxide and others gases from factories and vehicles trap extra heat in the atmosphere.

The Earth’s average temperature rose by about six-tenths of one degree Celsius in the twentieth century. A United Nations group has estimated that temperatures could rise one-point-four to five-point-eight degrees by the end of this century.



China Shipping

Another recent study looks at the importance of world trade in the production of carbon dioxide linked to climate change. This one is by two scientists at the National Center for Atmospheric Research in Boulder, Colorado.

Shui Bin and Robert Harriss wondered about the growth of the huge trade deficit the United States has with China. What if the United States had produced the goods itself instead of importing them? What effect would there have been on air pollution?


The findings suggest that in two thousand three, the United States would have released six percent more carbon dioxide. But China would have released fourteen percent less had it not made goods for the United States.

The two countries are the biggest producers of heat-trapping gases. The United States is estimated to produce about twenty-five percent of the world total. The scientists say China is responsible for about fifteen percent.

But, in general, China releases more industrial gases on average to make a product than the United States would. The scientists say this is because Chinese manufacturers depend more on coal and technologies that pollute more.


The scientists examined the growth of imports from China between nineteen ninety-seven and two thousand three. They estimate that the trade imbalance added seven hundred twenty million metric tons of carbon dioxide to the atmosphere. That was one percent of the combined amount released by the two nations during that period.

The study found that in two thousand two and two thousand three, releases of carbon dioxide grew eight to nine percent a year in China. In the United States, the rate was about one percent a year.

The scientists note that neither country has approved the Kyoto Protocol. That treaty aims to cut heat-trapping gases.

The National Science Foundation supported the research. The publication Energy Policy published the study online.

Shui Bin urged the United States to increase exports to China of technology for cleaner production. Not only could it help China reduces its pollution, she says. It could also improve the balance of trade between the two countries.


If you have a question about science, send it to special@voanews.com. Be sure to include your name and where you are from.

Or write to VOA Special English, Washington D.C., two-zero-two-three-seven, U.S.A. We might be able to answer your question on our show. But we cannot answer questions personally.

SCIENCE IN THE NEWS was written by Caty Weaver, Brianna Blake and George Grow. Cynthia Kirk was our producer. I’m Bob Doughty.


And I’m Pat Bodnar. Internet users can 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.