SCIENCE IN THE NEWS - Mars Once Had Moving Plates Like Earth

（单词翻译）

SCIENCE IN THE NEWS - Mars Once Had Moving Plates Like Earth Has Now
By Katherine Gypson, Cynthia Kirk and Karen Leggett

Broadcast: Tuesday, November 08, 2005

(MUSIC)

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Faith Lapidus.

VOICE TWO:

And I'm Bob Doughty¹. On our program this week -- new findings about Mars ...

VOICE ONE:

A possible cause of prostate cancer ...

VOICE TWO:

A new campaign to save children from AIDS, and a new kind of vaccine² against polio.

(MUSIC)

VOICE ONE:

American scientists have found evidence that the surface of the planet Mars once moved like that of present-day Earth. The evidence comes from a new map of magnetic forces on Mars.

 
 
The map was put together from observations by an American space vehicle, the Mars Global Surveyor. The American space agency sent the Mars Global Surveyor into orbit around Mars in nineteen ninety-seven. The spacecraft spent nearly four years studying the planet, its atmosphere and what lies under its surface. The spacecraft is now on an extended trip to gather more information.

VOICE TWO:

The space agency says the new magnetic field map of Mars is the first of its kind. The map provides images of the full surface of the planet.

Scientists say the map shows that the surface of Mars was created in much the same way as Earth's. On both planets, the outer surface is broken up into large pieces, or plates. These plates are moving over areas of hot liquid rock, called the mantle³. As the mantle rises up and breaks through the surface of the planet, the plates push apart. The mantle reaches the surface and cools into hard rock.

The magnetic field on the planet pulls the rock in one direction. More material pushes from under the planet's surface, building a new rock surface on top of the old. Sometimes different levels of rock will be pulled in different directions. This happens when the magnetic field changes several times every million years.

VOICE ONE:

The planet Mars also has a series of mountains called the Tharsis volcanoes. They lie in a straight line. Volcanoes on Mars are ten to a hundred times larger than those on Earth. Scientists have wondered why this is so. With the help of the map, scientists can now see that the mountains were formed in a very hot area between two plates. On Earth, this kind of volcanic⁴ activity formed the Hawaiian Islands.

The Mars Global Surveyor also examined an extremely deep hole. It is called the Valley Marineris. It is six times as long and eight times as deep as the Grand Canyon⁵ in the western United States.

The spacecraft also found that the magnetic field on Mars did not cover the planet. Magnetic fields protect planets from some kinds of radiation from space. Scientists think the presence of even a partial magnetic field around Mars may mean that living organisms were able to exist on the planet.

(MUSIC)

VOICE TWO:

You are listening to SCIENCE IN THE NEWS in VOA Special English, from Washington.

Medical researchers may have found a cause of prostate cancer. They say the finding could lead to more effective treatments and a possible cure for the disease.

The researchers said they identified a way of organizing chromosomes⁶ that causes two genes⁸ to combine, or fuse. This unusual gene⁷ activity is found only in prostate cancer. The researchers said they found the gene activity in most of the prostate cancer tissue they studied. The genes did not combine in prostate tissue free of the disease.

Arul Chinnaiyan of the University of Michigan Medical School led the study. The research team included scientists from the United States and Germany. Science magazine reported their findings. America's National Cancer Institute provided support for the study.

The two genes involved are called ETV-One and ERG. They are normally separate. But each fused with another gene, known as TMPRSS-Two. This gene is directly linked to the prostate gland⁹ in men.

VOICE ONE:

The researchers developed a step-by-step process for identifying genes commonly linked to cancer. The process searches for unusual genetic¹⁰ activity in prostate cancer tissues.

Laboratories at the University of Michigan tested twenty-two pieces of prostate cancer tissue. The process found the unusual gene activity in ninety-one percent of the tissue studied.

No one knows what caused the genes to fuse. Researchers say similar gene fusions¹¹ are likely to be seen in most prostate cancers. But they say other unknown gene combinations may be the cause for the other prostate cancers.

The presence of these gene combinations may one day be used to test for prostate cancer. Doctors now test men for levels of prostate-specific antigen, or P.S.A. P.S.A. is found in the blood or liquid wastes. But experts say P.S.A. tests are not always dependable. Doctors often need tissue to confirm prostate cancer. Experts say better tests would reduce the need for such invasive methods.

VOICE TWO:

Prostate cancer is the most common cancer for men in the United States. The American Cancer Society says more than two hundred thousand new cases will be reported this year. The group says more than thirty thousand people will die from it.

Prostate cancer is the second most common cause of cancer-linked deaths among men. Men over fifty years old are at greater risk, as are those with a family history of the disease.

Most prostate cancers grow very slowly and never appear to spread. But some can grow and spread quickly. Treatments include removal of part or all of the prostate, radiation and hormone¹² therapy.

The National Cancer Institute says more tissue studies are needed before new testing methods or treatments can be developed.

(MUSIC)

VOICE ONE:

The United Nations has launched a campaign to get countries to do more for children affected¹³ by H.I.V. and AIDS. The U.N. Children's Fund and the U.N. AIDS program call their campaign, "Unite for Children. United Against AIDS."

AIDS resulted in three million deaths in two thousand four. One in six victims was under the age of fifteen.

But UNICEF says millions of children are affected by AIDS even if they are not infected with the virus that causes it. Many lose parents or brothers and sisters. In some cases, they are even denied schooling¹⁴ and health care just because of their family situation.

U.N. officials say about fifteen million children have lost at least one parent because of AIDS. Yet, they say, less than ten percent of these children receive any public support or services.

Southern Africa is home to almost ninety percent of children infected with H.I.V. But the virus is increasingly spreading among young people in Asia and eastern Europe.

VOICE TWO:

About half of all new H.I.V. infections worldwide are among people age fifteen to twenty-four. UNICEF aims to reduce new infections among young people by twenty-five percent within the next five years.

Less than five percent of children with H.I.V. receive treatment now. UNICEF wants to increase that number, and also services for pregnant women to prevent infection of their babies.

The campaign aims to reach eighty percent of children most in need of services by two thousand ten.

(MUSIC)

VOICE ONE:

A new kind of vaccine is being used to stop the spread of polio. World health officials say the vaccine is an important tool for the final part of the campaign to end the disease.

Experts recently met in Geneva to discuss the progress. They say polio could be gone within six months everywhere except Nigeria, which has the most new cases. The experts say at least another year of work is needed there.

Doctor Steven Cochi [KAH-chee] is with the United States Centers for Disease Control and Prevention. He says, "There is no reason why polio should continue to exist anywhere in the world after next year."

Until now, the vaccine used to prevent polio has combined three different medicines. That is because there are three different polio viruses. But only two of them still exist: type one and type three. Type three exists in parts of Nigeria, Afghanistan and India. Type one is more common.

The recently developed vaccine is known as monovalent oral polio vaccine. It protects only against the type one virus. World health officials say it appears to work faster than existing vaccines¹⁵. They say it should now be used worldwide.

(MUSIC)

VOICE TWO:

SCIENCE IN THE NEWS was written by Katherine Gypson, Karen Leggett and Cynthia Kirk who was also our producer. I'm Bob Doughty.

VOICE ONE:

And I'm Faith Lapidus. Our programs are online at www.tingroom.com. To send us e-mail, write to [email protected]. Listen again next week for more news about science in Special English on the Voice of America.