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Mars Once Had Moving Plates Like Earth Has Now
Written by Katherine Gypson, Cynthia Kirk and Karen Leggett
07 November 2005
This is SCIENCE IN THE NEWS in VOA Special English.
And I'm Bob Doughty.
I'm Faith Lapidus.
On our program this week -- new findings about Mars ...
A possible cause of prostate cancer ...
A new campaign to save children from AIDS, and a new kind of vaccine against polio.
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 (A) from observations by an American space vehicle, the
Mars Global Surveyor. The American space agency (B) 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 (1) an extended trip to gather more information.
The space agency says the new magnetic field map of Mars is (2) 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 (3) 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 mantle. As
the mantle rises up and breaks through the surface of the planet, the plates (B) 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 (C)
pushes from under the planet’s surface, building a new rock surface on top of the old.
Sometimes (4) different levels of rock will be pulled in different directions. This
happens when the magnetic field changes several times every million years.
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The planet Mars also has a series of mountains called the Tharsis volcanoes. They lie in
a straight line. (5) 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 volcanic 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 Canyon
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.
Comprehension Questions
1. What kind of a trip is it?
2. What does this mean?
3. Translate into Japanese.
4. How are the levels located with respect to the other levels?
5. What made the size so large?
Discussion Questions
6. What make(s) this map different from an ordinary map we are used to seeing?
7. What can you infer about Hawaiian volcanoes?
8. How was the surface created both for Mars and the Earth?
9. Do you think there are, or were, living organisms on Mars?
10. Do you want Martians, i.e. intelligent beings on Mars, to exist?
11. What do you or do you want to study at Kyoto University?
12. What are your plans after graduation?
Google の mailing list を教材配信に利用する事にしました。名前と所属と電話と
email を書いた email を僕に送って下さい。[email protected] です。既に Google
の会員の人も、上記が無いと mailing list (= Google group)に入れません。
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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 chromosomes that causes two
genes to combine, or fuse. This unusual gene 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 gland in men.
The researchers developed a step-by-step process for identifying genes commonly
linked to cancer. The process searches for unusual genetic 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 fusions 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
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reduce the need for such invasive methods.
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 hormone therapy.
The National Cancer Institute says more tissue studies are needed before new testing
methods or treatments can be developed.
The United Nations has launched a campaign to get countries to do more for children
affected 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 schooling 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.
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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.
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 vaccines.
They say it should now be used worldwide.
SCIENCE IN THE NEWS was written by Katherine Gypson, Karen Leggett and
Cynthia Kirk who was also our producer. I'm Bob Doughty.
And I'm Faith Lapidus. Our programs are online at voaspecialenglish.com. To send
us e-mail, write to [email protected]. Listen again next week for more news
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about science in Special English on the Voice of America.
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