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This is SCIENCE IN THE NEWS in VOA Special English. I'm Steve Ember.

VOICE TWO:

And I'm Shirley Griffith. This week, we will tell about evidence that something big struck the planet Jupiter. We will also tell about a long ignored organ in the body. And we will tell how scientists are using lobsters to help protect the sea environment.

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Jupiter's new spotSpace discoveries are usually made by scientists whose job is to study astronomy. After all, they observe the skies with huge ground-based and costly space telescopes. But last month, a computer programmer from Australia made an exciting discovery of an unusual event in Earth's solar system.

Anthony Wesley found an unusual dark marking in Jupiter's atmosphere using his amateur telescope. Operators of the Hubble Space Telescope said the dark spot is about two times the length of the United States. Scientists believe it is evidence that a large object struck Jupiter, cutting a hole in the atmosphere of the huge, gaseous planet.

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Mister Wesley saw the spot near Jupiter's extreme south on July nineteenth. At first, he thought it was the shadow of one of Jupiter's four big moons. He captured images of the spot and studied a picture that he had taken earlier of the same area on Jupiter.

When Mister Wesley was sure he had found something new, he quickly contacted professional astronomers about his find. Leigh Fletcher and Glenn Orton were among the first people he told of the discovery. They work for the American space agency's Jet Propulsion Laboratory in California.

The Americans had planned to use the Infrared Telescope Facility on top of Hawaii's Mauna Kea volcano the following night. When they used the telescope to create images of the planet, they found an area that appeared dark in light the human eye could see. But using infrared light, the spot appeared bright. That is because the force of the object hitting Jupiter pushed very reflective particles high into the planet's atmosphere.

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Astronomers may never know exactly what struck Jupiter. The incident probably took place within a day or two of Mister Wesley's observation. But scientists think it was either a comet or rock from space.

Reports of solar system objects striking each other are extremely rare. But astronomers have seen a similar collision. It took place exactly fifteen years ago. Comet Shoemaker-Levy Nine broke up and struck Jupiter.

In that event, astronomers were able to observe the icy comet long before it struck the solar system's biggest planet. But the object that struck Jupiter in July is estimated to have been much smaller and harder to see than comet Shoemaker-Levy. Astronomers say it was probably less than one kilometer in size -- too small to see from Earth.

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This most recent collision with Jupiter brought attention to how the huge planet's gravity affects our solar system. Some scientists have called Jupiter the protector of the inner planets -- and our own Earth -- from objects from the outer solar system. But others note that Jupiter's powerful gravitational field can just as easily send an object into Earth's path as push it deeper into space.

Frank Marchis is an astronomer with the University of California at Berkeley. He says the surprise collision clearly justifies the need for programs that search the skies for small space objects that could threaten earth.

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The spleen was once known in western literature as an organ that caused a person to be sleepless and sad. For example, in his poem "Spleen," the nineteenth century French writer Charles Baudelaire describes a cheerless world where nothing is beautiful.

For years, the duties of the spleen were generally not considered very important. In fact, a person whose spleen has been damaged can survive without it. People who suffer severe physical injuries can burst their spleen and have it removed by doctors.

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SpleenThe human spleen is an organ about the size of a closed hand. It is above the stomach, under the ribs on a person's left side. The spleen is part of the body's lymphatic system. This system fights infection and helps keep the body's fluids in balance.

A recent report shows that the small organ has a much more important job in the body's defense system than once believed. Researchers at Massachusetts General Hospital and Harvard Medical School wrote the report. It shows that the spleen stores huge numbers of white blood cells called monocytes.

Masses of these monocytes leave the spleen in the event of an injury like a heart attack, wound, or infection. They gather in the damaged tissue and help it to heal.

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Matthias Nahrendorf helped to write the report in Science magazine. He describes the monocytes in terms of military language. He says they are like a standing army that you only deploy in times of crisis.

Researchers have long known that bone marrow produces and contains monocytes. But the writers of the report knew that the number of monocytes in the blood stream was too low to explain the millions of them present after an injury to the heart. They discovered that the additional monocytes were coming from the spleen.

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The researchers used mice to carry out an experiment. They studied what areas of the spleen store the monocytes. And they gave the mice heart attacks to study the deployment of monocytes from the spleen.

This information about the spleen brings new meaning to a report published in nineteen seventy-seven. At that time, researchers studied more than seven hundred American soldiers who had had their spleens removed because of battle injuries. They also studied a similar sized group of soldiers who had suffered injuries but kept their spleens. The soldiers without spleens were two times as likely to die of heart disease as the soldiers who still had their spleens.

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Kelp is a form of large, brown seaweed. It grows in watery forests in a number of areas.

Kelp forests provide a protected home and food for many kinds of sea life. Scientists once thought that these forests existed only in moderate and cold climates. Two years ago, however, they were also found in warm ocean waters near Ecuador.

Finding kelp forests is usually a welcome discovery. Some economies depend on fishing for lobsters, rockfish or other creatures that need the forests. People harvest kelp to get alginic acid. The substance is used in toothpaste and medicine for stomach problems. And people active in water-sports like to dive and row boats in kelp forests.

A researcher measuring a spiny lobsterVOICE TWO:

However, a small, colorful creature called the long-spined sea urchin is destroying kelp in some areas. The urchin is shaped like a ball. It also has sharp, finger-like spines.

For example, urchins are ruining coral reefs in waters near Australia. Scientists at the University of Tasmania say the urchins are wrecking areas in which many fish and shellfish grow. The scientists say abalone and lobsters are among the urchins' victims.

But the lobsters are fighting back. The scientists say seven hundred fifty large rock lobsters were released a year ago in waters near Tasmania's northeast coast. University of Tasmania scientist Scott Ling says there is evidence that they have been eating the sea urchins.

More lobsters are being placed in waters that scientists consider at high risk in Tasmania's southeast. Mister Ling says the hope is that they will prevent further development of sea urchins.

The lobsters are identified with markers and colored dye so fishermen will not catch them. And the fishermen are said to be cooperating.

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The American state of California is another area where long-spined sea urchins have been destroying kelp forests. Southern California has lost ninety percent of its watery forests since the nineteen sixties. The state has employed divers to remove urchins along its southern coast. They are being moved to a new home about one and one half kilometers away. The job is not easy. Currents are strong and the creatures sometimes cut the skin of the divers.

But the diving team has been doing its work two times a week. On one recent day, one thousand five hundred sea urchins got a new home in deeper water. And many kelp forests now have a more secure future.

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VOICE TWO:

This SCIENCE IN THE NEWS was written by Dana Demange, Mario Ritter and Jerilyn Watson. Our producer was Brianna Blake. I'm Shirley Griffith.

VOICE ONE:

And I'm Steve Ember. Listen again next week for more news about science in Special English on the Voice of America.