EXPLORATIONS - Space Digest（在线收听）

EXPLORATIONS - Space Digest
By Paul Thompson

Broadcast: Wednesday, March 17, 2004

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VOICE ONE:

This is Faith Lapidus.

VOICE TWO:

 
Mars and its polar caps.
And this is Steve Ember with EXPLORATIONS in VOA Special English. Today we tell about a new device to explore the polar areas of other planets. We tell about very distant solar systems photographed by the Hubble Space Telescope. We have news of a new comet that is moving toward Earth. We begin with the discovery that the planet Mars was once wet enough to support life.

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VOICE ONE:

On March third, scientists at the American space agency's Jet Propulsion Laboratory in Pasadena, California received exciting news from Mars.

The exploration device Opportunity sent back good evidence that liquid water once was an important part of the environment of Mars. NASA scientists said the evidence of water suggests that life may have once been possible on the red planet. This evidence was found near the place where Opportunity landed, known as the Meridiani Planum.

Steve Squyres is the top expert on the exploration rovers' science instruments. He says Opportunity has gathered enough good evidence to show there was once liquid water in the area being explored. Mister Squyres says liquid water flowed through the rocks that Opportunity studied. He said the water changed the chemistry of the rocks.

 
An image of microscopic minerals from Opportunity.
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Mister Squyres says this evidence includes minerals that form in the presence of water. Opportunity's drilling tool found the minerals when it dug two holes into rocks.

Tests show the rocks contained sulfur and salts in as much as forty percent of their material. Mister Squyres said this is extremely good evidence that the presence of water is strongly linked with these rocks.

He says there is enough evidence to suggest that it is possible that life could have existed in Meridiani Planum. However, he said Opportunity has not found any direct evidence to suggest that life was ever part of the Martian environment.

Mister Squyres says Opportunity is now examining rocks in the area to see how they were formed. He says they could have been laid down by minerals that came out of a mixture at the bottom of a salty lake or sea.

VOICE ONE:

Almost halfway around the red planet, the exploration vehicle Spirit has also found limited evidence of water in the Martian past. Spirit found some evidence of water in a rock at the Gusev Crater. Spirit used its drilling tool to explore the inside of a volcanic rock.

NASA scientists named the rock "Humphrey." It is about sixty centimeters tall. Researchers say the evidence of water found in Humphrey is far less than that found by the Opportunity rover.

The scientists want Spirit to explore other rocks for more and better evidence. Spirit will drill more deeply into rocks that have not yet been chosen.

 
An image of a crater called Bonneville from Spirit.
NASA scientists say both Opportunity and Spirit are returning extremely valuable information. The Spirit vehicle landed on Mars January third. It has been on the surface of the planet for seventy-five days. Opportunity landed about halfway around the planet from Spirit on January twenty-fifth. Both vehicles are expected to explore and carry out scientific tests for about ninety days.

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It is extremely difficult to design a vehicle that will be used to explore another planet. It is almost as difficult to test such a device here on Earth. However NASA has built and is testing a new device that may one day be used to explore the surface of some distant planet.

It is called the tumbleweed rover. The device is named after the tumbleweed, a large plant with a round shape. The plant dies and breaks loose from the ground. Then the wind blows it across the deserts of the American West.

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NASA's tumbleweed is a shaped like a large ball. It is almost two meters across. It carries scientific instruments. Scientists are developing the tumbleweed at NASA's Jet Propulsion Laboratory. They tested it in January at the National Science Foundation's Amundsen-Scott South Pole Station.

It rolled across Antarctica's polar area for eight days. Strong winds pushed the ball- shaped device across the ice at speeds as high as sixteen kilometers per hour. But sometimes there was no wind and the device did not move at all. It traveled about seventy kilometers during the test.

The average temperature outside was minus thirty degrees Celsius. However, the instruments inside the tumbleweed were kept at about thirty degrees Celsius.

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NASA researchers tested the tumbleweed rover in Antarctica because of the extremely cold temperatures there. They hope to use it to explore the polar areas of Mars and perhaps other planets.

Alberto Behar is a scientist working on the tumbleweed project. He says the device will be used to explore the polar areas of Mars for ice. Mister Behar says its instruments will measure air temperature, pressure, humidity and light and then transmit the information back to Earth.

Mister Behar says the ball shape of the device works well in polar areas. It will be able to use its instruments to find water beneath a desert or polar ice. He says scientists are developing an advanced tumbleweed rover at NASA's Jet Propulsion Laboratory in California.

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VOICE ONE:

A comet called C-Two-Thousand-Two-T-Seven is traveling toward Earth. You cannot see it yet unless you have a telescope. Even a small one will do. You can see the new comet near the planet Venus in the western part of the sky.

For the next three months, the comet will become brighter and brighter until a telescope is no longer needed. The comet will continue moving closer to Earth until May nineteenth. At that time it might be one of the brightest objects in the night sky. People in the Southern Hemisphere will be able to see it easily then.

If you have a telescope, now is the best time to see the comet in the Northern Hemisphere before it begins to move into the southern part of the sky.

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Another bright object in the night sky is the planet Jupiter. Jupiter recently moved closer to Earth, about six-hundred-million kilometers away. Jupiter will be very bright during this month. With a small telescope you can see four of Jupiter's many moons. You can easily see Jupiter in the eastern sky after sunset.

March is also a good month for seeing several other planets. Venus is the brightest. It can be seen early in the evening. It is easy to find and one of the brightest objects in the night sky. Between March twenty-fifth and March thirtieth, you will be able to see five planets in the early evening sky without a telescope. They are Mercury, Venus, Mars, Saturn and Jupiter.

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VOICE ONE:

NASA has released a series of photographs of objects that are farther away in the universe than anything seen before. The Hubble Space Telescope took the photographs during several months. The photographs include images of about ten-thousand galaxies.

NASA scientists say the photographs show galaxies of many ages and sizes, shapes and colors. They say the larger, brighter photographs show galaxies as they were more than one-thousand-million years ago. They say it has taken the light from these galaxies that long to reach an area of space where the Hubble Space Telescope could see it.

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The space telescope took the photographs from one very small area of the sky. Scientists chose this area because no stars or galaxies can be seen. The area appears to be empty if seen by telescopes from the ground.

Massimo Stiavelli is a researcher with the Space Telescope Science Institute in Baltimore, Maryland. He was the head of the project that took the photographs. Mister Stiavelli says the new Hubble photographs show an area of space that represents almost the very beginning of the universe.

Space scientists say the new photographs are very exciting. They say the photographs will lead to research that will offer new ideas about the birth and development of galaxies.

If you have a computer that can link with the Internet, you can see these beautiful and unusual photographs. Have your computer search for the word Hubble, HUBBLE, and follow the links.

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VOICE ONE:

This program was written by Paul Thompson. It was produced by Mario Ritter. This is Faith Lapidus.

VOICE TWO:

And this is Steve Ember. Join us again next week for another EXPLORATIONS program in VOA Special English.