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EXPLORATIONS - June 5, 2002: Space Digest - 2002-06-03


This is Mary Tillotson.


And this is Steve Ember with the VOA Special English program EXPLORATIONS. We tell about an experiment in space that should answer a question. We report about NASA’s Cassini spacecraft that is on its way to Saturn. And we tell about the discovery of eleven more small moons that orbit the planet Jupiter.



A team of astronomers in Hawaii has discovered eleven more small moons that orbit the planet Jupiter. Thirty-nine moons now are known to orbit Jupiter. That is nine more moons than the planet Saturn has. For many years Saturn was thought to have more moons than any other planet. Thirty moons have been seen around it.

The University of Hawaii team leaders were Scott Sheppard and David Jewitt. Jan Kleyna of Cambridge University in Britain was also a member of the team. Mister Sheppard and Mister Jewitt have already discovered eleven other small moons in orbit around Jupiter. They made the earlier discovery in two-thousand.


The discovery team used a three-point-six meter telescope in Hawaii to make the latest discovery. This telescope is one of the largest electronic imaging cameras in the world. It is owned by Canada, France and the University of Hawaii.

The team of astronomers used the ability of the large telescope to gather images from a wide area around Jupiter. The team also used computers to search the images to confirm the orbits of suspected moons.

The computers rejected space rocks that may have been traveling through the area. The team used the University of Hawaii’s two-point-two meter telescope to continue to follow the orbits of suspected moons.


Robert Jacobson is a scientist with NASA’s Jet Propulsion Laboratory in Pasadena, California. Brian Marsden is a scientist with the combined research effort between Harvard University and the Smithsonian Institution. The two scientists say that all eleven of the moons travel in an orbit that is opposite to the direction that Jupiter turns.

The two scientists say these orbits are also very long and travel in many different directions. They said these unusual orbits are evidence that these small moons may have been large space rocks which were captured by Saturn’s gravity. They said the moons may have been captured when Saturn was first being formed as a planet.

Scientists have been discovering moons in orbit around Jupiter for almost four hundred years. The first moons of Jupiter to be discovered are the four largest. They were discovered in the year sixteen-ten by Italian scientist Galileo Galilei.



NASA reports that its Cassini spacecraft is in good condition and is speeding toward the planet Saturn. Cassini will arrive to begin orbiting Saturn on July first, two-thousand-four. The spacecraft was launched in October nineteen-ninety-seven. It has already traveled more than three-thousand-million kilometers toward Saturn.

Robert Mitchell is NASA’s manager for the Cassini-Huygens [HI-genz] program at the Jet Propulsion Laboratory in Pasadena, California. Mister Mitchell says the Cassini spacecraft has successfully completed a series of recent tests. These included test pictures taken of a star. The test was done to see if the camera could see clearly.

The extreme cold of space had fogged the lens the camera sees through so clear pictures were not possible. NASA corrected by problem by turning on heat devices built into the camera.

The cameras were warmed to a temperature just above freezing. Tests showed that more than ninety percent of the problem had been corrected. Another warming period was begun May Ninth to further correct the problem.


The Cassini spacecraft was named in honor of the Italian-French Astronomer Jean-Dominique Cassini. He was the scientist who first saw the famous rings that surround the planet Saturn. He discovered four of the planet’s moons in sixteen-seventy-five.

Cassini is an international project supported by the United States National Aeronautics and Space Administration, the European Space Agency, and the Italian Space Agency. Several European universities and major companies also are involved with the project.

Cassini carries the equipment needed to do twenty-seven scientific investigations of Saturn and its moons. The huge spacecraft weighs about five-thousand-three-hundred kilograms.


Cassini also carries a special device named for a Dutch scientist, Christiaan Huygens. He discovered Saturn’s largest moon, Titan. He lived and worked in the sixteen-hundreds.

The European Space Agency built the Huygens instrument. It will leave the Cassini spacecraft and parachute to the surface of Titan. It will take photographs, study the temperature and atmosphere and do other scientific tests of the moon. The Huygens landing device is one of the most important instruments on the Cassini project.

Scientists have been interested in Titan for a long time. Saturn’s moon Titan is about the same size as the planet Mercury. Scientists say Titan is extremely interesting because it has an atmosphere. It has the only other known atmosphere in our solar system besides that of Earth.


The flight of the Cassini spacecraft has been designed to gather large amounts of information about Saturn and its moons, and return this information to Earth. The information will include a study of Saturn’s atmosphere and its clouds.

The spacecraft will study the material found in Saturn’s rings. And it will study small particles collected by the spacecraft’s instruments.

NASA says the information gathered by Cassini will be added to what has been learned from past flights. This information will be used to plan flights far into the future.



We have a question for you today. When you plant a seed and it grows, how does the plant know which way is up? How does the top of the plant know to push its way through the dirt and into the sunlight?

How does the bottom of the plant know to grow down into the dirt? The question may sound funny, but scientists do not really know the answer. They do know that if you plant a seed up-side down, the plant will still grow in the correct direction.

Scientists also know that sunlight is not the answer. Trees in the far north still grow straight up, although the sun is never directly over them.

Scientists believe the pull of Earth’s gravity is involved somehow. Yet, they are not sure just what the pull of gravity does. They do not know how a plant can feel gravity.


Plant experts say they have two possible answers to the question. First, plant cells contain some fluid. The pull of Earth’s gravity may pull the fluid downward enough to cause pressure on the cell walls of a growing seed. This might serve as a sign that helps a plant decide which is up and which is down, and which direction to grow.

Scientists say another theory concerns the fact that all plants have a material called starch. They say the starch material may be pulled down by gravity.

Scientists do not know which of these answers is correct.


The question about how plants know which way to grow may be answered this summer during the flight of Space Shuttle Colombia. The Colombia is to be launched on July nineteenth, for a sixteen-day flight. It will carry a plant experiment to be done in the weightlessness of space. Scientists hope it will prove which theory is correct. The experiment will involve a common plant called flax.

Once in space, a computer-controlled amount of water will start the flax seeds growing. Unlike flax seeds growing on Earth, these seeds will not feel the pull of gravity. The water and the starch material in their cells will float rather than be pulled in any direction by gravity.

After the plants have been growing for awhile, astronauts will create a false gravity using special magnets. Scientists know this false gravity will affect only the starch material in the cells. It will not affect the water in the cells.


Karl Hasenstein is the top researcher for the experiment. He says the question will be answered by changing the gravity effect on the starch material. This will prove which one of the theories is correct. He says if the starch material theory is correct, the flax seed plants should start to grow in the direction of false gravity caused by the special magnets. If the way seeds grow is affected by gravity’s pull on the fluid in the cell walls, the magnets will have no affect.

We will report the results of the experiment in a future Explorations program.



This Special English program was written by Paul Thompson and produced by Cynthia Kirk. This is Steve Ember.


And this is Mary Tillotson. Join us again next week at this time for another EXPLORATIONS program on the Voice of America.