This is Shirley Griffith.
And this is Steve Ember with EXPLORATIONS in VOA Special English. Today we complete our two programs about exploring the planet Mars. We tell about the two vehicles that have landed successfully on the Red Planet and are exploring the surface for evidence of water and life.
People on Earth have always been interested in the planet Mars. Recently, that interest has increased because several successful spacecraft have been placed in orbit around Mars. These include the American space agency's Mars Global Surveyor and Mars Odyssey and the European Space Agency's Mars Express.
Each of these spacecraft has increased our knowledge of Mars. Each has sent back huge amounts of scientific information and photographs of the planet. The National Aeronautics and Space Administration has given that information and photographs to the public on the Internet computer system. This too has increased public interest in Mars.
Perhaps the most exciting event took place on January third. That is when the first of two Mars exploration vehicles successfully landed on the Red Planet. The first lander is named "Spirit." It came to rest in an area of Mars named Gusev Crater. Millions of people used their computers to link with NASA's Internet Web site to see photographs sent back by Spirit.
On January fifteenth, NASA scientists told Spirit to use its six wheels to move off the landing device. It did this successfully and rolled on to the surface of Mars. Excited NASA officials said Spirit was now ready to begin its task of exploring the surface of the Red Planet.
Scientists on Earth sent commands to have Spirit move to a rock that could be clearly seen in photographs. It did this successfully. Spirit continued to send back photographs and valuable information.
On January twentieth, scientists told the exploration rover to use one of its tools to study the soil near the rock. The next day, Spirit began having problems. It answered radio signals, but it would not send back scientific information.
NASA officials began to work to correct the problem with Spirit's computer. The part of the computer that stores information was not working correctly. On February first, NASA announced that Spirit's computer memory had been successfully repaired. It will begin scientific examinations of rocks later this week.
On January twenty-fourth, the second rover device reached the surface of Mars. It too immediately began sending back photographs of a very different area of Mars. Public interest in Mars increased again.
The second vehicle is named "Opportunity." It landed in an area of Mars called Meridiani Planum. NASA scientists say Opportunity landed inside a large hole in the surface of the planet.
Photographs from Opportunity show several large formations of rock. The photographs clearly show this rock is below the surface. NASA scientists say the rock they see in the photographs is not like anything they have ever seen before.
On January thirty-first, Opportunity moved off its landing device and on to the surface of Mars. NASA officials say it will examine soil in front of it for the next several days.
Steve Squyres is a scientist at Cornell University in Ithaca, New York. He is the chief investigator for science instruments on both Opportunity and Spirit. He says the areas where the two devices landed are very different. He says Opportunity landed in a very strange and wonderful area for scientific investigation.
He says that scientists are extremely excited about the Meridiani Planum area. Mister Squyres says it is good that Opportunity landed in a hole. It will be able to explore areas below the surface of the planet without having to dig.
He also says the hole is not deep. This means when Opportunity is done exploring this important area it will be able to drive out of the hole with little or no problems. It will then be free to explore other areas.
NASA officials say they have discovered and confirmed that Opportunity landed on an area of Mars that is rich in the mineral crystalline hematite. On Earth such hematite usually forms in the presence of water. Scientists want to know if the hematite on Mars was formed under water too.
Some evidence suggests that long ago the Meridiani Planum area of Mars was wet and held water. Opportunity will search for more evidence of water and any evidence that some kind of life could have existed in the area.
The Meridiani Planum where Opportunity landed and Gusev Crater where Spirit came to rest are very different. They were both carefully chosen from among one-hundred-fifty areas on Mars.
NASA officials were able to make the choice using photographs and information supplied by the Mars Global Surveyor and Mars Odyssey spacecraft. Both are in orbit around the planet.
The Spirit and Opportunity exploration vehicles carry special scientific equipment to learn many of the secrets of Mars. Both vehicles are exactly the same. Each weighs one-hundred-seventy-four kilograms. Each carries several cameras. But the cameras are used for different purposes.
One camera is used to see where the vehicle is going. It searches for a clear path that is free of major objects.
Another camera takes extremely detailed color photographs. It can take photographs in a complete circle around the exploration vehicle. One camera is inside a microscope that can see objects as small as a human hair.
Batteries provide power for the exploration rovers. The batteries store power they receive from special solar collectors that change sunlight into electric energy.
The exploration rovers carry communications equipment that permits them to communicate directly with Earth. They can also communicate with the Mars Global Surveyor satellite in orbit around the planet. The Surveyor satellite can pass on information it receives from the rovers.
Each rover carries a special computer that can survive in the extremely cold temperature of Mars. The computers can also survive extreme amounts of radiation.
The rovers each carry a science instrument called the Alpha Particle X-Ray Spectrometer. This instrument can be placed on rocks and soil to study the chemicals inside.
Another tool is called the Thermal Emissions Spectrometer. This tool studies minerals in rocks and soil from a distance by measuring the amount of heat radiation they release. It can also study the planet's atmosphere.
Devices called Capture-Filter Magnets can capture and hold dust that contains small amounts of iron. The other scientific instruments can then study this dust.
One of those instruments is the Mossbauer Spectrometer. This instrument is designed to study minerals that have large amounts of iron.
Spirit and Opportunity each carry a Rock Abrasion Tool. This is a powerful machine that uses electric motors to grind away the surface of rocks so the inside material can be inspected and studied. This is done with the microscope camera and other scientific instruments.
Mister Squyres says all of the science instruments make the two vehicles into mechanical scientists. He says they use their color cameras and infrared instruments to study rocks and interesting soil at a distance. The vehicles then are commanded to go to the rocks or areas of soil that seem most interesting.
When they get to an interesting area they reach out with a mechanical arm that carries several tools. The arm carries the microscope, two instruments for identifying what the rock is made of and a tool for cutting into the rock.
Scientists say that Spirit and Opportunity will explore the surface of Mars for as long as ninety days. The rovers will be exploring the surface in an effort to find evidence of water on Mars. Water is extremely important to any future human exploration of Mars.
The two devices are trying to discover if we have not been alone in the universe. They are trying to answer the question: Is there any evidence that life once existed on the Red Planet?
This Special English program was written by Paul Thompson. It was produced by Mario Ritter. This is Steve Ember.
And this is Shirley Griffith. Join us again next week for another EXPLORATIONS program on the VOICE OF AMERICA.