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Monday, December 29, 1997 Published at 15:55 GMT

Special Report

The red planet: a year of discovery
image: [ Mars is much more like Earth than previously thought ]
Mars is much more like Earth than previously thought

On July 4 1997, after a voyage of nearly seven months, the Nasa spacecraft, Pathfinder, landed on the planet Mars.

It was the first mission to the red planet for more than 20 years. And it was the first time a roving vehicle had been sent to explore another planet.

The mission came at a time of renewed interest in Mars, after evidence emerged in 1996 suggesting that there might once have been life there. Some scientists believed that a meteorite found in Antarctica contained the fossilised remains of primitive life from Mars.

[ image: View of the planet's surface   NASA/JPL/Caltech]
View of the planet's surface NASA/JPL/Caltech
Although Pathfinder stopped sending information in October, possibly due to the hostile Martian climate, the mission was declared a resounding success.

Currently, a new probe is helping to unlock the secrets of Mars. Unlike Pathfinder though, Global Surveyor will not touch down on the planet. Instead, it is studying mars from orbit 235 miles above the surface as part of a two-year mapping mission.

In December 1998 and January 1999 Nasa plan to launch both a "lander" and an "orbiter" mission, under their Mars Surveyor Program. The aim is to bring back more information about the planet's surface.

Boost for space exploration

[ image: One day humans may stand on Mars and watch the sunset   NASA/JPL/Caltech]
One day humans may stand on Mars and watch the sunset NASA/JPL/Caltech
The Pathfinder Mission took seven months to the travel 497 million kilometres from the Earth to Mars, and cost a $150m dollars. But most importantly it landed safely -- four of the last six launches to Mars were lost.

A recent ill-fated attempt to investigate the planet was the Russian Mars-96 mission. Within hours of the launch, Russian television reported its failure after the rockets were unable to blast the craft out of its Earth orbit.

The success of the Pathfinder mission has provided a boost for space exploration and heralds a renaissance of flights to Mars.

The Pathfinder, now renamed the Carl Sagan Memorial Station, after the late US astronomer and writer, was so called because it was merely the first in a series of "low-cost" missions.

More are planned between now and 2005, when there will be a sample return mission - its aim is to physically bring a bit of Mars back to Earth. Scientists predict that people may well be on their way to Mars by 2015.

The planet has held a fascination for science fiction writers and scientists throughout the 20th century. Sixty years ago the radio play War of the Worlds caused widespread panic when it was broadcast in New York, detailing an invasion of the earth by Martians.

[ image: A computer graphic of Pathfinder landing on Mars, cushioned by airbags]
A computer graphic of Pathfinder landing on Mars, cushioned by airbags
But any future invasion is likely to be in the other direction. Matthew Gollenbeck from the American space agency, Nasa, said: "Mars is the most Earth-like of all the planets. It's the only other planet that has all the characteristics that are similar to those of the earth. It has an atmosphere; it has polar caps; it has a surface that rotates in 24 hours. It has all the elements we know that we need to support life. It's the only place that could be a future home for man."

Landing on an alien world

[ image: Scientists at mission control were overjoyed when Pathfinder landed safely]
Scientists at mission control were overjoyed when Pathfinder landed safely
Scientists at the Nasa Jet Propulsion Laboratory scarcely dared hope for success, but the Pathfinder had a textbook landing.

As it entered the atmosphere, special parachutes attached to the craft opened and the lander bounced to a standstill on giant airbags.

[ image: The pre-dawn Martian sky   NASA/JPL/Caltech]
The pre-dawn Martian sky NASA/JPL/Caltech
A few hours later, the sun rose over the Martian horizon, powering up solar cells so that the camera could begin sending pictures.

These revealed Pathfinder's little six-wheeled rover, Sojourner, ready to set out and analyse the rocks. They also relayed details of the Martian landscape -- the sand and boulders that surrounded the craft in the Ares Vallis plain, an area believed to have once been an enormous river.

In the distance there appeared to be hills, and on the horizon, great red mountain ranges. The surface of the planet is red because over billions of years it has become rusty as the iron minerals in the rocks oxidised.

Life on Mars?

[ image: The little roving vehicle named 'Sojourner' that gathered information on soil and rocks   NASA/JPL/Caltech]
The little roving vehicle named 'Sojourner' that gathered information on soil and rocks NASA/JPL/Caltech
The main aim of the Mars Pathfinder mission was to examine the surface and rocks of Mars. The question of whether there was once life on Mars will be answered in greater depth by future, possibly manned missions.

But as a result of the Pathfinder mission, scientists can now say that Mars is more like the Earth than previously thought, and it remains a possibility that there was once life there.

Mark Pine at Pathfinder Mission control said: "We have every reason to believe that at some point in the very distant past, billions of years ago, that water may have flowed freely on the surface of Mars and that raises obviously intriguing possibilities."

Where there was water there may also have been life.

Justin Mullins, technology editor of the New Scientist magazine, said: " We know that there was an atmosphere on Mars and we know it had weather systems, just like on earth. What it's telling us is that there was an enormous catastrophe on Mars that changed everything. Somehow atmosphere on Mars just leaked into space like a dripping tap and it ended up this barren frozen desert that we see now."

The rocks

[ image: Some of the rocks that the rover Sojourner analysed   NASA/JPL/Caltech]
Some of the rocks that the rover Sojourner analysed NASA/JPL/Caltech
Analysis of Barnacle Bill, the first rock to be encountered by Sojourner, showed that it shares similar properties with the Mars meteorite found in Antarctica.

Barnacle Bill was so-named because multi-coloured surface appeared to be spotted with what resembled barnacle shellfish.

Both rocks are thought to have come from the ancient Martian Highlands and Barnacle Bill may have been brought downstream by a river billions of years ago.

There is also evidence that Mars was subjected to much more volcanic activity than was previously thought. The mission scientists expected that most of the rocks would be igneous, that is formed by melting. But analysis from Barnacle Bill showed that it was a different type of volcanic rock called andacite, containing larger amounts of silica, which only forms after a long period of volcanic activity.

Martian conditions

Mars is a very cold world. It is about 50% further from the Sun than the Earth.

Even on the hottest summer day, the temperature does not really rise above the freezing point of water, so any water on Mars is permanently frozen in the ground.

In the winter, the temperature drops to below minus 100 degrees at the poles.

Mars is a a desert world. The air is incredibly thin - less than one hundredth of the pressure of the Earth's atmosphere. Humans would not be able to breathe on Mars because the atmosphere is made up of carbon dioxide.


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  Internet Links

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