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Mars Pathfinder

written by Jeff Harr on December 13, 2000
number of views: 76960 |   printable version (text) (PDF)

Sojourner Rover
Sojourner Rover
Credit: NASA
The metallic voice counts down....5....4....3....2....1. The ground begins to shake. And with a surge of raw power, the blue and white Delta II takes off into the sky, carrying with it the hope of mankind in their efforts to learn about the red planet. This was much the scene on December 4th, 1996, the date that the Mars Pathfinder's journey towards the barren surface of Mars began. Its approximately 6 month journey took it on a spiral around the Earth, with the gravitational pull slinging it towards its final destination, Ares Vallis (a giant outflow channel).

The mission was another example of NASA's new motto, "faster, better, and cheaper", especially cheaper, at 1/5 the Viking's price tag. It also was the first mission to employ a microrover, (basically a remote controlled robot resembling an RC car). The Pathfinder is equipped with state of the art scientific equipment, in order for it to gather as much information as it can. These apparatus include the Microrover (named Sojourner), the IMP (or Imager for Mars Pathfinder), the Alpha Proton X-Ray Spectrometer (Whew!), and the Atmospheric Structure Instrument/Meteorology Package. These instruments, combined with the cameras and radios of Pathfinder, uncovered a great deal of heretofore unknown data.

Pathfinder's lander and Sojourner exceeded expectations, outlasting forecasts three and twelve times respectively. Since its landing on July 4, 1997, Mars Pathfinder has returned the following:

-2.6 billion bits of information -more than 16,000 images of Mars and the landing site -more than 15 chemical analyses of rocks -data on winds and weather

Dr. David Baltimore, president of the California Institute of Technology, summed up the projects success with this statement, "This mission has advanced our knowledge of Mars tremendously and will surely be a beacon of success for upcoming missions to the red planet."

Sojourner Rover

The Rover (which is basically a robot that can drive around the planetary surface), was a vital part of the Pathfinder mission. Christened Sojourner, the little rover carried a variety of equipment to help analyze the Martian surface, including the APXS system. Its mission included analyzing rocks in a 10 meter circle around Pathfinder. The Rover's wheels were designed with steel treads and cleats to help it clear the rocky terrain. Its speed was not very impressive (only .6 meters per minute). To prevent the little rover from tipping over, it was equipped with motion sensors on its frame that analyzed tilt. The rover took many images of the surface, and the rocks that it had analyzed, sending them back to Earth along with scientific data.

A previous try at the rover idea was made by the Russians in 1970. Called the Lunakhod 1, it was landed on the moon and took more than 20,000 images.

The Sojourner rover was the first to actually be operated on another planet. The Rover's operations included taking images each sol to determine the operations for the next sol, to take and analyze soil samples, imaging the pathfinder lander to help with engineering assessment, and conducting a series of experiments to validate the rover idea. It's every move was tracked during its time on Mars, including images of every trench its wheels created, thermal monitoring, logging of vehicle performance data, and records of sensor performance. The mission was a guideline for future rover based missions and helped us better understand the Red Planet itself. risk to human explorers.

Scientific Results

Geology - The cameras onboard Pathfinder took images which were used to create composites back on Earth. These images revealed a rocky plain theorized to have been formed by catastrophic floods. The findings conclude that Mars was more Earth like than previously believed. There is major evidence of a water covered planet sometime in Mars' ancient past. However, because of the lack of erosion, the presence of water is impossible before 1.8 billion years ago.

Minerology - The Alpha Proton X-Ray Spectrometer was used on nine separate specimens of rock, to find their composition and properties. They turned out to be rocks formed in the partial melting of Mars' upper mantle. Geologists expected to find mainly basalts on the red planet, but they were surprised when pathfinder turned up andesites, high in silicon content. This could mean that the crust composition of present day Earth and ancient Mars were very similar. Another surprise was that not all of the rocks analyzed were volcanic. Some may have been sedimentary, with striations characteristic of water deposited sediment.

Soil - The soils at the landing site had a lower silicon content than the rocks, and varied in color from bright red dust to gray. The scientists believe that the soil is globally constant, due to the fact that the soil around Viking (on the other side of the planet) is very similar. An unknown pinkish-red material also covered the landing site.

Meteorology and Atmosphere - Due to dust in the atmosphere, the sky has a pink hue, the same as when Viking landed. The combination of dust in the atmosphere and a miniscule amount of water vapor make Mars worse than an Earthly desert. Temperature ranged from -10 degrees Celsius to -76 degrees celsius. This is roughly the temperature of a very very cold day in Alaska. An interesting observation was the change in air pressure during the seasons. In the wintertime on mars, the entire atmosphere at the poles freezes into a solid pile of carbon dioxide.

Magnetic Properties - The Pathfinder team was clever in their magnetic testing device. The Pathfinder was speckled with magnetic points which were observed for deposits by sensors. The tests concluded that the dust in the atmosphere is highly magnetic. This is due to a material called maghemite, another consistency with a watery past.

Rotation - The scientists got a little extra out of Pathfinder. They were able to use Doppler tracking to conclude that the tilt of mars has changed since 20 years ago, at the time of the last Viking reading. This will permit scientists to revise their calculations, and in turn, help determine the secrets of Mars' past.

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