What better way is there to prepare for a mission to Mars than to study a place with the same landforms and geologic features here on Earth?

Researchers from NASA's Jet Propulsion Laboratory, Arizona State University and the Lunar and Planetary Institute in Houston did just that this week when they surveyed a corner of central eastern Washington that resembles Ares Vallis, an ancient flood plain on Mars that will become the landing site for NASA's 1996 Mars Pathfinder lander and rover mission.

More than 60 scientists and educators gathered in the Channeled Scabland, near the cities of Spokane and Moses Lake, to examine landforms and geologic features created by one or more giant, catastrophic floods which swept through the area as the North American continent thawed from an ice age.

The field trip was designed to bring together Mars Pathfinder scientists and engineers, kindergarten through 12th grade educators from Washington and Idaho, and other interested members of the Mars scientific community. Eleven elementary and secondary school educators and five alternates were competitively selected in April to participate in the trip, based on their plans for educational follow-up activities involving students, teachers and parents in their home communities.

"The Scabland formed when waters the volume of Lake Erie and Lake Ontario combined broke through a glacial dam and flooded the region in about a two-week period," said Dr. Matthew Golombek, Pathfinder project scientist at JPL. "That flooding carved landforms and geologic features that are analogous to Ares Vallis."

The ice dam, located where present-day Lake Pend Oreille, Idaho rests, created Lake Missoula, Montana, which formed from the melting ice sheet that covered much of Canada during an ice age more than 15,000 years ago.

"We believe a catastrophic flood like this occurred in the Ares Vallis flood channel, washing rocks and sediments from highland regions into this flood basin early in Mars' history," Golombek said. "The two sites, in essence, are geologically analogous to one another."

The Mars Pathfinder landing site -- located at 19.5 degrees north latitude and 32.8 degrees west longitude -- is 850 kilometers (527 miles) southeast of the location of the Viking Lander 1, which in 1976 became the first spacecraft to land on Mars. Pathfinder will be the first spacecraft to land on Mars since the twin Viking landers arrived almost 20 years ago. Scheduled to arrive on July 4, 1997, Pathfinder will parachute down to Ares Vallis at the mouth of this ancient outflow channel, which was chosen for the variety of rocks and soil samples it is thought to contain.

"The Ares Vallis site is what we call a 'grab bag' location with a wide variety of rocks that were swept into the area during this catastrophic flood," Golombek said. "The plain is most likely made up of a thin veneer, perhaps 100 meters thick, of flood deposits. Using a microrover, we hope to sample a wide variety of rock types and ages within a 10-meter (33-foot) radius of the lander."

Both the Pathfinder lander and rover will carry stereo imaging systems to photograph the Martian terrain. The rover will also be equipped with an alpha proton x-ray spectrometer, which will allow scientists to examine the composition of the rocks. The imaging system will reveal the mineralogy of surface materials as well as the geologic processes and surface atmosphere interactions that created and modified the Martian surface. The instrument package will also yield information on dust particle size and water vapor abundance in the thin Martian atmosphere.

Even though the exact origins of the rock samples on Mars will not be known, the chance of sampling them could reveal a lot about the planet, Golombek added. The rocks would have been washed down from highlands at a time when floods moved over the surface of Mars, telling scientists much more about Mars' early evolution.

"Viewing the Scablands on this trip allowed engineers designing the Pathfinder lander and rover to become familiar with the kinds of surfaces the lander must land safely on and the rover must roll over during the Pathfinder mission," Golombek said. "The educators were particularly excited at being a part of the discussions between the Mars scientists and Pathfinder engineers about the nature of the landing site."

In addition to bus trips to the Scabland site, participants also saw the region from the air. Flights over the flood plain gave them aerial panoramas of the outflow channel so that they could better understand the full context and history of these immense landforms produced by the Lake Missoula floods.

"The intuitive understanding gained by seeing the Scabland terrain from both the air and ground will be essential for interpreting the nature of the Mars Pathfinder landing site in Ares Vallis," Golombek said. "The relevance to Ares Vallis is especially important because Pathfinder will not obtain descent images on the way down. We'll have to rely on existing Viking images and images taken from the Pathfinder lander once its on the ground to interpret the geological context of the landing site."

The Scabland field trip was co-sponsored by Arizona State University, NASA's Jet Propulsion Laboratory, and the Lunar and Planetary Institute in Houston. Mars Pathfinder -- the first of NASA's Discovery missions -- is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, D.C.

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