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By Greg Clark
Arizona Daily Wildcat
September 19, 1997

UA scientists learning about Mars' geology


Photo courtesy NASA Jet Propulsion Laboratory
Arizona Daily Wildcat

The Mars Pathfinder as seen from Sojourner rover on the surface of Mars. Pathfinder sits on the deflated airbags that cushioned its landing on the martian surface. The rock in the foreground is pitted, possibly by the action of high winds.

Since landing on the red planet July 4, the Mars Pathfinder and its accompanying six-wheeled rover have been keeping UA scientists busy.

Eight scientists at the University of Arizona's Lunar and Planetary Laboratory are members of Pathfinder's imaging and science teams. During the past 11 weeks, they have been pouring over data coming down from the Martian landing site trying to decide just how the planet was formed.

"We're trying to systematically characterize the geology and processes that shaped the site," said Dan Britt, project manager for the Imager for Mars Pathfinder.

"We see a lot of different soil and rock types. We see bright red dust, darker lag deposits, even darker granular deposits and light colored patches, which may be chemically deposited hard-pan, similar to caliche," Britt said.

Evidence of floods, dust storms, volcanic activity and debris from impact craters also cover the site, said Peter Smith, director of the imaging team. Scientists are trying to determine which geologic processes shaped which surface features, he said.

Scientists are also attempting to discover the nature and origin of the Martian dust that gives the planet its characteristic red color.

The red dust, which is made of very fine particles about the size of talcum powder, may be a key to understanding the major processes that shaped Mars.

"With Pathfinder, we have a fairly good chance of unraveling what the Mars global dust is," Britt said.

"This dust may be wrapped up in very early formative processes at work 3 to 4 billion years ago," he said.

Britt and other team members are using spectral data from Pathfinder's camera and results of analysis by the Sojourner rover to determine the composition of the dust.

Another experiment attempting to analyze the magnetic properties of Martian dust may deliver significant results, Smith said.

Five small magnet arrays are placed at different points on the lander. The arrays are made up of magnets of varying magnetic strengths, attracting particles of differing magnetism. Depending on the magnetic properties of Martian dust, particles stick to different magnets, Smith said.

Looking at the dust collection patterns, scientists hope to determine the composition of the dust, he said.

Initial observations of the arrays suggest the dust is iron-oxide, or rust, but may be considerably different than the most common form of iron oxide found on Earth, Smith said.

"We are seeing patterns that indicate a mixture of hematite, which is the natural rust found on Earth, and maghemite, which is more strongly magnetic," Smith said.

"There are lots of different types of rust," Britt said. "We're trying to puzzle out exactly what rust processes are going on and what this holds for the past and present of Mars.

"If you have a process that requires a lot of water, then the inference is there was water in abundance when the rust was formed."

One of the great unanswered questions about Mars is what happened to the water. The Martian surface was shaped by massive floods, but now water only exists as polar ice and in minute amounts in the atmosphere, Smith said.

Analysis of soils and dust magnetism may lead to the missing water.

"We hope this tells us what happened to the water," Smith said. "It could be that all of it is chemically tied up in the soils."

Now scientists are interpreting data and arguing over differing interpretations.

Britt and others say there is enough data already to keep them busy well into next year, and Pathfinder data is still coming in.

"There needs to be a lot of debate," Smith said. "After a few years of debate and study there will be some consensus about the geological processes at work."

Pathfinder has performed beyond all realistic expectations, said Britt, surprising scientists at the amount and quality of data received, and the length of time it has been operating.

They now say Pathfinder may last until next summer, but eventually the extreme temperature variations will cause electronic circuits to fail.

A recent daily temperature peaked at 7 degrees Fahrenheit while the low fell to 109 degrees below zero.

Conditions for the lander and rover will only get worse, as Martian autumn is beginning at the landing site, the season when temperatures grow colder and severe dust storms begin, said Mark Lemmon, research associate at the Lunar and Planetary Lab and member of the imaging team.

"I think things will get more interesting because we are entering a period of seasonal weather changes," Lemmon said. "We've seen everything the way it is, and now we will get to see the site change."

In addition to rocky landscapes, Pathfinder's cameras have also taken pictures of clouds moving through the Martian atmosphere 10 to 15 kilometers (6 to 9 miles) above the planet's surface.

Scientists believe the clouds, which appear blue in a bright red sky, are made of crystals of water ice that condenses on dust particles in the atmosphere.

The motion of clouds have allowed scientists to measure atmospheric wind direction and speed, Lemmon said.


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