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Mission to Mars: Geologists on six wheels

By PHIL BERARDELLI, United Press International   |   Jan. 8, 2004 at 8:32 AM   |   Comments

Part 3 in a series by UPI examining ongoing attempts by humans to explore the surface of Earth's nearest planetary neighbor.

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WASHINGTON, Jan. 7 (UPI) -- In July and September of 1976, the twin Viking landers set down on the surface of Mars, scooped up a few handfuls of soil, took reasonably detailed color photographs of the planet's landscape, and captivated millions of earthbound viewers.

More than two decades later, in the summer of 1997, the tiny Sojourner rover rolled only a few feet from its parent, the Pathfinder lander, examined a few nearby rocks and likewise generated oohs and ahs as an appreciative humanity looked on.

Now, in the coming weeks, the latest visitors to the red planet -- NASA's twin Mars Exploration Rovers, named Spirit and Opportunity -- should easily surpass those accomplishments as they roam hundreds of yards from their respective landing sites and provide unprecedented views of the Martian terrain.

MER mission scientists liken Spirit, which landed successfully on Jan. 3, and Opportunity, which is due to set down on Jan. 25, to planetary geologists on six wheels. The rovers, which cost a combined $820 million, represent the most advanced technology available for interplanetary exploration.

"You have to understand, this will be a dramatic, dramatic improvement" over the previous landers, said MER team member Matt Golombek, of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Where the Vikings and Pathfinder/Sojourner basically stayed in one place, Spirit and Opportunity "will acquire multiple panoramas," he said.

The complexity of the rovers and the challenges of their mission are why JPL scientists may not order them to go mobile for up to two weeks after landing. For one thing, the rovers were packed in a crouched, intricate, origami-like arrangement within their landing packages. Unfolding each MER's camera mast, robot arm, radio antennas, solar panels and wheels is a delicate, time-consuming operation.

For another, the Spirit and Opportunity teams will be in communication with their rovers only for about one hour each day. Within that time, they must transmit the day's orders and retrieve the previous day's data. After that, each mission team interprets the data and attempts to reach a consensus about what to order its respective rover to do tomorrow, while the craft is on its own for the remainder of the 24-hour, 40-minute Martian day.

During the daylight part of that time -- a necessity because the MERs are solar-powered, with back-up batteries used only for data storage and heating critical spacecraft components -- each rover will either move toward the next targeted object in its vicinity or bring its sophisticated instruments to bear on a Martian rock.

"The most interesting targets are the rocks," Golombek said. They carry the geologic record of the planet and the rovers are equipped to tease out their secrets, using an array of exquisitely sensitive instruments.

For example, Spirit and Opportunity are expected to transmit thousands of high-resolution, color, stereoscopic images of their surroundings, using cameras with three times the resolution of Pathfinder's, said MER team member Joy Crisp. "Their resolution rivals the human eye," she said.

The rovers also will monitor the chemical composition of the Martian atmosphere using a thermal emission spectrometer, or TES, with a resolving capability equivalent to the optical cameras.

Whenever mission scientists identify a particularly interesting rock, they will order the MER to deploy the instrument they call the RAT, for rock abrasion tool. Located on a robot arm, the diamond-impregnated RAT will grind off the rock's weathered surface, revealing its pristine interior. Then the arm will analyze the new surface with its microscopic imager -- a miniature version of the twin panoramic cameras designed for extreme close-up views -- an alpha particle X-ray spectrometer to determine basic chemistry, and a Mossbauer spectrometer to analyze iron content.

For three months -- their estimated operational lifetimes -- will repeat this process many times. Though slow-moving -- their top speed is only about 10 feet per minute on flat, hard ground -- the golf-cart-sized rovers are nimble. They are capable of rolling over rocks nearly the size of Sojourner, using a rocker-bogie suspension system that bends at the joints. The rovers also carry navigation and hazard-avoidance software to help them navigate their own way toward targeted objects.

All these capabilities should become apparent in the coming weeks, if all goes as planned. Meanwhile, Spirit already has thrilled its mission team and other observers by transmitting the highest-resolution pictures ever sent from Mars on Tuesday. Spirit's panoramic camera took 12 contiguous frames that the camera team combined into the mosaic.

"This is the day we've been waiting for," said Cornell's Jim Bell, leader of the panoramic camera team.

"There are places where rocks were dragged through the soil and the soil was stripped off and folded into bizarre textures," Bell said. Other areas show tails of debris to one side of rocks, possibly shaped by Martian winds. "There's a wonderful mix of both smooth and angular rocks near the landing site, and this is something we'll be trying to puzzle out in the next few weeks," he added.

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Next: Reading the rocks

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Phil Berardelli is UPI's Science & Technology editor. E-mail sciencemail@upi.com

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(Editors: UPI photos WAS2004010651, WAS2300312302, WAS2300312305, WAS2300312306 and WAS2300312307 are available)

© 2004 United Press International, Inc. All Rights Reserved. Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.
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