Posted on 10/07/2004 6:50:28 PM PDT by NormsRevenge
LOS ANGELES (AP) - NASA's Mars rovers don't seem to be wearing out so mission planners have begun to think more boldly, including a plan to let one climb up a steep "escape hatch" from a crater it has been exploring and set out on a trek across a plain.
"The rovers have lasted longer than expected, but as long as we have them we're going to keep them busy," project manager Jim Erickson said Thursday in a conference call with reporters.
Already on the second extension of their mission, the rovers Spirit and Opportunity have lasted so long that mission scientists have left NASA's Jet Propulsion Laboratory and returned to their own institutions, working via telephone and video conferences and remote networking.
"We realized that if we were going to make rover operations sustainable over the long term we were going to have to let people go back and live at their homes again," said Steve Squyres, rover mission principal investigator, of Cornell University.
Since landing on opposites sides of Mars in January, both of the six-wheel robot geologists have found evidence of past water activity, including new discoveries by Opportunity of rocks with polygon- shaped fractures that could indicate two eras of water activity in a crater named Endurance.
Despite being well over the planned mission life, the rovers are still capable. Controllers may even have Opportunity leave Endurance Crater soon via a 25- to 30-degree slope dubbed "escape hatch."
"It is right on the hairy edge of what we think the vehicle is capable of," Squyres said.
Opportunity could always retreat and leave the crater via the route it entered, but planners don't want to backtrack en route to new targets.
After leaving the crater they want Opportunity to examine for engineering purposes the heat shield that fell away during landing and impacted the surface at more than 100 mph.
"We're going to take a careful look at that and then at that point we're going to set sail," Squyres said.
The next target would require a 1 1/2-mile trip across the smooth Meridiani plains to a place called "etched terrain," where scientists believe they will find rocks exposed by the gentle erosion of wind, unlike the rocks they've found so far that were exposed by violent impact events.
Spirit, meanwhile, has a balky right front wheel after a nearly two-mile roll across the vast Gusev Crater region to the Columbia Hills. Controllers have continued to drive it with five wheels while saving the problem wheel for situations when it is needed.
Last week Spirit failed to perform a planned drive and controllers discovered that a brake on the steering motors for its right front and left rear wheels did not release. But the problem vanished and the rover resumed driving.
"As the vehicles age we may very well see aches and pains begin to happen here and there. We'll have to learn to deal with the problems as we go," Erickson said.
The rovers together have sent to Earth some 50,000 images, including a new 360-degree panorama from Spirit, looking back from its position in the hills. The view includes parts of the rover, the drop-off to the plain, a distant ridge and the walls of Gusev Crater about 50 miles away.
"The achievement of getting across the plains, getting into these hills that we never dreamed that we could reach back in January," said Jim Bell of Cornell, lead scientist for the panoramic cameras.
Other new images included wispy sand dunes photographed by Opportunity at the bottom of Endurance Crater. Opportunity drove down toward the dunes but was halted because the terrain became too soft.
"We were sort of clawing our way back on to solid ground as effectively as we could" when by chance the rover ended up by a rock with "a remarkable pattern of fractures," Squyres said.
John Grotzinger, a science team member from the Massachusetts Institute of Technology, said the fractures on the rock, named Escher, "tend to be organized to form what looks like discrete polygons."
Such fractures in Earth rocks have occurred where water impregnates sediments or loosely consolidated rocks, then evaporates.
"The rock dries out and as it reduces its volume and contracts it pulls in all directions. And if that stress is applied in all directions, you will often get polygonal fractures," Grotzinger said.
Study of how the fracturing overprints the layering of the rock raises a "remote" possibility that the rocks were wet a second time and again dried out, he said.
One possibility is that during one of Mars' climate changes there was a phase when frost accumulated in the crater and melted, penetrating the porous rocks.
"The other possibility, and we consider this to be the remotest of all, is perhaps the Endurance Crater itself filled up with a shallow lake," he said. "It might have existed for only the briefest of times, but if it did get the rocks wet, then they would have potentially fractured in this way."
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On the Net:
JPL: http://www.jpl.nasa.gov
Mars Rovers Probing Water History at Two Sites
NASA's Spirit and Opportunity have been exploring Mars about three times as long as originally scheduled. The more they look, the more evidence of past liquid water on Mars these robots discover. The image above shows the rock dubbed "Escher," which helps support these new findings.
This image, taken by the panoramic camera on NASA's Mars Exploration Rover Spirit during the rover's trek through the "Columbia Hills" at "Gusev Crater," shows the horizontally layered rock dubbed "Tetl." Scientists hope to investigate this rock in more detail, aiming to determine whether the rock's layering is volcanic or sedimentary in origin. If for some reason this particular rock is not favorably positioned for grinding and examination by the toolbox of instruments on the rover's robotic arm, Spirit will be within short reach of another similar rock, dubbed "Coba." more
This stunning image mosaic of the "Columbia Hills" is the first 360-degree panorama taken since the Mars Exploration Rover Spirit arrived at the hills over a month ago. The rover has been busy studying the rocks here, which show evidence of past alteration by water. The dark patch of soil to the right is the spot where Spirit stopped for engineering work on its right front wheel. Spirit's tracks can be followed from there all the way back to "Bonneville Crater" and the original landing site, more than 3 kilometers (1.86 miles) away.
This approximate true-color image, nicknamed the "Cahokia panorama" after the Native American archaeological site near St. Louis, was acquired between sols 213 to 223 (Aug. 9 to 19, 2004). The panorama consists of 470 images acquired through six panoramic camera filters (750 to 480 nanometers). It took until the week of sol 237 (Sept. 2) to downlink all the data back to Earth. Several more weeks of image processing and geometric mapping by team members at Jet Propulsion Laboratory, Pasadena, Calif., and Cornell University, Ithaca, N.Y., to stitch all the images together into this spectacular mosaic.
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