mars_battlefield_010131 MOUNTAIN VIEW, Calif. -- Where to plunk down twin
Mars rovers on the Red Planet in early 2004 has sparked spirited debate among scientists and engineers. Battle lines are being drawn between these two camps, each weighing scientific payoff against technical worries in picking ultra-safe landing areas over more risky touchdown spots.
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Four of the possible landing sites for the 2004 rovers include Isidis, Gale Crater, Sinus Meridiani and Terra Meridiani. To see more sites under consideration, watch our video. |
Last week, here at the NASA Ames Research Center, top Mars researchers met January 24-25. They selected a handful of candidate exploration zones, including a section of
Valles Marineris, an enormous canyon system on Mars. Possible landing ellipses for the dual Mars Exploration Rovers -- simply dubbed MER-A and MER-B -- are being targeted for camera sweeps by the now-orbiting Mars Global Surveyor, which has been taking high-flying snapshots of potential touchdown locations for the missions since last December.
The actual landing spot for each rover will not be chosen until at least a year before they are launched in 2003.
Hazard-free sites
Hanging over the next Mars landing project is a cloud of residual doom and gloom from the late 1999 losses of NASAs
Mars Climate Orbiter and the Mars Polar Lander. On the other hand, the earlier July 1997 airbag landing of the highly successful Mars Pathfinder that unleashed the Sojourner mini-rover bolsters a can-do enthusiasm in the current teams.Of utmost concern is choosing huge "parking lot-like," hazard-free areas for the rovers. Smooth and flat areas are being sought over those locations that have large hills or are pocked with big craters. Spacecraft safety is paramount.
Moreover, spacecraft builders face a variety of engineering constraints. These include: avoiding large slopes so landing radar wont be spoofed into setting off retrorocket and airbag inflation systems too early or too late; making sure airbags that protect each rover at landing do not bounce into certain size rocks or roll down mega-slopes; and choosing a site that is not too dusty, otherwise the rovers lifetime could be shortened as dust gathers on the crafts energizing solar panels.
Next Page: Balancing Act
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Balancing act
For Mars researchers, engineering issues are headaches that wreak havoc with getting to prime Martian real estate.
One major issue is picking a site where each rover can cope with the "thermal inertia" of the surface. That means avoiding terrain where temperature changes swing too wildly. Surface materials can yield sweltering heat in the day and also cause temperatures to drop drastically at night.
"Mars is not flat. Its really time to change and start taking some risks. We made the same mistake 2,000 years ago thinking the Earth was flat. Lets go where Mars is showing us where to go."
Cold at night, in particular, can cripple a rover. Inner workings might be overwhelmed. Precious electrical power can be sucked up just to run heaters to keep a rover warm and well. Finding that temperature sweet-spot is a priority.
Balancing science objectives with engineering constraints is a continual process, said Matthew Golombek, Mars exploration program landing site scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, California.
"Where youre revising what you can do and the engineers are evaluating what they can do...you just keep going down that path for a long time," Golombek said.
| Where To Go? |
| Those attending the First Mars 2003 Landing Site Workshop reached a general consensus on the highest priority, medium priority, and sites eliminated from further consideration. |
Top candidate landing areas for MER-A and MER-B rovers are to be targeted for up-close imaging by the Mars Global Surveyor. |
These are: a trio of sites in Sinus Meridiani and Terra Meridiani that appear to have a deposit of hematite, likely the result of mineral deposition by water; Gale crater; an area south of Gusev crater; the Melas Chasma in Valles Marineris; a long outflow channel in Valles Marineris; the Elysium outflow; and the rim of Isidis, the site of an impressive valley network. |
"These guys are conservative. When an engineer says that they are going to do something, the blood comes out of the vein as they stake their entire careers on a decision. So they tend to be a little bit on the conservative side," Golombek said.
Flat Mars society
"Mars is not flat," said Nathalie Cabrol, a SETI Institute planetary geologist at NASA Ames. "Its really time to change and start taking some risks. We made the same mistake 2,000 years ago thinking the Earth was flat. Lets go where Mars is showing us where to go," she said.
Cabrol advocates exploring huge impact crater-lake basins on Mars. These locales, such as Schiaparelli, Gusev and Gale crater, act as time machines. Crater-lake exploration could become the Rosetta Stone of Mars, she said -- an all-in-one mission that learns about water and climate, geological history and life on the planet.
"Mars is beautiful. Its diverse. I would hate to learn again that Mars is flat with some boulders. We have been doing that for 25 years," Cabrol told SPACE.com.
Mars experts at the gathering pointed to numbers of scientifically rewarding sites.
For instance, the floor of Eos Chasma in Valles Marineris is particularly appealing. There a rover would be a scant 19 miles (30 kilometers) from the canyons southeast wall -- a robotic sightseers delight with a chance to scan the canyon walls sedimentary layering.
Then theres Apollinaris Patera, a unique region that offers a look at volcano-ground water interaction. Just as interesting is Ganges Chasma where numerous channels of water emptied. This area once may have been the site of the largest waterfall in the solar system.
Holding tight its mysteries
An outcome of the meeting is the selection of nine very high-priority sites, all exciting scientifically and each looking pretty safe, said Steve Squyres, planetary scientist at Cornell University in Ithaca, New York. He is also leading the team building the Athena science package to be hauled across Martian terrain by each wheeled rover.
"The hard part is going down from nine to two sites, but Im thrilled with this list," Squyres said. Images and other data cranked out by the Mars Global Surveyor of prospective sites will be key to the winnowing-down process.
"Some of these sites may drop off the list if the new images suggest that the current interpretation of whats there is not correct," Squyres said.
Bruce Jakosky, astrobiologist at the University of Colorado in Boulder, said care must be taken in studying potential Mars landing sites. What you see at one scale from orbit isnt necessarily what processes were at work at ground level, he said.
Even with more and more data being gleaned by Mars spacecraft, the Red Planet holds on tight to its mysteries, said Michael Carr, an astrogeologist at the U.S. Geological Survey in Menlo Park, California.
Carr said that instruments on the Mars Global Surveyor have shown Mars to be a totally different planet from what was seen during the Viking missions of the 1970s.
"Its just more difficult to understand because theres more information," Carr said. "Mars it seems is getting more and more complex," he said.
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