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Tuesday, January 14, 2003
The launch dates for the two Mars Exploration Rovers are getting closer
and so is the need to pick a place for them to land.
Adventurous travelers might spin a globe and pick a vacation based on
whichever spot their finger finds. But scientists and engineers working on
NASA's newest rover mission cannot be as casual about landing site choices for
the twin rovers that will launch in May and June of this year.
Last week, team members and others from the scientific community met for a
final chance to discuss and fine-tune the pros and cons of each of the four
landing site contenders.
Images and data from two other NASA spacecraft currently orbiting the red
planet -- Mars Global Surveyor and Mars Odyssey -- have provided invaluable
information on possible landing sites.
"This is a unique period where we have orbital missions that can help us
make the selection," said Dr. Matt Golombek, JPL landing site scientist.
"We want to go to sites with terrains that will challenge our minds but not
the safety of the rovers."
Since the rovers do not have the luxury of landing on a well-paved runway,
JPL geologists and engineers must carefully choose an area without large
rocks that could damage the rovers' airbag landing system. Also, an area
that is too densely populated with rocks of any size could prevent the rover
from moving freely. Winds in the lower atmosphere are also an important
consideration, as are the slopes the airbag-clad lander impact against.
Adequate exposure to the sun is vital for the solar-powered
rovers. Geologists have chosen sites near the equator where
there is sufficient sunlight. The sites are also relatively free
of accumulations of iron-oxide dust particles that can coat
solar panels and interfere with the rovers' mobility.
Like the final four in any competition, each of the four Mars
candidates is a potential winner.
"Three of the sites, Terra Meridiani, known as the Hematite site, Gusev,
and Isidis show evidence for surface processes involving water. These sites
appear capable of addressing the science objectives of the rover missions:
to determine if water was present on Mars and whether there are conditions
favorable to the preservation of evidence for ancient life," said Golombek.
The fourth site, Elysium, appears to contain ancient terrain, which may
hold clues to Mars' early climate when conditions may have been wetter.
Over the next several months, geologists and engineers will continue to
analyze the viability of each site. The final decision will be made by NASA
in April, shortly before the rovers begin their journey to Mars.
