Two months after sky-darkening dust from severe
storms nearly killed NASA's Mars exploration rovers, the
solar-powered robots are awake and ready to continue their mission.
Opportunity's planned descent into the giant Victoria Crater was
delayed, but now the rover is preparing to drive into the half-mile
diameter crater as early as Sept. 11.
Spirit, Opportunity's rover twin, also survived the global dust storm.
The rovers are 43 months into missions originally planned to last
three months. On Sept. 5, Spirit climbed onto its long-term
destination called Home Plate, a plateau of layered bedrock bearing
clues to an explosive mixture of lava and water.
"These rovers are tough. They faced dusty winds, power starvation and
other challenges -- and survived. Now they are back to doing
groundbreaking field work on Mars. These spacecraft are amazing, "
said Alan Stern, associate administrator of NASA's Science Mission
Directorate, Washington.
Victoria Crater contains an exposed layer of bright rocks that may
preserve evidence of interaction between the Martian atmosphere and
surface from millions of years ago, when the atmosphere might have
been different from today's. Victoria is the biggest crater
Opportunity has visited.
Martian dust storms in July blocked so much sunlight that researchers
grew concerned the rovers' daily energy supplies could plunge too low
for survival. Engineers at NASA's Jet Propulsion Laboratory,
Pasadena, Calif., put Opportunity onto a very low-energy regimen of
no movement, few observations and reduced communication with Earth.
Skies above both rovers remain dusty but have been clearing gradually
since early August.
Dust from the sky has been falling onto both rovers' solar panels,
impeding their ability to collect energy from the sun. However,
beneficial wind gusts removed some of the new buildup from
Opportunity almost as soon as it accumulated.
Opportunity drove to the lip of Victoria Crater in late August and
examined possible entry routes. This week, Opportunity has been
driving about 130 feet toward its planned entry point. The route will
provide better access to a top priority target inside the crater: a
bright band of rocks about 40 feet from the rim. "We chose a point
that gives us a straight path down, instead of driving cross-slope
from our current location, " said Paolo Bellutta, a JPL rover driver
plotting the route. "The rock surface on which Opportunity will be
driving will provide good traction and control of its path into the
crater."
For its first foray into the crater, Opportunity will drive just far
enough to get all six wheels in; it will then back out and assess
slippage on the inner slope. "Opportunity might be ready for that
first 'toe dip' into the crater as early as next week, " said JPL's
John Callas, rover project manager. "In addition to the drives to get
to the entry point, we still need to conduct checkouts of two of
Opportunity's instruments before sending the rover into the crater."
The rover team plans to assess if dust has impaired use of the
microscopic imager. If that tool is working, the team will use it to
observe whether a scanning mirror for the miniature thermal emission
spectrometer (Mini-TES) can function accurately. This mirror is high
on the rover's camera mast. It reflects infrared light from the
landscape to the spectrometer at the base of the mast, and it also
can be positioned to close the hole in the mast as protection from
dust. The last time the spectrometer was used, some aspects of the
data suggested the instrument may have been viewing the inside of the
mast instead of the Martian landscape.
"If the dust cover or mirror is no longer moving properly, we may have
lost the ability to use that instrument on Opportunity, " said Steve
Squyres of Cornell University, Ithaca, N.Y., principal investigator
for the rovers' science instruments. "It would be the first permanent
loss of an instrument on either rover. But we'll see."
The instrument already has provided extensive valuable information
about rocks and soils in the Meridiani region where Opportunity
works. "Mini-TES has told us a lot about the rocks and soils at
Meridiani, but we've learned that the differences among Meridiani
rocks are often too subtle for it to distinguish, " Squyres said. "The
same instrument on Spirit, at Gusev Crater, has a much more crucial
role for us at this point in the mission because there is such
diversity at Gusev." Researchers will rely heavily on a different
type of instrument, Opportunity's alpha particle X-ray spectrometer,
for analysis of rocks at the bright-band target layer in the crater.
For images and information about the rovers, visit:
http://www.nasa.gov/rovers
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