[meteorite-list] NASA's Mars Rover Spirit Faces Circuitous Route

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 5 Mar 2009 12:31:03 -0800 (PST)
Message-ID: <200903052031.MAA04929_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2009-041

NASA's Mars Rover Spirit Faces Circuitous Route
Jet Propulsion Laboratory
March 05, 2009

PASADENA, Calif. -- Loose soil piled against the northern edge of a low
plateau called "Home Plate" has blocked NASA's Mars Exploration Rover
Spirit from taking the shortest route toward its southward destinations
for the upcoming Martian summer and following winter.

The rover has begun a trek skirting at least partway around the plateau
instead of directly over it.

However, Spirit has also gotten a jump start on its summer science
plans, examining a silica-rich outcrop that adds information about a
long-gone environment that had hot water or steam. And even a circuitous
route to the destinations chosen for Spirit would be much shorter than
the overland expedition Spirit's twin, Opportunity, is making on the
opposite side of Mars.

Both rovers landed on Mars in 2004 for what were originally planned as
three-month missions there.

Spirit spent 2008 on the northern edge of Home Plate, a flat-topped
deposit about the size of a baseball field, composed of hardened ash and
rising about 1.5 meters (5 feet) above the ground around it. There, the
north-facing tilt positioned Spirit's solar arrays to catch enough
sunshine for the rover to survive the six-month-long Martian winter.

The scientists and engineers who operate the rovers chose as 2009
destinations a steep mound called "Von Braun" and an irregular,
45-meter-wide (150-foot-wide) bowl called "Goddard." These side-by-side
features offer a promising area to examine while energy is adequate
during the Martian summer and also to provide the next north-facing
winter haven beginning in late 2009. Von Braun and Goddard intrigue
scientists as sites where Spirit may find more evidence about an
explosive mix of water and volcanism in the area's distant past. They
are side-by-side, about 200 meters, or yards, south of where Spirit is now.

It's mid-spring now in the southern hemisphere of Mars. The sun has
climbed higher in the sky over Spirit in recent weeks.

The rover team tried to drive Spirit onto Home Plate, heading south
toward Von Braun and Goddard. They tried this first from partway up the
slope where the rover had spent the winter. Only five of the six wheels
on Spirit have been able to rotate since the right-front wheel stopped
working in 2006. With five-wheel drive, Spirit couldn't climb the slope.
In January and February, Spirit descended from Home Plate and drove
eastward about 15 meters (about 50 feet) toward a less steep on-ramp.
Spinning wheels in loose soil led the rover team to choose another of
its options.

"Spirit could not make progress in the last two attempts to get up onto
Home Plate," said John Callas of NASA's Jet Propulsion Laboratory,
Pasadena, Calif., project manager for both rovers. "Alternatively, we
are driving Spirit around Home Plate to the east. Spirit will have to go
around a couple of small ridges that extend to the northeast, and then
see whether a route east of Home Plate looks traversable. If that route
proves not to be traversable, a route around the west side of Home Plate
is still an option."

During the drive eastward just north of Home Plate in January, Spirit
stopped to use tools on its robotic arm to examine a nodular, heavily
eroded outcrop dubbed "Stapledon," which had caught the eye of
rover-team scientist Steve Ruff when he looked at images and infrared
spectra Spirit took from its winter position.

"It looked like the material east of Home Plate that we found to be rich
in silica," said Ruff, of Arizona State University, Tempe. "The silica
story around Home Plate is the most important finding of the Spirit
mission so far with regard to habitability. Silica this concentrated
forms around hot springs or steam vents, and both of those are favorable
environments for life on Earth."

Sure enough, Spirit's alpha particle X-ray spectrometer found Stapledon
to be rich in silica, too.

"Now we have found silica on a second side of Home Plate, expanding the
size of the environment we know was affected by hot springs or steam
vents," Ruff said. "The bigger this system, the more water was involved,
the more habitable this system may have been."

The contact measurement with the X-ray spectrometer also gave the team
confidence in its ability to identify silica-rich outcrops from a
distance with the rover's thermal emission spectrometer, despite some
dust that has accumulated on a periscope mirror of that instrument.
Researchers plan to use Spirit's thermal emission spectrometer and
panoramic camera to check for more silica-rich outcrops on the route to
Von Braun and Goddard. However, the team has set a priority to make good
progress toward those destinations. Winds cleaned some dust off Spirit's
solar panels on Feb. 6 and Feb. 14, resulting in a combined increase of
about 20 percent in the amount of power available to the rover.

Opportunity, meanwhile, shows signs of increased friction in its
right-front wheel. The team is driving the rover backwards for a few
sols, a technique that has helped in similar situations in the past,
apparently by redistributing lubricant in the wheel. Opportunity's major
destination is Endeavour Crater, about 22 kilometers (14 miles) in
diameter and still about 12 kilometers (7 miles) away to the southeast.
Opportunity has been driving south instead of directly toward Endurance,
to swing around an area where loose soil appears deep enough to
potentially entrap the rover.

JPL, a division of the California Institute of Technology, Pasadena,
manages the Mars Exploration Rovers for the NASA Science Mission
Directorate, Washington. More information about the rovers is at
http://www.nasa.gov/rovers .

Media contact: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Guy.Webster at jpl.nasa.gov
2009-041
Received on Thu 05 Mar 2009 03:31:03 PM PST