Durable NASA Rover Beginning Ninth Year of Mars Work

[ysabetwordsmith]

This piece of NASA news crossed my desk today.

Durable NASA Rover Beginning Ninth Year of Mars Work

Eight years after landing on Mars for what was planned as a three-month
mission, NASA's enduring Mars Exploration Rover Opportunity is working
on what essentially became a new mission five months ago.

Opportunity reached a multi-year driving destination, Endeavour Crater, in
August 2011. At Endeavour's rim, it has gained access to geological deposits
from an earlier period of Martian history than anything it examined during
its first seven years. It also has begun an investigation of the planet's
deep interior that takes advantage of staying in one place for the
Martian winter.

Opportunity landed in Eagle Crater on Mars on Jan. 25, 2004, Universal
Time
and EST (Jan. 24, PST), three weeks after its rover twin, Spirit, landed
halfway around the planet. In backyard-size Eagle Crater, Opportunity
found
evidence of an ancient wet environment. The mission met all its goals
within
the originally planned span of three months. During most of the next
four
years, it explored successively larger and deeper craters, adding
evidence
about wet and dry periods from the same era as the Eagle Crater
deposits.

In mid-2008, researchers drove Opportunity out of Victoria Crater, half
a
mile (800 meters) in diameter, and set course for Endeavour Crater, 14
miles
(22 kilometers) in diameter.

"Endeavour is a window further into Mars' past," said Mars Exploration
Rover
Program Manager John Callas, of NASA's Jet Propulsion Laboratory,
Pasadena,
Calif.

The trek took three years. In a push to finish it, Opportunity drove
farther
during its eighth year on Mars -- 4.8 miles (7.7 kilometers) -- than in
any
prior year, bringing its total driving distance to 21.4 miles (34.4
kilometers).

The "Cape York" segment of Endeavour's rim, where Opportunity has been
working since August 2011, has already validated the choice of Endeavour
as
a long-term goal. "It's like starting a new mission, and we hit pay dirt
right out of the gate," Callas said.

The first outcrop that Opportunity examined on Cape York differs from
any
the rover had seen previously. Its high zinc content suggests effects of
water. Weeks later, at the edge of Cape York, a bright mineral vein
identified as hydrated calcium sulfate provided what the mission's
principal
investigator, Steve Squyres of Cornell University, Ithaca, N.Y., calls
"the
clearest evidence for liquid water on Mars that we have found in our
eight
years on the planet."

Mars years last nearly twice as long as Earth years. Entering its ninth
Earth year on Mars, Opportunity is also heading into its fifth Martian
winter. Its solar panels have accumulated so much dust since Martian
winds
last cleaned them -- more than in previous winters -- the rover needs to
stay on a sun-facing slope to have enough energy to keep active through
the
winter.

The rover team has not had to use this strategy with Opportunity in past
winters, though it did so with Spirit, farther from the equator, for the
three Martian winters that Spirit survived. By the beginning of the
rovers'
fourth Martian winter, drive motors in two of Spirit's six wheels had
ceased
working, long past their design lifespan. The impaired mobility kept the
rover from maneuvering to an energy-favorable slope. Spirit stopped
communicating in March 2010.

All six of Opportunity's wheels are still useful for driving, but the
rover
will stay on an outcrop called "Greeley Haven" until mid-2012 to take
advantage of the outcrop's favorable slope and targets of scientific
interest during the Martian winter. After the winter, or earlier if wind
cleans dust off the solar panels, researchers plan to drive Opportunity
in
search of clay minerals that a Mars orbiter's observations indicate lie
on
Endeavour's rim.

"The top priority at Greeley Haven is the radio-science campaign to
provide
information about Mars' interior," said JPL's Diana Blaney, deputy
project
scientist for the mission. This study uses weeks of tracking radio
signals
from the stationary rover to measure wobble in the planet's rotation.
The
amount of wobble is an indicator of whether the core of the planet is
molten, similar to the way spinning an egg can be used to determine
whether
it is raw or hard-boiled.

Other research at Greeley Haven includes long-term data gathering to
investigate mineral ingredients of the outcrop with spectrometers on
Opportunity's arm, and repeated observations to monitor wind-caused
changes
at various scales.

The Moessbauer spectrometer, which identifies iron-containing minerals,
uses
radiation from cobalt-57 in the instrument to elicit a response from
molecules in the rock. The half-life of cobalt-57 is only about nine
months,
so this source has diminished greatly. A measurement that could have
been
made in less than an hour during the rover's first year now requires
weeks
of holding the spectrometer on the target.

Observations for the campaign to monitor wind-caused changes range in
scale
from dunes in the distance to individual grains seen with the rover's
microscopic imager. "Wind is the most active process on Mars today,"
Blaney
said. "It is harder to watch for changes when the rover is driving every
day. We are taking advantage of staying at one place for a while."

NASA's Jet Propulsion Laboratory, a division of the California Institute
of
Technology in Pasadena, manages the Mars Exploration Rover Project for
the
NASA Science Mission Directorate, Washington. More information about
Opportunity is online at: http://www.nasa.gov/rovers and
http://marsrovers.jpl.nasa.gov . You can follow the project on Twitter
at
http://twitter.com/MarsRovers and on Facebook at
http://www.facebook.com/marsrovers .

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov

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