[meteorite-list] Opportunity: Longest-Running Mars Rover

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 30 Oct 2012 15:39:28 -0700 (PDT)
Message-ID: <201210302239.q9UMdSKb013983_at_zagami.jpl.nasa.gov>

http://www.space.com/18289-opportunity-rover.html?

Opportunity: Longest-Running Mars Rover
Elizabeth Howell
space.com
October 30, 2012

Opportunity passed its warranty date long ago, but the rover is still healthy
and changing our perceptions of Mars after years of work on the Red Planet.

Initially intended to last 90 Martian days or "sols," Opportunity has now
driven more than 20 miles and explored two large craters: Victoria and
Endeavour. Along the way, the rover has found multiple signs of water - while
surviving a sand trap and bad dust storm.

 Opportunity and its twin rover, Spirit, received their names from 9-year-old
Sofi Collis. She was the winner of a naming contest NASA held (with assistance
from the Planetary Society and sponsorship from Lego) to find monikers for the
Mars Exploration Rovers. Siberian-born Collis was adopted at age two and came
to live with her new family in Scottsdale, Arizona.

"I used to live in an orphanage," Collis wrote in her winning essay. "It was
dark and cold and lonely. At night, I looked up at the sparkly sky and felt
better. I dreamed I could fly there. In America, I can make all my dreams come
true. Thank you for the 'Spirit' and the 'Opportunity.'"

The Mars Exploration Rovers launched in 2003 on a 283-million-mile (455.4 million
km) journey to hunt for water on Mars. The $800-million cost for the two of them
covered a suite of science instruments. Site survey tools included a panoramic
camera, as well as a mini-thermal emission spectrometer that was supposed to
search for signs of heat. Each rover also had a small arm with tools such as
spectrometers and a microscopic imager.

Cruise to Mars

Opportunity left Earth July 7, 2003, aboard a Delta II rocket en route to a landing
site at the Martian equator called Meridiani Planum. NASA was intrigued by a layer
of hematite that the orbiting Mars Global Surveyor spotted from above. As hematite
(an iron oxide) often forms in a spot that had liquid water, NASA was
curious about how the water got there in the first place and where the
water went.
 
The 384-pound rover made its final approach to Mars on January 25, 2004. It plowed
through the Martian atmosphere, popped out a parachute and then vaulted to the
surface in a cocoon of airbags.

Opportunity rolled to a stop inside a shallow crater just 66 feet (20 meters) across,
delighting scientists as the first pictures beamed back from the Red Planet.
"We have scored a 300-million mile interplanetary hole-in-one," quipped
Cornell University's Steve Squyres, principal investigator for the rover's
science instruments, in a press release in the days after the landing.

Early sols of science

Opportunity and Spirit (which had landed successfully three weeks earlier, on Jan. 3,
2004) had a primary goal to "follow the water" during their time on Mars. They would
hunt for any environments that showed evidence of water activity, particularly looking
for minerals that may have been left behind after water came through.

Both rovers met that goal quickly. In early March, just six weeks after landing,
Opportunity identified a rock crop that showed evidence of a liquid past. The rocks
at "Guadalupe" had sulfates as well as crystals inside of niches, which
are both signs of water. Spirit found water evidence of its own that same
week.

Two weeks later, Opportunity found hematite inside some small spheres
that NASA dubbed "blueberries" because of their size and shape. Using
a spectrometer, Opportunity found evidence of iron inside a group of berries
when comparing it to the bare, underlying rock.

The month wasn't yet over when Opportunity found more evidence of water, this time
from images of a rock outcrop that probably formed from a deposit of saltwater in
the ancient past. Chlorine and bromine found in the rocks helped solidify
the theory.

All in all, it was a positive start to Opportunity's mission
- and it hadn't even left the crater where it had landed yet. Before Opportunity's
90-day prime mission was over, the golf-cart size rover clambered out
of Eagle Crater and ventured to its next science target about half a mile
away: Endurance Crater. It spotted more water signs there in October.


Stuck in the sand

One of Opportunity's most dangerous moments came in 2005,
when the rover was mired in the sand for five weeks. NASA had put the
rover into a "blind drive" on April 26, 2005, meaning the rover was not
checking for obstacles as it went. Opportunity then plowed into a 12-inch-high
(30 cm) sand dune, where the six-wheeled rover initially had trouble getting
out.

To save the stranded rover, NASA ran tests on a model of the rover
in a simulated Martian "sandbox" at the Jet Propulsion Laboratory. Based
on what they learned in the sandbox, the rover drivers then sent a series
of commands to Opportunity. It took the rover about 629 feet (191 meters)
of wheel rotations before it was able to move forward three feet, but
it cut itself free in early June 2005.

NASA chose to move the rover forward in more careful increments, which was
especially important because Opportunity lost the full use of its right-front
wheel (because of a seized steering motor) just days before it got stuck in the
sand. The rover could still move around just fine with its other three steerable
wheels, NASA said.

Opportunity's experience in the sand came in handy in October 2005, when NASA
detected unusual traction problems on Sol 603. Just 16 feet into a planned 148-foot
drive, a slip check system on board automatically stopped the rover when
it went past a programmed limit. Two Martian days later, Opportunity backed
itself out of the problem and kept on going.

A marathon on Mars

In late September 2006, Opportunity wheeled up to Victoria Crater after 21 months
on the road. It circled the rim for a few months snapping pictures and
getting a close look at some layered rocks surrounding the crater. NASA
then made a gutsy decision in June 2007 to take Opportunity inside the
crater. It was a risk to the rover as it might not have been able to climb
up again, but NASA said the science was worth it.

"The scientific allure is the chance to examine and investigate the compositions and
textures of exposed materials in the crater's depths for clues about ancient, wet
environments," NASA stated in a press release. "As the rover travels farther
down the slope, it will be able to examine increasingly older rocks in
the exposed walls of the crater."

The trek down was interrupted by a severe dust storm in July 2007. Opportunity's
power-generating capabilities dropped by 80 percent in only one week as its solar
panels became covered in dust. Late in the month, Opportunity's power dipped to
critical levels. NASA worried the rover would stop working, but Opportunity pulled
through.

It wasn't until late August that the skies cleared enough for Opportunity
to resume work and head into the crater. Opportunity spent about a year
wandering through Victoria Crater, getting an up-close look at the layers
on the bottom and figuring that these were likely shaped by water.

Opportunity climbed out successfully in August 2008 and began a gradual journey to
Endeavour, an incredible 13 miles (21 km) away. It took about three years
to get there, as the rover was stopping to look at interesting science
targets on the way. But Opportunity successfully arrived in August 2011.

Opportunity is still doing science there today, beaming back findings such as a
mineral vein deposited by water. The little rover has completed nearly a marathon's
worth of mileage on Mars.
Received on Tue 30 Oct 2012 06:39:28 PM PDT