Durable NASA Rover Beginning Ninth Year of Mars Work
On the eighth anniversary of starting to explore Mars, NASA's rover Opportunity remains busy with new investigations.
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/roversandhttp://marsrovers.jpl.nasa.gov.  You can follow the project on Twitter athttp://twitter.com/MarsRoversand on Facebook athttp://www.facebook.com/marsrovers.