Mars Rovers Set to Break Red Planet Record

A historic milestone could be made on Mars this week.

On Thursday, NASA's beleaguered Spirit rover could become the longest-running mission on the surface of Mars, surpassing the Viking 1 lander's record of six years and 116 days of operation on the Martian surface ? if it's still alive, that is.

Spirit fell silent on Mars on March 31, when it skipped a planned communications session with Earth. It may be hibernating through the harsh Martian winter. But even if Spirit doesn't survive, its robotic twin Opportunity is poised to break the Mars mission record in early May.

Beating Viking's record, which NASA set in the 1980s, would be a major feat for a rover the size of a golf cart that was only supposed to last for three months and spent the past year stuck in Martian sand. The milestone would also be a welcome surprise to the team of scientists and engineers that have been commanding Spirit for these past six years.

"Being part of the team that will break the VL1 [Viking Lander 1] record will be exciting," said Ray Arvidson of the Washington University in St. Louis, who led the Viking Lander Imaging Team way back when and now serves as a member of the Spirit science team. "It means to me personally that I will have participated in two historical events."

Undying Spirit and Opportunity

Spirit and its robotic twin sister Opportunity landed on opposite sides of Mars in 2004 ? Spirit bounced onto the surface on Jan. 4, while Opportunity landed a few weeks later on Jan. 25 Eastern Time.

Both rovers were initially slated for just a 90-day mission to explore the geology and chemistry of their respective landing sites. But they blew past those deadlines and have continued their missions for far longer than mission engineers ever thought possible.

They passed their six-year marks in January of this year. That means right now both rovers are in the midst of their seventh Earth year on Mars.

"By lasting such a long time, the rovers have been able to accomplish far more science and exploration than we ever expected, and that's a wonderful thing. We're very proud of that," said Steve Squyres, lead scientist for the Mars Exploration Rover Project at Cornell University in Ithaca, NY.

In January of this year, after months of trying to rescue Spirit from a sand trap it rolled into in May 2009, NASA rechristened the rover as a stationary lander. Opportunity, meanwhile, is doing fine and headed to a giant crater called Endeavour on the Martian plains of Meridiani Planum.

Rovers vs. Vikings

Viking 1 was also a hardy spacecraft, lasting from the time it touched down on Mars on July 20, 1976 until contact was lost in November 1982, putting its time in operation on Mars at 6 years, 116 days. [Dead Mars spacecraft.]

The exact hour when Viking ceased operation is debatable, but NASA officials are marking April 29 as the day that Spirit will match Viking 1's record.

But NASA's Viking landers (there were two) used a radioisotope thermoelectric generator ? which converts heat from decaying nuclear material into electricity ? for power. Spirit and Opportunity use solar arrays that rely on available sunlight and periodic dust storms to keep them clean.

Of course, Spirit has been out of communication for the past four weeks after entering a low-power hibernation mode once winter sat in and temperatures dropped along with the sun dipping in the sky, leaving Spirit with little available power.

Because the rover is out of contact, mission managers may not know for several weeks whether or not Spirit survived and was still in operation on its record-setting day, and not before Opportunity matches the same record.

"A communication from Spirit on April 29 or later would be a confirmation that it has matched or exceeded VL1's longevity," said Guy Webster, a spokesman at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "That might not happen before Opportunity reaches the VL1 longevity mark, which will be on May 20."

Battle of the Mars-bots

If Spirit does survive the winter, it will hold the record over Opportunity, of course.

While Arvidson is doubtful that Spirit will break the record, pointing out how long the rover will have to stay in a low-power mode, Squyres is more optimistic.

"You could lose a lot of money betting against that rover," he told SPACE.com, alluding to the number of times the rover has improbably survived tough conditions on the Martian surface.

If the Spirit rover does wake up come spring, it will continue to investigate the area in which it became mired, checking out new soil targets in the fortuitously geologically-interesting spot.

How long Spirit, or Opportunity, might hold the longevity record is anyone's guess, and will at least hold out until the next Mars surface explorer, the Mars Science Laboratory (aka Curiosity) arrives at the red plant. Curiosity isn't slated to launch until 2011.

Even if Curiosity becomes the next rover to match the Viking 1 record, it will then have to catch up to whatever new benchmark the MER rovers set as they near their 7th anniversaries, and possibly even make it to later "birthdays."

• Images ? Mars: A Spacecraft Graveyard
• Most Amazing Mars Rover Discoveries
• Mars as Seen by Spirit and Opportunity, Part 2