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Mystery Rock 'Appears' in Front of Mars Rover

After a decade of exploring the Martian surface, the scientists overseeing veteran rover Opportunity thought they'd seen it all. That was until a rock mysteriously "appeared" a few feet in front of the six wheeled rover a few days ago.

News of the errant rock was announced by NASA Mars Exploration Rover lead scientist Steve Squyres of Cornell University at a special NASA Jet Propulsion Laboratory "10 years of roving Mars" event at the California Institute of Technology (Caltech), Pasadena, Calif., on Thursday night. The science star-studded public event was held in celebration of the decade since twin rovers Spirit and Opportunity landed on the Red Planet in January 2004.

PHOTOS: Alien Robots That Left Their Mark on Mars

While chronicling the scientific discoveries made by both rovers over the years, Squyres discussed the recent finding of suspected gypsum near the rim of Endeavour Crater - a region of Meridiani Planum that Opportunity has been studying since 2011 - and the discovery of clays that likely formed in a pH-neutral wet environment in Mars past. While these discoveries have been nothing short of groundbreaking, Squyres shared the Mars rover's team's excitement for that one strange rock, exclaiming: "Mars keeps throwing new stuff at us!"

Steve Squyres discusses the gypsum vein discovered by Mars rover Opportunity, another piece of the Martian water puzzle. | Ian O'Neill/Discovery News

In a comparison of recent photographs captured by the rover's panoramic camera, or Pancam, on sol 3528 of the mission, only bare bedrock can be seen. But on sol 3540, a fist-sized rock had appeared (raw Pancam images can be found in the mission archive). MER scientists promptly nicknamed the object "Pinnacle Island."

"It's about the size of a jelly doughnut," Squyres told Discovery News. "It was a total surprise, we were like 'wait a second, that wasn't there before, it can't be right. Oh my god! It wasn't there before!' We were absolutely startled."

But the rover didn't roll over that area, so where did Pinnacle Island come from?

Photos: Weirdest Mars Craters Spotted by HiRISE

Only two options have so far been identified as the rock's source: 1) The rover either "flipped" the object as it maneuvered or, 2) it landed there, right in front of the rover, after a nearby meteorite impact event. The impact ejecta theory, however, is the least likely of the two.

"So my best guess for this rock ... is that it's something that was nearby," said Squyres. "I must stress that I'm guessing now, but I think it happened when the rover did a turn in place a meter or two from where this rock now lies."

Opportunity's front right steering actuator has stopped working, so Squyres identified that as the possible culprit behind the whole mystery.

Each wheel on the rover has its own actuator. Should an actuator jam or otherwise fail, the robot's mobility can suffer. In the case of this wheel, it can no longer turn left or right. "So if you do a turn in place on bedrock," continued Squyres, "as you turn that wheel across the rock, it's gonna kinda 'chatter.'" This jittery motion across the bedrock may have propelled the rock out of place, "tiddlywinking" the object from its location and flipping it a few feet away from the rover.

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Never missing a scientific opportunity, Opportunity scientists hope to study the bright rock. "It obligingly turned upside down, so we're seeing a side that hasn't seen the Martian atmosphere in billions of years and there it is for us to investigate. It's just a stroke of luck," he said.

"You think of Mars as being a very static place and I don't think there's a smoking hole nearby so it's not a bit of crater ejecta, I think it's something that we did ... we flung it."

Although this is the leading theory behind the case of the random rock, Squyres pointed out that the investigation is still under way and it will be a few days before his team can definitively say where Pinnacle Island came from.

Opportunity has outlived its 3-month primary mission by ten years, notching up nearly 23 miles on the odometer so far. Sister rover Spirit succumbed to the Martian elements in 2009 when it became stuck in a sand trap in Gusev Crater. Spirit's mission was declared lost when it stopped transmitting in March 2010, likely drained of energy. Although Spirit had the rougher time on Mars and was the first to die, it was also a huge success, aiding our understanding of of Mars' geological history and outliving its warranty by 5 years. But now it's just Opportunity and Mars' new arrival Curiosity that soldier on to reveal more than we ever dreamed about our neighboring Red Planet.

As the NASA Jet Propulsion Laboratory rover drivers, scientists and engineers recounted stories of their beloved robots on Thursday, it became very clear that they aren't just machines of discovery, they are family.

A comparison of two raw Pancam photographs from sols 3528 and 3540 of Opportunity's mission (a sol is a Martian day). Notice the "jelly doughnut"-sized rock in the center of the photograph to the right. Minor adjustments for brightness and contrast.

Alien Robots That Left Their Mark on Mars

Aug. 24, 2012 --

Since the dramatic powered landing of NASA's Mars Science Laboratory (MSL) on Aug. 5/6, the one-ton rover has achieved a number of "firsts." It was the first planetary mission to use the exciting Sky Crane maneuver; the first to shoot lasers (for science); it's even the first nuclear-powered rover to put tread marks into Martian dirt. But it certainly isn't the first rover on the Red Planet -- two generations of Mars rover came before it. And the numerous stationary landers have also left their mark. To any hypothetical Martians on the Red Planet, it may look like an alien invasion is underway -- but these aliens come from the Blue Planet and they seem to insist on sending wave after wave of increasingly sophisticated robotic probes that dig, burn, scour and damage their pristine landscape! So, as we watch the incredible Curiosity rover dominate Gale Crater, it's time to take a step back and contemplate how these surface missions have changed the Martian landscape.

The First Rove As we ooh and aah over Curiosity's plus-sized wheel marks, it's time to turn the clock back to 1997 when a 2-foot long wheeled robot made its first, tentative sojourn onto Mars. NASA's Mars Pathfinder mission was the first successful rover mission to the Red Planet (the first attempts were the Soviet Mars 2 and Mars 3 surface missions in 1971 -- both failed) that saw the Sojourner rover explore its landing site for over 80 days after landing on July 4. Its primary mission was only seven days. The little rover left behind plenty of tire tracks that likely persisted for some time after the mission concluded -- they probably quickly became filled with Mars dust and eroded by winds.

Orbital Tracks The immensely successful Mars Exploration Rover (MER) Opportunity is in its ninth year of operations since landing on Mars on Jan. 25, 2004. As the rover continues to explore the Red Planet, notching up over 20 miles on the odometer (so far!), it has also left an impressive history of tire tracks. Amazingly, these tracks can be seen from orbit and NASA's Mars Reconnaissance Orbiter (MRO) has been able to keep a close eye over its roving cousin from space using its High-Resolution Imaging Science Experiment (HiRISE) camera. In this orbital snapshot, Opportunity can be seen at the edge of Victoria Crater (in 2006), plus wheel tracks. Like Sojourner, these tracks are not permanent, Mars' weather will erode them over time. So it's fortunate that Opportunity is still roving, creating new tracks.

Trench Digging MER Spirit, Opportunity's ill-fated sister rover, also surpassed her "warranty" by five years after landing on Mars on Jan. 4, 2004. Sadly, after becoming immobilized in a sand trap inside Gusev Crater in 2009, rescue attempts failed and the rover was confirmed lost after it stopped transmitting in March 2010. Spirit didn't travel as far as Opportunity -- logging nearly 5 miles -- and had a harder time on the surface of Mars. Early in the mission on March 13, 2006, one of the rover's wheels ceased working, forcing rover drivers to drive Spirit backwards, dragging the dead wheel behind it. Serendipitously, the frozen wheel became a handy trench-digger, creating a deep groove in the loose top soil as it roved. Material that would have otherwise been inaccessible could be glimpsed. Spirit's roving tracks will therefore likely remain visible on Mars for some time to come due to a sticky wheel.

Branding Rocks But it's not just tire tracks Spirit and Opportunity left on Mars, they have created a rather more permanent calling card. Using the rock abrasion tool mounted to both rovers' robotic arms, the wheeled robots have scoured the surface layers off a number of rocks for scientific study. On each rock, a 45 millimeter diameter circular "branding" has been left behind.

Laser Tattooing Rocks Although tagging rocks with circles is certainly cool (and of high scientific merit), the new rover on the Mars block has been outfitted with an instrument to laser-blast rocks with. Curiosity's ChemCam instrument mounted atop its mast can shoot rocks at a distance with a powerful laser beam, burning the surface layers. The resulting flash of light contains information about the rock's constituents, which ChemCam analyzes. Like Spirit and Opportunity, Curiosity can leave its own calling card -- a tiny, permanent laser'd tattoo.

Bouncy Bouncy Landing on Mars is serious business, and some very inventive methods have been used. The 1997 Mars Pathfinder mission, for example, touched-down with a bounce -- airbags were deployed, ensuring a cushioned impact with the ground after descent through the atmosphere. Airbags were also deployed during the landings of Spirit and Opportunity in January 2004. In this photograph, Opportunity retraced its bounce-marks to see impressions of the airbags preserved in the Martian regolith. The bags' seams can be seen. As the airbag bounce only imprinted the uppermost surface, it's likely these impressions were rapidly blown away and/or covered with dust.

Rocket Excavation Of course, Curiosity has to go one-better than its predecessors. During the powered landing of the rover, the Sky Crane's rocket-powered assembly delivered a huge amount of thrust to make sure Curiosity had a soft landing (air-bags aren't a viable landing method when delivering a rover the size of a car). Although debris was blown atop the rover, potentially damaging a wind sensor, the maneuver was a resounding success. But evidence of the landing has been spied around the rover. Areas of excavated material, creating shallow craters, surrounded the rover after landing. This ended up being a fortuitous event -- loose surface layers of dust and gravel were blown away, exposing the bedrock of Gale Crater. The bedrock has been the focus of study and the craters will likely be some long-term scarring of the Martian surface.

Crash and Burn Although the Sky Crane landed Curiosity safely to the surface, the rocket-powered platform suffered a messy demise. After its job was done, it throttled-up and flew far away from the rover, ditching into the Mars landscape. This HiRISE image shows the carnage that the Sky Crane's mass left behind after impact -- a site to remember the Sky Crane's good work.

Man-Made Meteorites Shortly after Curiosity entered the Martian atmosphere, as it began its descent, the rover's aeroshell (a capsule composed of a heatshield and backshell) jettisoned six 55-pound (25-kilogram) tungsten slugs to improve its stability as it used the Martian atmosphere to steer to its target. These ballast slugs slammed into the Martian surface -- basically man-made meteorites -- and could be spotted from orbit.

Phoenix With all the excitement surrounding rovers, it's about time to remember the not-so-mobile Mars explorers. On May 25, 2008, NASA's Phoenix Mars Lander touched down in Mars' arctic region to carry out experiments in a region we know little about. Using its arm-mounted scoop, the lander was able to retrieve samples from the freezing ground, dropping the material into its chemical laboratory for analysis. Phoenix made the landmark discovery of perchlorate in the soil and found water ice (that slowly sublimated) in the uppermost layers of the permafrost. Although Phoenix was never going to last long -- the arctic winter most likely cocooned the robot in ice. By Nov. 2, 2008, the mission was declared lost. Surrounding the landing site, however, small trench marks will likely remain -- remnants of Phoenix's science.

The Trendsetter NASA's first landers also left their mark on Mars. The Viking landers were hugely successful, returning the first images from the Martian surface and carrying out a suite of experiments to directly search for microbial life. Viking 1 lasted from July 1976 to November 1982; Viking 2 lasted from September 1976 to April 1980. To this day, the Viking experimental results are debated, but the deep trenches that were dug likely remain behind. MORE: Mars Curiosity 'Litter Bug' Spied from Orbit: Photos