It was only meant to last about three months, but NASA's Opportunity Mars rover has officially clocked up 5,000 Martian days exploring the Red Planet. That's a little over 5,151 Earth days in which the robotic geologist has traversed a record 28 mi (45 km) across the surface of Mars to unlock the secrets of the planet's history and geology – and it's not done yet. To commemorate this anniversary, New Atlas has put together a gallery of some of the mission's highlights from the past 14 years.

Exploring Mars isn't easy. It's a harsh environment far from home filled with nasty surprises that have put paid to more than one expensive mission. Worse, the Martian day is an aggravating 40 minutes longer than the one Earth. This means that mission control at the Jet Propulsion Laboratory (JPL) in Pasadena, California measures time in Martian "sols," or the duration of a solar day on Mars. This way, the mission planning and duty rosters remain in sync with Opportunity and other rovers on the planet.

Launched on July 7, 2003 atop a Delta II rocket from Cape Canaveral Air Force Station, Florida, the Boeing-built, 408-lb (185-kg) Opportunity is also known as Mars Exploration Rover-B (MER-A). It landed on the Meridiani Planum region of Mars on January 25, 2004, which was three weeks after its sister rover, Spirit (MER-A), touched down on the opposite side of the planet.

Opportunity was originally designed to operate for 90 sols (92 days), but the unmanned explorer turned out to be a classic example of NASA over-engineering that has continued to function productively for 55 times its designed service life and will continue to do so for who knows how long. Meanwhile, Spirit didn't fare as well. It, too lasted longer than designed, but became stuck in a sand dune in 2009 and remained there until communication was lost in 2010.

What's remarkable about Opportunity lasting so long is that, unlike the later Curiosity rover, it isn't nuclear powered. It relies on solar panels for its energy. So, whereas Curiosity isn't affected much by the weather, Opportunity suffers power shortages when dust and dirt accumulates on its panels and in the gloom of winter it has to give top priority to simply keeping its electronics warm. Due to this, mission control was surprised that the rover actually survived its first winter, much less reach sol 5,000 on February 15.

Thanks to its never-say-die attitude, Opportunity has had a long and productive career. So far it's studied the impact crater that it landed in by chance, then the surrounding flat plain, examined soil and rock samples, taken panoramic images, and has even photographed a passing comet.

In addition, it's discovered the presence of hematite and evidence of the past presence of water on Mars, provided a long baseline survey of the Martian surface, as well as a better understanding of the part water played in the formation of the region's minerals, calibrated observations by the Mars Reconnaissance Orbiter, sent back over 225,000 images, and helped to determine the likelihood of life existing or having existed on the planet. It even found the first meteorite ever discovered on Mars, which was thought at first to be a fragment of the landing platform's heat shield.

But it's also had some close calls. Opportunity was almost lost in 2005 when it became stuck in a sand dune and had to be extracted a few centimeters at a time. And, despite its longevity, in 2014 the rover's computer memory was failing and can now operate in a RAM-only configuration. However, that didn't stop it on July 28, 2014 from breaking the off-planet long distance record for a ground vehicle when its odometer passed 40 km (25 mi), which was followed by its completion of the distance of a marathon ( 42.195 km, 26.219 mi) on March 24, 2015.

"We've reached lots of milestones, and this is one more," says Opportunity Project Manager John Callas, of NASA's Jet Propulsion Laboratory in Pasadena, California, "but more important than the numbers are the exploration and the scientific discoveries."

Currently, Opportunity is about one-third of the way down Perseverance Valley, which is a shallow channel cutting into the rim of Endeavour Crater. Take a look through our gallery for a look at the journey that got it there.

Source: NASA

View gallery - 81 images