In 2004, when the world was just discovering Gmail and the United States of America (US) was fighting a war in Iraq, NASA launched the now longest-running Mars Rover called Opportunity. The rover landed in a region of the Red Planet called Meridiani Planum on January 24, 2004, sending its first signal back to Earth. On March 20, 2004, Opportunity used a wheel to dig a trench revealing subsurface material. Photo: NASASelfie moment: Opportunity caught its own silhouette in this late-afternoon image taken by the rover's rear hazard avoidance camera. The rover, designed to travel only 1,100 yards and operate on the Red Planet for 90 Martian days, has travelled over 45 kilometres and logged its 5,000th Martian day in February, 2018. Photo: NASAOf its 15-year-long journey, Opportunity has spent 13 years exploring a small region of Meridiani Planum. A photo of this region as seen by NASA's Mars Reconnaissance Orbiter (MRO). Photo: NASAIt found an iron meteorite on Mars, the first meteorite of any type ever identified on another planet. One of Opportunity's greatest scientific finding was confirming the presence of standing water on Mars. It affirmed the presence of hematite, gypsum rocks on Mars that are usually found in water. Photo: NASAA false-color image of the dune field in Endurance Crater, taken by Opportunity. The rover has shown the world that it’s possible to operate one for more than a decade on another planet. Photo: NASAThe rover was last heard from on June 10, 2018, following which, a heavy planet-wide dust storm blanketed its location on Mars. One of the last images of Opportunity produced by the Mars Reconnaissance Orbiter (MRO), shows the rover on the slopes of the planet's Perseverance Valley. NASA still hasn't heard from the Opportunity rover, and it’s probably feared dead. However, in a last ditch attempt, NASA's Jet Propulsion Laboratory is sending a new set of commands to the rover, hoping to revive it. Photo: NASA