Photos: Mars Opportunity and Spirit rovers This image is a cropped version of the last 360-degree panorama taken by the Opportunity rover's panoramic camera from May 13 through June 10, 2018. The view is presented in false color to make some differences between materials easier to see. Hide Caption 1 of 21

Photos: Mars Opportunity and Spirit rovers Are those Martian blueberries? These tiny spherules pepper the sandy surface in this 3-centimeter (1.2-inch) square view of the Martian surface. Opportunity took this image while the target was shadowed by the rover's instrument arm. Hide Caption 2 of 21

Photos: Mars Opportunity and Spirit rovers From its perch high on a ridge, Opportunity recorded this image of a Martian dust devil twisting through the valley below. Just as on Earth, a dust devil is created by a rising, rotating column of hot air. When the column whirls fast enough, it picks up tiny grains of dust from the ground, making the vortex visible. Hide Caption 3 of 21

Photos: Mars Opportunity and Spirit rovers While traversing on and around the ancient volcanic feature called Home Plate, Spirit took many images of finely layered and more frothy looking volcanic rocks. Hide Caption 4 of 21

Photos: Mars Opportunity and Spirit rovers Opportunity photographed its tracks in the soft sand between the Endurance and Victoria craters on the Meridiani Plains. Hide Caption 5 of 21

Photos: Mars Opportunity and Spirit rovers More blueberries! Opportunity took this photo in 2004 of a rock called "Last Chance." The spherules embedded in the rock reminded the researchers of berries in muffins. The textures in the rock actually helped researchers determine that Mars had wet environmental conditions in the past. Hide Caption 6 of 21

Photos: Mars Opportunity and Spirit rovers Oppy's panoramic camera gathered this mosaic in 2014 of Wdowiak Ridge, as well as the rover's tracks to the right. This is about 70 degrees from north/northwest to east/northeast, showing the 500-feet ridge that rises 40 feet tall. Hide Caption 7 of 21

Photos: Mars Opportunity and Spirit rovers The rover took a selfie to show how much dust it had accumulated in 2011 before the windy season helped knock some of it off. Hide Caption 8 of 21

Photos: Mars Opportunity and Spirit rovers Sometimes, when Opportunity's solar power was limited, it would stop between treks to different features on Mars. This 2010 photo of its tracks on the surface show it "hopping from lily pad to lily pad." Hide Caption 9 of 21

Photos: Mars Opportunity and Spirit rovers The Mars Reconnaissance Orbiter took this photo of Victoria Crater, about a half-mile in diameter. It was Opportunity's home for 14 of the first 46 months it spent on Mars. Hide Caption 10 of 21

Photos: Mars Opportunity and Spirit rovers Opportunity's panoramic camera took this photo of outcrop rocks that it encountered on its journey in 2005. Cracks and other features are obvious. The two holes visible were drilled by the rover to expose the underlying material. Hide Caption 11 of 21

Photos: Mars Opportunity and Spirit rovers A shadow selfie. On July 26, 2004, the rover took this photo commemorating its 90 days on Mars -- the amount of time the mission was supposed to last. Instead, it continued for 15 years. Hide Caption 12 of 21

Photos: Mars Opportunity and Spirit rovers Opportunity made an impact. A panoramic image shows the heat shield impact site when it landed in 2004. Hide Caption 13 of 21

Photos: Mars Opportunity and Spirit rovers This iron meteorite was the first meteorite of any type ever found on another planet. The basketball-sized meteorite is rich in iron and nickel, and Opportunity found it in 2005. Hide Caption 14 of 21

Photos: Mars Opportunity and Spirit rovers Endurance Crater and its tendrils of sand presented a beautiful photo chance for the rover in 2004. Mars is full of dunes, and this is just one example Opportunity encountered. Hide Caption 15 of 21

Photos: Mars Opportunity and Spirit rovers These pointy features were called "Razorback." They're only a few centimeters tall, but the chunks of rock were found sticking up at the edge of flat rocks in Endurance Crater. They may have formed when fluids moved through rock fractures. Hide Caption 16 of 21

Photos: Mars Opportunity and Spirit rovers In 2010, Opportunity took this panorama of the eastward horizon view of Endeavour Crater's rim. Hide Caption 17 of 21

Photos: Mars Opportunity and Spirit rovers The Mars Spirit rover was Opportunity's twin, and it's mission ended in 2011. Both rovers featured a piece of metal with the American flag on the side. They are made of aluminum recovered from the site of the World Trade Center towers in New York City. Hide Caption 18 of 21

Photos: Mars Opportunity and Spirit rovers These two views from NASA's Curiosity rover -- from June 7, left, and June 10 2018 -- show how dust increased over three days from a major Martian dust storm that became planet-encircling on June 20, 2018. Opportunity was stranded in the middle of the storm and wasn't heard from afterward. Hide Caption 19 of 21

Photos: Mars Opportunity and Spirit rovers NASA's Opportunity rover appears as a blip in the center of this square. This image taken by HiRISE, a high-resolution camera on board NASA's Mars Reconnaissance Orbiter, showed the dust storm over Perseverance Valley had substantially cleared. Hide Caption 20 of 21