NASA's Curiosity Mars Rover used two cameras to take this selfie in front Mont Mercou (a rock outcrop that is 20 feet tall)NASA's Curiosity Rover has been on Mars since 1999.The robot, which was about the size of a car, launched in November 2011 to touch down inside Mars' Gale Crater (96 miles wide, 154 kilometers) on Aug. 5, 2012. (The Curiosity landing took place on Aug. 6, Eastern Time, but it was still August 5, 2012 in California, where NASA's Jet Propulsion Laboratory manages the mission.Curiosity has helped scientists understand Mars' past habitability, as well as how it has changed over the years. The rover's observations showed that Gale had a lake and stream system in its ancient past. This could have been capable supporting Earth-like life for millions upon millions of years.Similar: Amazing Mars photos taken by NASA's Curiosity RoverCuriosity made its way to Mount Sharp in September 2014. It rises 3.4 miles (5 km) above the Red Planet's center. The six-wheeled robot began climbing up the steep, sloped massif, reading the rock layers as the climb progressed.These layers contain a history about Mars' climate over time. It has changed from being relatively warm and humid to becoming cold and bone dry. Curiosity now has the data it needs to shed light on this shift.Nearly reached Mount Sharp, the rover found sulfate-bearing rock deposits that are indicative of a dry environment. Curiosity found clays on all the slopes it has studied so far. Clays form when there is liquid water.The September 2016 self-portrait by NASA's Curiosity Mars Rover shows the vehicle at the Quela drilling site in the scenic Murray Buttes region on lower Mount Sharp. This panorama was created from multiple images taken with the MAHLI camera at one end of the rover’s arm. (Image credit: NASA/JPL-Caltech/MSSS)Curiosity made many other interesting discoveries while on Mars. Curiosity has also discovered organic chemicals, which are the carbon-containing building blocks that make up life as we know. The rover also detected spikes in methane concentrations, which is a gas that is mainly generated by living organisms.However, methane can also come from abiotic processes. The source of the gas in Gale Crater is still a mystery.Curiosity has covered 16.14 miles (25.98 kilometers) in nine years of its existence on Mars. Its odometer is likely to continue ticking over for some time. Mission team members claim that the rover is still in good health, despite its advanced age. The nuclear power system of its nuclear reactor is designed to last at least 14 years. All discussion of years in this story is about Earth years. Mars years last longer and each one takes 687 Earth days.Curiosity is not the only robot on Mars. NASA's InSight lander is listening for Marsquakes ever since November 2018. NASA's Perseverance Rover landed in the Jezero Crater, which measures 28 miles (45 km) across.Perseverance is heavily modeled on Curiosity and is currently searching for signs of ancient Mars life. Perseverance flew to Mars aboard the Ingenuity helicopter (weighing in at 1.8 kgs), which has already made 10 flights inside Jezero.There's also the Zhurong Rover, which is part Tianwen-1's first China-made Mars mission. Zhurong, which landed on May 14th, kicked off a three-month-long surface mission.Mike Wall is the author and illustrator of "Out There" by Grand Central Publishing (2018). This book is about the search for alien life. Follow him @michaeldwall. Follow us on Facebook @Spacedotcom and Twitter @michaeldwall
