Our SpaceFlight Heritage: Curiosity’s fifth year on Mars marked by celebration – and song
NASA’s Curiosity rover celebrated 5 (Earth) years on Mars on Saturday, August 6. After launching on a United Launch Alliance (ULA) Atlas V 541 rocket on November 26, 2011, and then cruising through interplanetary space for nine months, the rover descended through the Red Planet’s atmosphere to the surface via its Skycrane system. Curiosity landed on Mars at exactly 05:17:57 SpaceCraft Event Time (SCET) UTC (1:17 a.m. EDT) on August 6, 2012.
At the time, Curiosity was the heaviest payload ever launched to the surface of Mars and required an entirely novel landing method. The rover still slowed itself from interplanetary speeds by aerobraking, protecting itself from the heat with a heat shield, then descended by parachute until the Skycrane activated.
The Sky Crane, NASA’s name for their innovative landing system, was a separate landing vehicle that used rocket thrust to hover over the surface of Mars, then lowered the Curiosity rover down to the surface via cables. After the rover touched the surface, the Sky Crane vehicle detached the cables and flew off to get away from Curiosity, crashing on the Martian surface some distance away a short time later.
The Curiosity rover itself carried a number of novel instruments and technologies to Mars. Curiosity was the first nuclear-powered rover on Mars, drawing its power from a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). Curiosity also carried the ChemCam, a geochemistry instrument that fires lasers at rocks to determine their chemical make-up. The CheMin instrument is the first X-ray diffraction analyzer on Mars and uses X-rays to determine the mineral content of samples. And the SAM instrument, for Sample Analysis at Mars, is the first wet chemistry instrument sent to Mars since the Viking probes.
While Curiosity is a technological marvel, and one of NASA’s flagship missions, that doesn’t mean that the robot has had smooth driving all the way. One of the most serious challenges the rover has faced is just driving. Curiosity’s wheels are machined from aluminum and include thin sections reinforced by grousers, thicker rib sections that support the thin sections and connect the surface of the wheel to the hub and motor. In 2013, engineers began to notice the wheels were wearing more quickly than had been expected.
Problems with the way the rover drove and with the unique terrain of Gale Crater and Mount Sharp were beginning to put holes in the thin sections of the wheels. Engineers eventually created new rules for driving the rover, avoiding certain kinds of terrain in their commanded drives and programming the rover itself to avoid those terrains when driving autonomously.
But engineers believed that as long as no grousers broke, the wheels would remain functional. In early 2017 engineers noticed some grousers beginning to break, but continued to believe the wheels would be fine for several years. They also adjusted the rover’s driving algorithms to put less stress on the wheels when climbing over rocks.
Despite these challenges, Curiosity has made powerful discoveries, some of which lead scientists to believe that Gale Crater may have hosted habitable conditions for potentially millions of years.
Engineers have also programmed the rover to be more autonomous. The rover can now select targets for its ChemCam instrument on its own and relay the results back to Earth. The rover can also chart its own path to destinations chosen by its human controllers.
The rover has driven 10.57 miles (17.01 kilometers) in total since its landing and has endured the harsh conditions of Mars for over 1700 sols (Martian days).
While August 6 was Curiosity’s fifth Earth-year on Mars, it has only been two and two-thirds in Martian years.
The roughly one-ton rover is just now preparing to resume science operations after the solar conjunction – the time when the Sun is between Earth and Mars – forced operations to pause after July 14.
NASA plans to build on Curiosity’s success with its Mars 2020 rover, which shares much of Curiosity’s design but with some improvements, such as stronger wheels, a drill for taking sample cores, and a system for leaving sample caches behind for future explorers. NASA is currently working to select a landing site, with the launch date expected to be sometime in July/August 2020 and the landing sometime in February 2021.
So how does the rover mark its birthday every year? As was noted on the aptly named Curiosity.com website, it uses its Sample Analysis at Mars (SAM) instrument to sing “Happy Birthday” to itself.
Video courtesy of NASA Goddard
Christopher Paul has had a lifelong interest in spaceflight. He began writing about his interest in the Florida Tech Crimson. His primary areas of interest are in historical space systems and present and past planetary exploration missions. He lives in Kissimmee, Florida, and also enjoys cooking and photography. Paul saw his first Space Shuttle launch in 2005 when he moved to central Florida to attend classes at the Florida Institute of Technology, studying space science, and has closely followed the space program since. Paul is especially interested in the renewed effort to land crewed missions on the Moon and to establish a permanent human presence there. He has covered several launches from NASA's Kennedy Space Center and Cape Canaveral for space blogs before joining SpaceFlight Insider in mid-2017.