The winning entry was submitted by Clara Ma, a sixth-grade student from Sunflower Elementary School in Lenexa, Kansas. Curiosity's expense, estimated at more than $1 billion, as well as the two-year delay in its launch, led to the institution of stronger requirements to maintain baseline cost and baseline schedules for future missions. After launch by an Atlas V 541 (powered by a Russian RD-180 engine), MSL was delivered into a 165 × 324-kilometer orbit around Earth at 35.5° inclination. At 15:33 UT, the Centaur upper stage fired to send the payload—the cruise stage and MSL—on a trajectory to Mars. MSL used a unique entry, descent, and landing (EDL) profile, designed to accommodate for the fact that the Martian atmosphere is too thin for regular parachutes and standard aerobraking but too thick for deceleration with rockets. MSL's relatively heavy weight—much heavier than anything ever landed on Mars—presented engineers with some serious challenges. The EDL used by MSL was entirely autonomous without ground intervention and involved four separate stages: guided entry, parachute descent, powered descent, and sky crane landing, all of which took a total of only 7 minutes on 6 August 2012. The guided entry within the aeroshell was helped by small attitude control jets that narrowed the landing ellipse for MSL to a 20 × 7-kilometer area. Having slowed down to Mach 1.7, a supersonic parachute deployed (similar to those on Viking, Mars Pathfinder, and MER). The heat shield (from the aeroshell) was then discarded, and at about 1.8 kilometers altitude, with velocity down to 100 meters/second, the actual descent stage with Curiosity underneath it was released from the aeroshell, and eight variable thrust monopropellant hydrazine thrusters fired to slow the payload down further until Curiosity was slowly lowered from the descent stage with a 7.6-meter tether known as the sky crane system. The rover was then gently brought down to the surface at 05:17 UT on 6 August 2012. Just 2 seconds after the rover touched down, the sky crane/descent stage was freed and flew away and crashed about 650 meters away. Curiosity landed at Gale Crater, a 154-kilometer diameter impact crater estimated to be 3.5–3.8 billion years old. The precise landing coordinates are 4.5895° S / 137.4417° E. NASA named the landing site Bradbury Landing site after Ray Bradbury (1920–2012), author of The Martian Chronicles. On 15 August, Curiosity began initial instrument and mobility checks (including a test of the laser on a rock using the ChemCam instrument on 19 August). The rover began its first drive on 29 August, slowly taking about two months to cross about 400 meters east to a location named Glenelg. During the fall of 2012, Curiosity identified several interesting rocks that it investigated using both the MAHLI and APXS instruments. An area called "Rocknest" was also identified as an area to test out the scoop on the rover's remote arm. On 27 September 2012, NASA announced that Curiosity had found hints of an ancient streambed, indicating that there might have been a "vigorous flow" of water on Mars. On 27 October 2012, Curiosity conducted its first x-ray diffraction analysis of Martian soil, and on 3 December, NASA announced the results of Curiosity's first extensive soil analysis, which had revealed the presence of water molecules, sulfur, and chlorine. The small amounts of carbon detected could not be properly sourced and might have been from instrument contamination. More conclusively, in March 2013, NASA announced the data from the rover (based on an investigation of the so-called "John Klein" rock) suggested that Gale Crater was once suitable for microbial life. The result of further analysis showed the existence of water, carbon dioxide, sulfur dioxide, and hydrogen sulfide. In terms of rover operations, on 28 February 2013, the rover's active computer's flash memory developed a problem that made the computer reboot in a loop. As a result, controllers switched to the backup computer that became operational on 19 March. After drilling a rock in February, Curiosity drilled its second rock ("Cumberland") on 19 May 2013, generating a hole about 6.6 centimeters deep and delivering the material to its laboratory instruments. In early July 2013, Curiosity exited the Glenelg area and began a long trek to the mission's main destination, Mount Sharp. A long drive on 17 July of 38 meters meant that Curiosity had now traveled a total distance of 1 kilometer since it landed. As Curiosity continued toward Mount Sharp, NASA announced further findings. On 19 September 2013, scientists revealed that data from Curiosity of samples of the atmosphere taken six times from October to June 2012, confirmed that the Martian environment lacks methane, suggesting that there is little chance that there might be methanogenic microbial activity on Mars at this time. At the end of the year, on 7 November, the rover abruptly reverted to "safe mode" (apparently due to a software error) but controllers revived the vehicle within three days to resume nominal surface operations. Later, on 17 November, there was a spurious voltage problem that suspended work for a few days. By 5 December, the rover's ChemCam laser instrument had been used for more than 100,000 shots fired at more than 420 different rock or soil targets. Through the next few months, Curiosity returned many spectacular images (including of Earth in the Martian night sky). One image returned in April 2014 showed both Ceres and Vesta. In May 2014, Curiosity drilled into a sandstone slab rock ("Windjana"), the third time on its traverse, this time at a waypoint along the route towards the mission's long-term destination on the lower slopes of Mount Sharp. Curiosity passed its two-year mark on Mars on 5 August 2014, having already far exceeded its original objectives. In August 2014, Curiosity was about to make its fourth drilling experiment but mission planners decided not to at the last minute as it was thought that the rock ("Bonanza King") was not stable enough. Finally, on 11 September 2014, Curiosity arrived at the slopes of Mount Sharp (or Aeolis Mons), now 6.9 kilometers away from its landing point. In less than two weeks, on 24 September 2014, the rover's hammering drill was used to drill about 6.7 centimeters into a basal-layer outcrop on Mount Sharp and collected the first powdered rock sample from its ultimate target. Perhaps the most striking announcement of the mission was made on 16 December 2014, when NASA scientists announced that Curiosity had definitively identified the first instance of organic molecules on Mars. These were found in a drilled sample of the Sheepbed mudstone in Gale Crater. While these could be from organisms, it is more likely that the substance is from dust and meteorites that have landed on the planet.
This low-angle self-portrait of NASA's Curiosity rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin." Bright powder resulting from that drill, carried out on 30 July 2015, can be seen in the foreground. Credit: NASA/JPL-Caltech/MSSS
<!-- image -->This plaque on board Curiosity bears the signatures of several U.S. officials including that of then-President Barack Obama and Vice-President Joe Biden. The image was taken by the rover's Mars Hand Lens Imager (MAHLI) on 19 September 2012, the rover's 44th Martian day on the Red Planet. Credit: NASA/JPL-Caltech/MSSS
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At the same time, new data showed that there was a recent tenfold spike and then decrease in the abundance of methane—still very tiny—in the Martian atmosphere. Curiosity was visible in a photograph taken on 13 December 2014 by the HiRISE camera on board Mars Reconnaissance Orbiter (MRO); the image clearly showed the rover as it was examining part of the basal layer of Mount Sharp inside Gale Crater. A later image, from 8 April 2015, also showed Curiosity very clearly on the lower slope of Mount Sharp. In late January 2015, Curiosity used a new, low-percussion-level drilling technique to collect sample powder from a rock target called Mojave 2. Preliminary results (based on analysis by the CheMin instrument) suggested more acidic qualities in the form of jarosite, than previous drilled samples. On 24 February, Curiosity used its drill for the sixth time, this time to collect sample powder from inside a rock known as Telegraph Peak that was resting on the upper portion of Pahrump Hills (also the site for the two previous drilling experiments). Three days later, Curiosity experienced a so-called "fault-protection action" that stopped the robot from transferring sample material between devices because of an "irregularity" in the electric current. After a series of tests running through early March, mission planners finally directed the robotic arm to resume its work on 11 March and have it deliver the sample to the CheMin analytic instrument. Later in March, scientists published results (in the Proceedings of the National Academy of Science) from the SAM instrument suite that indicated for the first time the existence of nitrogen on the surface of Mars released during the heating of Martian sediments. The nitrogen, which NASA called "biologically useful" was in the form of nitric oxide, perhaps released from the breakdown of nitrates. The discovery added more weight to the argument that ancient Mars might have been "habitable for life." On 16 April, Curiosity passed the 10-kilometer mark on its travels as it moved through a series of shallow valleys between Pahrump Hills and Logan Pass, its next science destination. Curiosity resumed full operations after a period of limited activity for most of June when Mars passed nearly behind the Sun (relative to Earth). In late July, the rover found unusual bedrock in a target named Elk, one with unexpectedly high level of silica, which suggests conditions suitable for preserving ancient organic material. On 12 August 2015, Curiosity finally finished its work at Marias Pass, where it had been since May, and where it had drilled a rock target named Buckskin and found rocks with high silica and hydrogen content. It then headed upward and southwest up Mount Sharp. Much later, in June 2016, scientists published results from an investigation of Buckskin noting that the silica mineral in question was tridymite, a material generally linked to silicic volcanism. Continuing its studies at Mount Sharp, on 29 September 2015 Curiosity drilled its eighth hole (and fifth at Mount Sharp), one that was 65-mm deep in a rock known as Big Sky as part of an experiment to analyze Martian rocks in both the CheMin and SAM instrument suites. New results from Curiosity, published in October 2015, confirmed that billions of years ago there were definitely water lakes on Mars. Scientists determined that water helped deposit sediment into Gale Crater, and the sediment was deposited as layers that formed the foundation for Mount Sharp, the mountain in the middle of Gale. At the end of the year, in December 2015, Curiosity began close examination (and returned spectacular images) of dark sand dunes up to two stories tall, located at Bagnold Dunes, a band along the northwestern side of Mount Sharp. Through the subsequent few weeks, the rover took several samples from the Samib Dune, that were sorted by grain size for closer studies. Moving on from the dunes in early March, Curiosity climbed onto the Naukluft Plateau on the lower side of Mount Sharp, ending up in a stretch of extremely rugged and difficult-to-navigate terrain, whose bedrock was shaped by long periods of wind erosion into ridges and knobs. Here, the rover continued to take drill samples (its 10th and 11th). On 2 July 2016, Curiosity suddenly entered into safe standby mode, but controllers were able to return it to normal operations a week later. The cause of the original switch to safe mode was a software "mismatch" in a particular mode, involving writing images from some cameras' memories into files on the rover's main computer. Among the many thousands of images returned by Curiosity, some of the most spectacular were those of the Murray Buttes region of lower Mount Sharp. Color images showed beautiful vistas not unlike "a bit of the American desert southwest," according to Curiosity Project Scientist Ashwin Vasavada.