The Mars Science Laboratory and its rover centerpiece, Curiosity, is the most ambitious Mars mission yet flown by NASA. The rover's primary mission is to find out if Mars is, or was, suitable for life. Another objective is to learn more about the red planet's environment.
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Curiosity's extensive size allows it to carry a host of scientific experiments that will be able to zap, analyze and take pictures of any rock within reach of its 7-foot (2 meters) arm. Curiosity is about the size of a small SUV. It is 9 feet 10 inches long by 9 feet 1 inch wide (3 m by 2.8 m) and about 7 feet high (2.1 m). It weighs 2,000 pounds (900 kilograms). Curiosity's wheels have a 20-inch (50.8 cm) diameter.
Engineers at NASA's Jet Propulsion Laboratory designed the rover to roll over obstacles up to 25 inches (65 centimeters) high and to travel about 660 feet (200 meters) per day. The rover's power comes from a multimission radioisotope thermoelectric generator, which produces electricity from the heat of plutonium-238's radioactive decay. The power supply should last a full Martian year (687 Earth days) or more.
A complicated landing
The $2.5-billion MSL spacecraft launched from Cape Canaveral, Florida, on Nov. 26, 2011, and arrived on Mars on Aug. 6, 2012, after a daring landing sequence that NASA dubbed "Seven Minutes of Terror." Because of Curiosity's weight, NASA determined that the past method of using a rolling method with land bags would probably not work. Instead, the rover went through an extremely complicated sequence of maneuvers to land.
From a fiery entry into the atmosphere, a supersonic parachute needed to deploy to slow the spacecraft down. NASA officials said the parachute would need to withstand 65,000 pounds (29,480 kg) to break the spacecraft's fall to the surface.
Under the parachute, MSL let go of the bottom of its heat shield so that it could get a radar fix on the surface and figure out its altitude.
The parachute could only slow MSL to 200 mph (322 kph), far too fast for landing. To solve the problem, engineers designed the assembly to cut off the parachute, and use rockets for the final part of the landing sequence.
About 60 feet (18 m) above the surface, MSL's "skycrane" deployed. The landing assembly dangled the rover below the rockets using a 20-foot (6 m) tether. Falling at 1.5 mph (2.4 kph), MSL gently touched the ground about the same moment the skycrane severed the link and flew away, crashing into the surface.
NASA personnel tensely watched the rover's descent on live television. When they received confirmation that Curiosity was safe, engineers pumped fists and jumped up and down in jubilation.
News of the landing spread through social media, such as Twitter and Facebook, and traditional outlets such as newspapers and television. One engineer became famous because of the Mohawk he sported on landing day.
Primary mission: Can, or could, Mars support life?
Curiosity's prime mission is to determine if Mars is, or was, suitable for life. While it is not designed to find life itself, the rover carries a number of instruments on board that can bring back information about the surrounding environment.
Scientists hit something close to the jackpot in early 2013, when the rover beamed back information showing that Mars had habitable conditionsin the past. Powder from the first drill samples that Curiosity obtained included the elements of sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon, which are all considered "building blocks" or fundamental elements that could support life. While this is not evidence of life itself, the find was still exciting to the scientists involved in the mission.
"A fundamental question for this mission is whether Mars could have supported a habitable environment," stated Michael Meyer, lead scientist for NASA's Mars Exploration Program. "From what we know now, the answer is yes."
Tools for finding clues to life
The rover has a few tools to search for habitability. Among them is an experiment that bombards the surface with neutrinos, which would slow down if they encounter hydrogen atoms: one of the elements of water.
Curiosity's seven-foot arm can pick up samples from the surface and cook them inside the rover, sniffing the gases that come out of there and analyzing them for clues as to how the rocks and soil formed.
The Sample Analysis of Mars instrument, if it does pick up evidence of organic material, can double-check that. On Curiosity's front, under foil covers, are several ceramic blocks infused with artificial organic compounds.
Curiosity can drill into each of these blocks and place a sample into its oven to measure its composition. Researchers will then see if organics appear that were not supposed to be in the block. If so, scientists will likely determine these are organisms hitchhiking from Earth.
High-resolution cameras surrounding the rover take pictures as it moves, providing visual information that can be compared to environments on Earth. This was used when Curiosity found evidence of a streambed, for example.
Second mission objective: Check out the environment
Besides hunting for habitability, Curiosity has other instruments on board that are designed to learn more about the environment surrounding it. Among those goals is to have a continuous record of weather and radiation observations to determine how suitable the site would be for an eventual human mission.
Curiosity's Radiation Assessment Detector runs for 15 minutes every hour to measure a swath of radiation on the ground and in the atmosphere.
Scientists in particular are interested in measuring "secondary rays" or radiation that can generate lower-energy particles after it hits the gas molecules in the atmosphere. Gamma rays or neutrons generated by this process can cause a risk to humans.
Additionally, an ultraviolet sensor stuck on Curiosity's deck tracks radiation continuously.
The Rover Environmental Monitoring Station measures the wind's speed and chart its direction, as well as determining temperature and humidity in the surrounding air.
The rover is slated to last for at least the next two years, but some commentators say given the longevity of the Spirit and Opportunity missions, Curiosity could be around for the better part of a decade.
Curiosity ran into its first major problem in February 2013, when a computer glitch punted the roving laboratory into safe mode for a few days. The issue caused an interruption of normal science activities, but did not impact the rover's long-term health.
NASA hopes Curiosity will have the chance to climb Aeolis Mons (NASA nicknames it "Mount Sharp"), a 19,000-foot (6,000 m) mountain near the landing site, before the mission's end.
— Elizabeth Howell, SPACE.com Contributor