Doing the Rocker-Bogie Boogie
Curiosity sports the same rocker-bogie suspension system that carried previous Mars rovers Sojourner, Spirit and Opportunity over hill and Martian dale. The system, which employs neither axles nor springs, remains stable because each wheel can move up and down independently. Thanks to Martian gravity and clever Earthling engineering, the rover passively keeps all six wheels on the ground and constantly under load, even when clearing obstructions approaching 30 inches (75 centimeters). This balance of forces provides vital traction, particularly in soft, sandy environments. The flexible suspension can also "absorb" some of the tilt of inclines, thereby keeping the rover more level [sources: Harrington; JPL].
The "monster truck of science" isn't a nitro-burning, fire-breathing funny car, or a plain old internal-combustion gas-guzzler. Nor does it sport the solar panels that generated juice for its forerunners. No, on this mission, NASA went nuclear.
Curiosity pulls power from plutonium-oxide. As the radioisotope decays, it gives off heat, which the rover converts to electricity using thermocouples. This Multi‐Mission Radioisotope Thermoelectric Generator (MMRTG) will keep the rover's battery topped off with 110 watts of electrical power.
The system packs more power than the solar approach and has no moving parts to break, but can this generator outperform good old gallium-arsenide panels? After all, Spirit operated until the spring of 2010, and diehard Opportunity is still spinning its odometer, having racked up 21 miles (34 kilometers) at 328 feet (100 meters, roughly an American football field length) per day. These exceptional vehicles far exceeded their 90-day mission mandates, partly because of free, renewable, solar power.
Well, don't nuke the nuke just yet. The radioisotope system's 14-year life expectancy could outlast the rover itself, and will never fall victim to the whims of Martian weather, dust or winter [source: JPL]. Besides, the extra power is worth the tradeoff: Curiosity will cover more ground than its predecessors, traveling at roughly twice their speed. In the single Martian year (about 687 Earth days) of its initial mission, it will rack up 12 miles (19 kilometers) inside Gale Crater, carrying a scientific payload 10-15 times more massive than Spirit or Opportunity. Power will remain available all along, as will excess heat that Curiosity will use to keep its vital instruments warm [source: NASA].
Helping Curiosity put that horsepower to effective use is NASA's old-and-improved rover rocker-bogie chassis (see sidebar), an assembly of jointed titanium tubes attached to six aluminum wheels so thin they flex like rubber. All four corner wheels can rotate through 90 degrees, which enables the rover to turn in place. Engineers beefed up Curiosity's suspension somewhat to suit its new role as landing gear, and to accommodate a heftier vehicle that must cross more rugged terrain [sources: Harrington; JPL].
Shortly after landing, that chassis will cart the rover to its first destination: a rocky outcrop nicknamed "the fence." NASA targeted this crag because previous Mars observations revealed that it contains aqueous deposits -- minerals formed in water. From there, Curiosity will venture into canyons, rocky mountainsides and hill country reminiscent of Sedona, Arizona's red rocks, which also formed in a watery environment. By then, its first Martian year will have come and gone.
From there, the rover will delve into rockier and more rugged terrain. Exploring this area will require several years, but, once across, the rover's cameras will be treated to a panorama of the path Curiosity has traveled [source: NASA].
All along the way, the Mars Science Laboratory will investigate whether conditions exist, or have ever existed, that could support microbial life on Mars, and whether clues to such life remain preserved in Mars's rocks and soil.
Curious for more info on Mars and how to get there? Bump on over to the links on the next page.