The next important era in the exploration of the Red Planet began in August 2012 with the successful landing of NASA’s Mars Science Laboratory and its robot rover Curiosity. The Mars Science Laboratory mission is a technological trailblazer in several respects, not least because the Curiosity rover is the most ambitious exploratory tool ever placed on another world. If all goes according to plans, for at least the next two years Curiosity will explore intriguing geological formations in the Gale Crater region in a quest to determine whether Mars might once have had an environment more conducive to life than it does today. See also: Space flight, 2011
NASA has been exploring the surface of Mars for the past 15 years with a series of robotic Mars rovers: first the Sojourner rover of the Mars Pathfinder mission in 1997–1998, then the twin rovers Spirit and Opportunity of the Mars Exploration missions that landed in 2004. (Although the rovers were officially designed to last only for about 90 days, Spirit continued to send signals back to Earth until 2010, and Opportunity is still active on the Martian surface as of this writing.) The Curiosity rover far surpasses those. First, it is much larger: Sojourner was two feet long and weighed only 25 pounds, and Spirit and Opportunity are five feet long and weigh less than 400 pounds, Curiosity is 10 feet long and weighs 1984 pounds with its scientific instruments. Those instruments include a variety of cameras, drilling equipment, chemical sensors, and a laser that can vaporize rock for spectroscopic analysis of its contents. Data from the rovers can therefore add significantly to other observations made by orbiting craft, such as Mars Express, and stationary landers such as Phoenix. See also: Mars; Mars Express; Phoenix Mars mission; Space probe
Even the landing of Curiosity was a technical tour de force because it involved a maneuver called a sky crane, which NASA had never before attempted with a probe. To deposit Sojourner, Spirit, and Opportunity on the Martian surface, NASA had first used a parachute to slow the descent of the spacecraft, and then dropped the lander inside a cocoon of airbags that absorbed most of the impact. Because of Curiosity’s large mass, however, airbag materials would not have been sufficiently sturdy to work. Engineers at the Jet Propulsion Laboratory therefore designed an alternative system in which a platform flying on thruster rockers and holding the rover on its undercarriage dropped out of the parachuting spacecraft and made a guided descent to about 60 feet above the Martian surface. The platform then lowered the Curiosity rover to the ground on a tether (which reduced the amount of dusty that might be thrown onto its instruments) before fleeing from the landing site. Because this entire atmospheric entry and landing process would take only seven minutes but the distance between Mars and Earth imposed a 14-minute radio delay, the Mars Science Laboratory craft would need to execute all these maneuvers entirely on its own. In the weeks prior to the landing, NASA engineers took to referring publicly to the “seven minutes of terror” during which they would have no idea whether the mission had already crashed on the planet’s surface. Fortunately, the landing process worked exactly as planned.
Curiosity is now preparing to travel to the nearby foot of Mount Sharp, a large mountain in the center of the Gale Crater formation. Images from probes orbiting Mars suggest that the lower strata of Mount Sharp may consist of clays. If so, Curiosity’s analysis of the rocks in the formation should help to determine whether liquid water ever existed in any abundance on the surface of Mars, and could have helped to make the planet more habitable for some period in its past.