In a magnificent feat of engineering and science, humanity’s latest probe to Mars landed successfully at about 07.30 South African time on Monday morning, next to a 5-km-high mountain and within the 150-km-diameter Gale Crater, which lies just south of the Red Planet’s equator.
The US National Aeronautics and Space Administration’s (Nasa’s) latest and biggest robot rover, the 1-t-mass Curiosity, used both a parachute and a rocket-powered descent stage to make its touchdown.
Curiosity made the trip from Earth to Mars encased in a protective shell and the atmospheric entry and landing process started with the enclosed rover separating from the spacecraft – known as the cruise stage – which had carried it the 570-million kilometres to the Red Planet. (The cruise stage then fell into the Martian atmosphere and burned up.)
The probe then entered the atmosphere, protected from the scorching heat by a heat shield. Once past the worst, and decelerated by the thickening atmosphere, the machine engaged in some hypersonic aeromanoeuvreing before deploying its parachute. The heat shield (which formed the lower part of Curiosity’s protective shell) was then jettisoned.
A radar system was then activated, using six radar beams to accurately measure altitude and speed. At an altitude of 1 600 m, the upper part of the protective shell, with the parachute still attached, was also jettisoned, to drift away and land elsewhere.
The rocket-powered descent stage, to which Curiosity was attached, then fired its motors to carry out a powered descent to achieve a soft landing. This was called the Sky Crane manoeuvre. As the descent stage approached the surface, it lowered Curiosity on cables and a communications umbilical, each 7.5 m in length. This system was adopted to allow the rover to make a soft landing directly on its own wheels, without any need for extra cushioning.
When Curiosity touched down, the descent stage noted the sudden loss of weight it was bearing, cut the cables and umbilical, and flew away to land or crash anywhere from 150 m to 300 m away from the rover.
The entire entry and landing process took seven minutes, dubbed (in advance) the Seven Minutes of Terror. “The Seven Minutes of Terror has turned into the Seven Minutes of Triumph,” enthused Nasa Associate Administrator for Science John Grunsfeld. “My immense joy in the success of this mission is matched only by overwhelming pride I feel for the women and men of the mission’s team.”
Curiosity has six wheels and is twice as long and five times as heavy as Nasa’s previous Mars rovers, the brilliantly successful Spirit and Opportunity. Curiosity is equipped with ten scientific instruments, whose combined mass is 15 times greater than that of the science payloads on each of Spirit and Opportunity.
The new rover’s instruments include a robotic arm fitted with a “hand” or turret at its end; that turret is equipped with a drill, a brush (to remove dust) a scoop to pick up soil, a camera for close-up views and two scientific instruments to help determine if Mars ever had conditions that would have allowed microbial life. Curiosity also has automated miniature laboratories which can analyse powered samples collected by the scoop.
It has a mast-mounted camera and laser turret, which mounts seven of its 17 cameras, which gives a human-scale view and serves for remote sensing. The laser will be fired at interesting rocks to vaporise a tiny part of them; this vapour then being analysed to determine whether they are worth closer analysis.
Curiosity’s primary mission is to determine if the right conditions to support life ever existed on Mars. The central mountain in Gale Crater has many layers of different rocks, making examination and analysis relatively easy. The Curiosity mission is being managed by the Jet Propulsion Laboratory, which is both a Nasa laboratory and a division of the California Institute of Technology.