By Bob Duncan
NASA’s latest, largest and most ambitious interplanetary probe, the Curiosity Rover, has landed safely on the surface of Mars at just after 6:30 am GMT, after a journey of more than 350 million miles.
The probe, which was launched in November last year from Cape Canaveral in Florida, cost over 1.5 billion pounds and is NASA’s most complicated robotic mission ever. It carries a scientific payload of 10 separate instruments and is powered by a multi-mission radioisotope thermoelectric generator (mini nuclear reactor) and lithium-ion batteries.
After its 254 day journey from earth, the Mars Science Laboratory spacecraft entered the Martian atmosphere, travelling at 13,200 miles per hour. The rover’s thrilling descent through the Martian atmosphere was so complex that it has been nicknamed “the seven minutes of terror.”
On entering the atmosphere, the craft turned so that its heat shield, the largest ever built, could protect the rover as it was slowed to a tenth of its former velocity by the thin Martian atmosphere. During this period the craft used jets to adjust its trajectory and ensure that it remained on course.
It then released a 16m supersonic parachute, at an altitude of about 7 miles and a velocity of around 900 mph. 24 seconds later, the heat shield was jettisoned and dropped away.
Some 85 seconds later, about a mile above the surface, the parachute separated. The craft, then travelling at about 180 mph, started its retrorockets and entered the powered descent phase. These reduced the lander’s velocity to less than 2 mph as it descended until it was about 20 metres above the landing site.
At this point, 4 of the 8 engines shut off and the rover was lowered from the rest of the lander, known as the “sky crane”, on nylon cords. The rover’s wheels and suspension, which doubled as landing gear, descended and locked into place just before the rover touched the surface of the planet.
As soon as the rover had landed, the sky crane was rocketed away to land elsewhere and the surface mission began.
The landing site was 4.6 degrees south latitude, 137.4 degrees east longitude, near the base of Mount Sharp inside the Gale Crater, and can be looked up on Google Mars.
The Mars Science Laboratory mission will assess whether the area Curiosity Rover explores has ever been a potential habitat for Martian life. The primary mission is intended to last for one Martian year, which is just under 2 Terran years long (98 weeks).
The mission will study whether the Gale Crater area of Mars has evidence of past and present habitable environments. These studies will be part of a broader examination of past and present processes in the Martian atmosphere and on its surface.
The rover will search for water and carbon molecules and will also check for other chemical elements important for life, such as nitrogen, phosphorus, sulphur and oxygen.
The research will use 10 instrument-based science investigations. The mission’s rover, Curiosity, carries the instruments for these investigations and will support their use by providing overland mobility, sample-acquisition capabilities, power and communications.
The payload includes mast-mounted instruments to survey the surroundings and assess potential sampling targets from a distance; instruments on Curiosity’s robotic arm for close-up inspections; laboratory instruments inside the rover for analysis of samples from rocks, soils and atmosphere; and instruments to monitor the environment around the rover.
In addition to the science payload, engineering sensors on the heat shield will gather information about Mars’ atmosphere and the spacecraft’s performance during its descent through the atmosphere.
To make best use of the rover’s science capabilities, a diverse international team of scientists and engineers will make daily decisions about the rover’s activities for the following day.
Mars is currently around 154 million miles from Earth, and signals from the rover take almost 14 minutes to reach us. The landing time of 05:31 GMT is “Earth received time”, the lander having actually touched down 14 minutes earlier.
The rover itself is 3 meters long (not counting its robot arm) by just under 3 meters wide and stands 2 meters tall. It has 6 individually controllable and steerable wheels and weighs a total of 900 kg, including its 75 kg science payload.
Mars itself is the fourth planet in the Solar system and is around half the size of the earth, or around twice the size of the moon. It has a very thin atmosphere of mainly carbon dioxide and has gravity about a third of the earth’s. It is about half again as far from the Sun as the Earth.
Watch a live feed of the Rover landing here: