artist's impression of Curiosity on Mars
The latest in a long series of Mars missions is due to launch at the end of the week – close to 40 years after the first Mars lander – Mars 3, which landed on Mars in December of 1971. Unfortunately Mars 3 landed in the midst of a vast sandstorm and only transmitted data for 14.5 seconds. Let’s hope for more from the next mission– the Mars Science Laboratory – a rover called Curiosity. Curiosity is about twice as long and more than five times as heavy as any previous Mars rover.
Landing a large mass on Mars is a difficult challenge. The atmosphere is both too thick and too thin. It is thick enough to prevent rockets alone from being used. Huge forces are involved when a rocket is used – causing shaking and twisting that would probably destroy a large vehicle. But, the atmosphere is too thin for parachutes and aerobraking alone to work. Although some previous missions have used airbags to cushion the shock of landing, Curiosity is too large for this to be an option. And airbags have not always worked – the Beagle2 lander from 2003 used airbags—it deployed from its orbiter and was not heard of again.
Curiosity will use a combination of techniques to get a soft landing. First, a large heat shield will slow it down significantly – and this heat shield has been designed to be steerable. It has small thrusters that allow it to be tilted as it moves through the thin Martian air. When the vehicle is 10 km above the surface a parachute will be released. This will slow the rover even more – down to a mere 100 m/s. At 2km above the surface the rover will drop out of the aeroshell and a set of rockets on a platform above it will fire. The rover will finally be lowered down to the surface from a sky crane hanging beneath the platform. This rather unusual descent method has not been used in a landing yet.
The landing area chosen for Curiosity is Gale crater. This large crater has a mountain in the middle and an alluvial fan – a feature definitely associated with water on Earth. But Curiosity will go beyond the “follow-the-water” strategy of recent Mars exploration. The rover’s science payload can identify organic compounds – the other ingredients of life. It is hoped that layers of clay at the bottom of Gale’s mountain contain minerals that have latched onto organic compounds and preserved them.
The rover will use a plutonium fuel source, producing 125 W of electrical power. This will keep Curiosity warm in the cold Martian environment for years, although the prime mission is designed to run for 2 years. Given that the last two rovers, Spirit and Opportunity were set up to run for 3 months, and one is still going 7 years later – we can hope for an extended run of data – if it lands successfully next August.
Listen live to What is the Stars? on lyricfm, Mondays and Fridays at 22:45
First broadcast week of November 21, 2011. Curiosity launched successfully on November 26, 2011!