MISSIONS TO THE RED PLANET
* 1976: Viking probes land on Mars. They show a dry, desolate terrain colder than Antarctica and drier than the Sahara. Life thought to be impossible.
* 1996: Nasa scientists analyse Martian meteorite ALH84001 which was recovered from the Antarctic ice cap. They conclude that it shows fossilised signs of life that may have existed on Mars 3.6 billion years ago. Other scientists dispute the interpretation.
* 2003: Beagle-2, a British-built probe, arrives on Mars but disappears during its descent to the planet’s surface. It contained a package of instruments that could have searched for chemical evidence of life.
* 2004: Nasa’s twin rovers, Spirit and Opportunity, land on Mars. ESA scientists confirm that abundant bodies of water once existed on the planet. They also find traces of methane gas, which could be a by-product of living organisms, or the result of volcanic activity.
* 2011: Aurora mission launched which will land a robotic rover on Mars in 2013. Nasa also plans two additional rovers to look for signs of life.
* 2016: An ambitious mission to return rock samples of Mars to Earth is due to be launched. This could confirm whether or not simple life forms have ever existed on Mars.
* 2030s: The first manned missions to Mars could take place as a joint project between the major developed countries of the world. It would be the first time that humans set foot on another planet.