On Saturday, a car-sized rover named Curiosity rocketed off to Mars to seek further clues to that tantalising question — is there life out there? At the turn of the last century, there were fanciful ideas of a sophisticated Martian civilisation capable of digging vast systems of canals. But the Mariner spacecraft that flew past and orbited Earth's neighbour as well as the two Viking landers that touched down on its surface in 1976 sent back images of a cold, bleak, and barren land, with a thin atmosphere that was mostly carbon dioxide and no signs of life. However, missions to the planet since the 1990s have raised exciting possibilities that scientists are eager to explore. There are indications that Mars was once a wetter, perhaps even warmer, place. Water may have flowed on its surface and could still exist below the surface. Life could have arisen there and may be clinging on in some niches, such as underground springs warmed by volcanoes. Such life could take the form of hardy microbes.
Curiosity, NASA's Mars Science Laboratory, is expected to complete its 567-million-kilometre journey to the Red Planet in August 2012. A complicated and perilous descent will follow to set the 900-kg, six-wheeled rover on the floor of the large Gale crater. The rover, equipped with a suite of 10 scientific instruments, is the most sophisticated explorer sent to another planet. The experiments it will carry out are not, the U.S. space agency says, intended to “detect active processes that would signify present-day biological metabolism.” Nor would it try to image micro-organisms or their fossil remains. Rather, its task will be to find out if conditions favourable for life existed on the planet. It will seek additional evidence of water and how the Martian climate might have changed over time. A layered mountain at the centre of the crater, with minerals that form in water, might provide a wealth of information about such changes. The rover will also look for organic molecules, a further sign that life could have arisen there. It will examine whether the traces of methane found in the atmosphere could have a biological origin. In addition, it will try to establish the various energy sources that life forms could utilise. Down the road, what scientists would really like is a mission to bring back Martian soil and rock samples for detailed analysis in the lab. But such a mission will be costly and stands little chance of being funded any time soon. So when it comes to understanding possibilities for life on Mars, it's over to Curiosity and the science it can do.