NASA chief scientist predicts new rovers will find life on Mars within two years

NASA unveiled designs of its new Mars Rover which will embark on a mission to find signs of life on the planet in 2020. [Courtesy]

NASA's chief scientist Jim Green has predicted that life will be discovered on Mars within a couple of years - but warned that the world is not prepared.

The US space agency and the European Space Agency (ESA) are both preparing to send rovers to Mars next year, in search of alien life.