The space exploration era started on 4th October 1957, when the satellite Sputnik was launched into orbit by the (then) USSR. This small spacecraft (about 60cm in diameter) circled the Earth for three months, sending back signals for only 2 weeks before its batteries died. It had no scientific instruments on board, yet the results from its flight served to influence the course of space (and political) history, leading eventually to the Apollo astronauts and footsteps on the lunar surface. Now, fifty years after Sputnik, we are set to begin a new era of space exploration. Fourteen of the world’s space-faring nations have signed an accord: the Global Exploration Strategy, which is designed to ensure a peaceful, co-operative and international effort to reach out from the Earth and explore our local neighbourhood.

So what have we learnt about the Solar System in the last 50 years, and what are the questions which remain to be answered through space exploration? What will the next 50 years bring? Can our goals be achieved through robotic exploration alone, or will astronauts once again walk on the Moon? And is the idea of a human base on Mars an impossible dream?

Monica Grady is Professor of Planetary and Space Sciences at the Open University in Milton Keynes and a Scientific Associate of the Natural History Museum in London. Monica received an honours degree in Chemistry and Geology from Durham University in 1979, then a Ph.D. from Cambridge University in 1982. Her particular research interests are in primitive and martian meteorites, interstellar components in meteorites, micrometeorites, and astrobiology and the possibilities of life beyond Earth. Asteroid (4731) was named “Monicagrady” in her honour. In 2003, Monica gave the Royal Institution Christmas lectures on the theme ‘Voyage in Space and Time’.