Naturalist Sir David Attenborough investigates whether the world is heading for a population crisis. In his lengthy career, Sir David has watched the human population more than double from 2.5 billion in 1950 to nearly seven billion. He reflects on the profound effects of this rapid growth, both on humans and the environment. While much of the projected growth in human population is likely to come from the developing world, it is the lifestyle enjoyed by many in the West that has the most impact on the planet. Some experts claim that in the UK consumers use as much as two and a half times their fair share of Earth's resources. Sir David examines whether it is the duty of individuals to commit not only to smaller families, but to change the way they live for the sake of humanity and planet Earth.

The intriguing possibility of life on Mars has fuelled man's quest to visit the Red Planet. Drawing on 45 years of Horizon archive, space expert Dr Kevin Fong presents a documentary on Earth's near neighbour. Man's extraordinary attempts to reach Mars have pushed technological boundaries past their limit and raised the tantalising prospect of establishing human colonies beyond our own planet.

Professor Brian Cox takes a look through nearly 50 years of BBC archive at the story of man's relationship with the moon. From the BBC's space fanatic James Burke testing out the latest Nasa equipment to 1960s interviews about the bacon-flavoured crystals that astronauts can survive on in space, to the iconic images of man's first steps on the moon and the dramatic story of Apollo 13, Horizon and the BBC have covered it all.

But since President Kennedy's goal of landing a man on the moon before the end of the 1960s was reached, no-one has succeeded in reigniting the public's enthusiasm for space travel and lunar voyages. Why? On his journey through the ages, Professor Cox explores the role that international competition played in getting man to the moon and asks if, with America no longer the world's only superpower, we are at the dawn of a bright new space age.