The Planets

Different Worlds reveals the planetary enigmas on our doorstep and embarks for the final voyage to the only planet still to be visited by a spacecraft – Pluto. Will our encounter with this tiny ball of ice and rock and the trillions of icy objects beyond it paint a clearer picture of how the planets came to be?

At first we were alone on Earth, living in the shadow of the volcano and in fear of the earthquake. We watched Mars and Venus wander in the night sky, and wondered if the ground on those worlds shook and spat fire. Would these planets share our landscapes of mountains and valleys, of continents drifting across oceans of magma? This is the story of the pioneering missions to our neighbouring worlds, of our first glimpses of their awe-inspiring terrains. From the giant lava plains of Venus to the volcanoes on Mars that dwarf Mount Everest,Terra Firma takes us on a journey of exploration around the rocky planets and on to the distant icy moons of Jupiter, Saturn and beyond.

For centuries the giant planets floated on the fringes of the solar system as distant objects in the eyepieces of astronomers. But in December 1973 mankind had its first close encounter with Jupiter. This episode charts the story of our discovery of these massive planets, from Galileo’s sighting of Jupiter's moons in 1610 to JPL's journeys to Uranus and Neptune nearly 400 years later. It explores the role the giant planets played in shaping the vast disk of stellar debris into the solar system we know today. Rings to radiation belts, moons to magnetospheres, each gas giant is at the heart of a solar system in miniature, revealing its secrets to only the boldest missions.

Nothing could be more familiar to human eyes than the Moon; yet nothing could be stranger. None of our near neighbours in the solar system – Mercury, Venus or Mars – has a moon like ours, a companion in space so large that it rules our nights, our months, our ocean tides. Why Earth should have such a moon is one of the deepest mysteries of the Solar System. Moon tells the story of how the Earth’s satellite became the object of desire of the two Cold War superpowers, and how scientists jumped on the political bandwagon to solve the riddle of the century.

It was the Sun as no other human being had ever seen it before.The astronauts on board Skylab saw the blindingly bright disk, clearly visible, floating in the blackness of space. For millennia humans have always seen our star through the Earth’s atmosphere, but the Space Age has given us a new perspective that has revealed the many faces of the Sun and forced us to redefine it.We have now seen it in X-rays, ultraviolet/visible light, heat, and radio. But we have also discovered that the planets orbit inside the Sun. Star reveals the recently discovered inner secrets of this colossal engine that runs like clockwork, and shows how the planets struggle against the Sun’s invisible influence: the solar wind.

It is December 1971 and Soviet scientists are bracing themselves for an encounter with Mars at twenty-five thousand kilometres an hour. Mars 2 and 3 are their most advanced probes to date, and if all goes well they will steal for the Soviet Union the first ever pictures from the surface of another planet. But things look bleak for these robotics pioneers. Reports from telescopes across the country are pouring in to the Crimean control centre, all bearing the grim news of a giant storm on Mars. The planet is covered from pole to pole in a thick blanket of dust. But there is no reprogramming the probes – they are going in, storm or no storm. Despite the huddle of scientists around the receiving screens willing it to work, that glorious first picture is nothing more than a fuzzy mess of squiggles. The probe is dead. Mankind’s first contact with the atmosphere of Mars is over, and the welcome was anything but warm.