The episode, devoted to the planet Mars, begins with scientific and fictional speculation about the Red Planet during the late nineteenth and early twentieth centuries (H. G. Wells' The War of the Worlds, Edgar Rice Burroughs' science fiction books, and Percival Lowell's false vision of canals on Mars). It then moves to Robert Goddard's early experiments in rocket-building, inspired by reading science fiction, and the work by Mars probes, including the Viking, searching for life on Mars. The episode ends with the possibility of the terraforming and colonization of Mars and a Cosmos Update on the relevance of Mars' environment to Earth's and the possibility of a manned mission to Mars.

Professor Brian Cox fulfils a childhood dream by going behind the scenes at Nasa’s Jet Propulsion Laboratory (JPL), mission control for Mars 2020 – one of the most ambitious missions ever launched that may finally reveal if life ever existed on the red planet.
In 1980, a young Brian Cox wrote to JPL asking for photos from some of their missions to the planets. The pictures they sent him from Voyager and the Viking mission to Mars were a source of inspiration that set him on the path to becoming a physicist.
Now, over 40 years later, he has been granted privileged access to JPL, including key mission areas that are usually off-limits to film crews. Brian spends a week following the team who guide the Perseverance rover and the Ingenuity helicopter - the first powered aircraft ever sent to another planet - across the surface of Mars during a critical stage of the mission.
Perseverance’s goal is to search for signs of long extinct life on the surface of Mars in an area called Jezero Crater, which, 3.8 billion years ago, was filled by a vast lake. If it finds evidence of that life, it could change everything we know about life in the universe - and even transform our understanding of our own origins.

The planets of our solar system have experienced epic catastrophes throughout their long history, both raining down from outside and bubbling up from within. We'll voyage back in time to investigate the violent events that profoundly shaped the planets, including earth itself. We'll witness stunning revelations about what transformed Mars into a barren, hostile desert... The disaster that changed Venus from temperate to hellish... The impact that blew away Mercury's mantle, turning it into a planetary core... A colossal disturbance that rearranged the orbits of the gas giants... Titanic impacts on Jupiter... And how a lost moon may finally explain Saturn's rings.

This is the story of two of the biggest scientific breakthroughs of the 21st century, told by the incredible scientists who made them happen. The first is LIGO’s measurement of gravitational waves coming from a black hole merger, and the second, the Event Horizon Telescope’s image of a black hole.

Comet ISON can well be the brightest and most spectacular comet for a generation. It appeared above the eastern horizon from December 2013 as a glorious streak across the sky. ISON has been travelling towards the sun for ten thousand years and will make only one orbit through its corona before disappearing off into the outer solar system.
But as well as providing a great spectacle, ISON's tail of vaporised gas and water, hundreds of millions of kilometres long, will give insights into some of the greatest mysteries of science; it will help explain the origins of the solar system, whether earth's water was delivered on comets and even whether we are alone in the universe.

We think of comets as beautiful glowing balls of light streaking across our skies with their long sweeping tails, yet comets are so much more than just a cosmic firework display. Comets have a uniquely important place in modern science. As time machines from the early universe, they could hold the key to unlock the secrets of the cosmos. Comets could even be the origin of life itself. We follow the incredible odyssey of a comet as it sails through the solar system, watching it's every move as it evolves from a dormant chunk of ice and rock into a tumbling, violently active nucleus engulfed in a gaseous haze. What we learn is a revelation; comets are even more mysterious and fascinating than we had ever imagined.