Julian Richards investigates the impact of the Vikings in Britain. This edition focuses on the archaeological trail left by the Vikings as they travelled from Norway along the sea road to Dublin. Settlements, a boat burial and evidence of trading have been discovered on the Scottish isles, and silver hoards found in Ireland suggest that Dublin was not only wealthy and important, but also a centre for trade in slaves.

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 story of the Viking world's most famous warrior, the legend of Beowulf is the ultimate tale of courage. Pit against thirsty invaders, barbaric monsters and a fire breathing dragon, Beowulf emerges as Norse mythology's greatest hero. But could this warrior have actually been real? Unearthed burial mounds and ancient carvings suggest the myth of Beowulf might have been more than epic legend.

The third assault on the tattered remains of Roman civilization came from even further North, where the melting glacial ice had created immense sheltered fjords, leaving its inhabitants little choice but the sea. These fearless navigators understood that dominion over the oceans was the key to their ambitions.
Where the Romans expanded incrementally, the Vikings adopted a bolder, more aggressive approach. So was it the Dark Age which failed Europe, or the stifling uniformity of the great Roman experiment? Were the lost tribes more victim than failure? Richard Rudgley will hope to shed new light on the real secrets of the so-called Dark Age.

This episode covers the nature of how life may have developed on Earth and the possibility of life on other planets. Tyson begins by explaining how the human development of writing systems enabled the transfer of information through generations, describing how Princess Enheduanna ca. 2280 BCE would be one of the first to sign her name to her works, and how Gilgamesh collected stories, including that of Utnapishtim documenting a great flood comparable to the story of Noah's Ark. Tyson explains how DNA similarly records information to propagate life, and postulates theories of how DNA originated on Earth, including evolution from a shallow tide pool, or from the ejecta of meteor collisions from other planets. In the latter case, Tyson explains how comparing the composition of the Nakhla meteorite in 1911 to results collected by the Viking program demonstrated that material from Mars could transit to Earth, and the ability of some microbes to survive the harsh conditions of space. With the motions of solar systems through the galaxy over billions of years, life could conceivably propagate from planet to planet in the same manner. Tyson then moves on to consider if life on other planets could exist. He explains how Project Diana performed in the 1960s showed that radio waves are able to travel in space, and that all of humanity's broadcast signals continue to radiate into space from our planet. Tyson notes that projects have since looked for similar signals potentially emanating from other solar systems. Tyson then explains that the development and lifespan of extraterrestrial civilizations must be considered for such detection to be realized. He notes that civilizations can be wiped out by cosmic events like supernovae, natural disasters such as the Toba disaster, or even self-destruct through war or other means, making probability estimates difficult. Tyson describes how elliptical galaxies, in which some of the oldest red dwarf stars exist, would offer the best chance of finding established civilizations. Tyson concludes that human intelligence properly applied should allow our species to avoid such disasters and enable us to migrate beyond the Earth before the Sun's eventual transformation into a red giant.