Sagan discusses the story of the Heike crab and artificial selection of crabs resembling samurai warriors, as an opening into a larger discussion of evolution through natural selection (and the pitfalls of intelligent design). Among the topics are the development of life on the Cosmic Calendar and the Cambrian explosion; the function of DNA in growth; genetic replication, repairs, and mutation; the common biochemistry of terrestrial organisms; the creation of the molecules of life in the Miller-Urey experiment; and speculation on alien life (such as life in Jupiter's clouds). In the Cosmos Update ten years later, Sagan remarks on RNA also controlling chemical reactions and reproducing itself and the different roles of comets (potentially carrying organic molecules or causing the Cretaceous–Paleogene extinction event).

Beneath Jupiter's swirling clouds lie our solar system's deepest secrets: from its violent youth, through the birth of life to the death of the sun. Now, scientists are unlocking these secrets and discovering that every living thing exists thanks to Jupiter.

A look at the solar system's largest planet, Jupiter; its formation and composition and its mini-solar system of over 60 moons – some of which may have the potential to support extra-terrestrial life.

Chris Lintott and Maggie Aderin-Pocock report on the reaction to the dramatic announcement of the discovery of phosphine gas in the clouds of Venus, a gas that could be a sign of life. Venus remains an inhospitable and unlikely host. But if not Venus, where in the solar system is the best place to look for alien life? Chris and Maggie investigate the latest missions to Mars and the icy moons of Jupiter and Saturn. Away from the search for life, Pete Lawrencepreviews the best meteor showers of the year.

From the detection of gravitational waves generated in space over a billion years ago, to discoveries in genetics here on Earth, we've collected the most compelling science breakthroughs and advances of 2016. Thanks to magnificent, hard-working scientists and researchers around the world, science keeps marching ever forward. And this year saw some discoveries that are absolutely brimming with the promise of greater discoveries, breakthroughs and quality of life in the future.

Does life exist on other planets? Astrobiology is a visionary new science that searches for life in space by combining the disciplines of astronomy, biology and geology. How did life evolve on Earth? What will life look like on other planets? These and other pertinent questions will be answered by a diverse group of scientists. Viewers will visit the Pilbara region of West Australia where the oldest evidence of life on Earth has been discovered. Travel to the moons of Jupiter and Saturn to test a theory that life could exist in the clouds of Venus. Finally, watch as experiments are done to see if life exists on exoplanets, earth-like planets beyond our solar system.