Earth: Feb 13

“Atmosphere”, this week’s episode of Earth is the penultimate in the series.

This episode tells the almost implausible story of how our world went from a barren rock with a sky of endless black, to the planet we know today, cloaked in the thin blue line of our life-sustaining atmosphere. When Earth first formed from clouds of dust and gas 4.6 billion years ago, it was – like so many other lifeless worlds in the universe – devoid of an atmosphere, an inhospitable rock floating in the black void of space.

But as the young planet was pummelled by asteroids a period of extraordinary upheaval began. Over a 2-billion year period, the planet faced violent eruptions and a toxic orange haze, vast oceans of water in the sky and seas turning rusty red. Until eventually, with the emergence of life and photosynthesis recalibrating the gases in our atmosphere, the stage was set for Earth to become the vibrant azure-skied planet we call home today.