Brian Cox looks at our attempts to answer one of the most profound questions we can ask – are we alone in the universe? With scientists sending space probes to the furthest reaches of our solar system and beyond, the scientific search for alien life has begun. Inspired by a childhood love of science fiction, Brian still hopes to hear from ET. In this film, he explains why this search deserves to be taken seriously, and he explores the chances of it happening.

Humans have long gazed up at the night sky, wondering whether other lifeforms and intelligences could be thriving on worlds far beyond our own. But over the last few decades, ultra-sensitive telescopes and dogged detective work have transformed alien planet-hunting from science fiction into hard fact. We expected to find worlds similar to the planets in our own solar system, but we instead discovered a riot of exotic worlds. Vivid animation based on data from the most successful planet hunter of them all, the Kepler space telescope, brings these worlds into view: puffy planets with the density of polystyrene, unstable worlds orbiting two suns and 1,000-degree, broiling gas giants with skies whipped into titanic winds.
But perhaps the most startling discovery was the number of worlds that may be contenders for a second Earth, at the right distance from their sun to have that ingredient so crucial for life as we know it, liquid water. Amongst them, we witness the most tantalizing discovery of all: a so-called ‘super-Earth’, situated in the Goldilocks zone - the area just the right distance from a sun to potentially support life - and with the faint signal of water in its atmosphere.

The incredible story of how Pluto has been propelled from an unremarkable ball of ice on the edge of the solar system to a world of unimaginable complexity - where some form of alien life might exist.
New discoveries from the edge of the solar system are transforming what is known about Pluto, thanks to the New Horizons space probe that took the first-ever close up images of the planet. Pluto was once thought to be geologically dead, but the pictures revealed it to be an active world of stunning complexity, with mountains carved from ice, a nitrogen glacier that appeared to be moving and a recently active volcano, with data sent back lead some scientists to speculate that there may even be life on Pluto today.

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.

Meet Perseverance, NASA's latest rover, as it heads to Mars to answer one question: did life exist on the red planet? On the way, it will lay the foundation for human exploration of our closest neighbour.
Today, Mars is hostile to life. It's too cold for water to stay liquid on the surface, and the thin atmosphere lets through high levels of radiation, potentially sterilizing the upper part of the soil. But it wasn't always like this. Some 3.5 billion years ago or more, water was flowing on the surface. It carved channels still visible today and pooled in impact craters. A thicker carbon dioxide atmosphere would have blocked more of the harmful radiation. The Mars 2020/Perseverance rover is designed to better understand the geology of Mars and seek signs of ancient life. The mission will collect and store a set of rock and soil samples that could be returned to Earth in the future. It will also test new technology to benefit future robotic and human exploration of Mars, as the Ingenuity Helicopter.

Our universe reveals itself in ways we’ve never seen before, thanks to new discoveries in astrobiology. Today, the advent of cutting-edge observational instruments is shedding light on amazing facts about life and the universe. NASA's next-generation space telescope TESS (Exoplanet Survey Satellite) has begun its search for Earth-like planets belonging to other star systems. How many of these 'exoplanets' can host life, and what kind of life forms can evolve in these environments?