The search for life in space

From missions exploring the ancient lakes of Mars to the discovery of planets outside our solar system, we’re continuously trying to answer the question – are we alone?

Our fascination with extraterrestrial life

Throughout history, we’ve looked up to the night sky and been drawn to the unknowns of what lies beyond.

Dr Helena Bates, our Postdoctoral Researcher says, “I think we’ve always been fascinated by the sky and space and our position in space. When we started learning more about it, we realised that life out there wasn’t immediately obvious. People wanted there to be life elsewhere because the idea of us being alone is quite scary.”

The discovery of life in space might also provide us with information about where we came from, which could help us to learn more about our own planet.

“I think we’re hoping that by looking for life that’s possibly at a different stage of its evolution we could have a better understanding of how life came to be on Earth, which is one of the greatest unknowns we have,” Helena explains.

Where are we looking for life?

We know that the conditions on Earth can support life, and one of the most important parts of survival on our planet is water. When thinking about the conditions to support life in space, scientists use the phrase goldilocks zone or habitable zone to describe an area around a star that’s not too hot or too cold for liquid water.

Due to our understanding of life on Earth, when searching for life in space, the main areas of focus are places that might have, or once have had, similar conditions to ours.

Within our solar system, our nearest neighbour Mars is most frequently studied for signs of life. The red planet is about half the size of Earth and has an extremely thin atmosphere that mainly consists of carbon dioxide.

Although the conditions of present-day Mars would probably not support life as we know it, scientists are instead looking for evidence of previous life.

We know that Mars was once probably much wetter and warmer. Evidence of riverbeds and dried-up lakes indicate that Mars almost certainly once had water.

Helena remarks “Mars is not very habitable now, but it was. There’s a chance that at some point in Mars’s geological history, it did have an environment very similar to Earth, which could suggest it once hosted life.”

Due to our knowledge of Mars’s past, there have been many missions to look for signs of life there. In 2021, the Perseverance rover landed and began its search for potential signs of ancient microbial life. It landed in Mars’s Jezero Crater – an area that scientists believe was once home to a lake and a river billions of years ago. Scientists theorise that we might find evidence of microbes that once lived in the lake.

Another place in our solar system that we’re exploring for signs of life are the moons of the planet Jupiter. The Jupiter Icy Moons Explorer, also known as Juice, is an uncrewed spacecraft. It was launched in 2023 to explore Europa, Ganymede and Callisto – three of Jupiter’s moons.

Jupiter is a gas giant – a large planet mostly composed of helium and hydrogen that has swirling gases above a solid core rather than a hard surface. It has 95 known moons and even though these lie far beyond the goldilocks zone, scientists still believe that the possibility of life should be explored there. Experts think the three moons that Juice is exploring could have liquid oceans underneath their icy surfaces.

Scientists believe that the oceans of Ganymede and Callisto are sandwiched between layers of ice. Their icy outer shells could be around 160 kilometres thick while another layer of ice on their seafloors prevents chemical nutrients from entering the oceans.

Europa’s icy shell, however, is only about 24 kilometres thick, and it has no layer of ice on its seafloor. While Earth gets its energy from the Sun – the ocean of Europa could be getting energy from the warm rocks of the seafloor. We know from Earth that like water, energy is a key ingredient for life.

We’re also looking for life outside our solar system on exoplanets. One of these planets is called K2-18 b and it falls within the goldilocks zone. This planet is nearly nine times the mass of Earth and about 124 light-years away. In 2019, the Hubble Telescope detected water vapour in K2-18 b’s atmosphere and later the James Webb Telescope detected carbon dioxide.

There have also been traces of two chemicals that are associated with life found in K2-18 b’s atmosphere – dimethyl sulphide and dimethyl disulphide. On Earth, these gases are produced by marine plankton and bacteria.

Making contact

Our galaxy is estimated to contain anywhere from 100 billion to 400 billion stars and planets. There could be at least 60 billion planets in the habitable zone. But if this is the case, why haven’t we found life? This question has coined its own term – the Fermi paradox.

Missions to find life are currently mainly focused on microbes or signs of previous life forms. To do this, we look for biosignatures – elements, molecules or substances that might indicate life. However, some scientists suggest that we could find ‘intelligent life’ by locating technosignatures – evidence of the use of technology.

Intercepting radio signals from a distant exoplanet or picking up laser signals or abnormalities in light could all point to activity from intelligent life.

What’s needed for life to survive and thrive?

Life can take many forms and can thrive in a huge variety of habitats. By understanding how humans, animals, plants and microbes survive on Earth, scientists can form a clearer idea of what life might need to survive and thrive in space.

“We find carbon-bearing molecules – the stuff that builds life on Earth – all over the solar system. Based on this, I think it’s most likely that if we were to find life in our solar system, it would be carbon based,” says Helena.

If the life found in our solar system was carbon based, it would need conditions similar to our own to survive and thrive – stable temperatures, a source of energy, liquid water and time.

“We have a relatively temperate climate, relatively stable geology and lots of liquid water. We’re close enough to the Sun where it’s not too hot and not too cold,” says Helena.

However, we only understand life as we know it, and there could be many more life forms, all requiring different conditions.

Helena explains “not all life on Earth can survive in all Earth environments – a fish would not thrive on land for example. There are many factors that need to be considered in the search for life.”

The search for life continues

With telescopes looking into the depths of space and robots searching for minute signs of life on our neighbouring planets, we’re determined to find out if we’re alone in the universe.

Explore this big question at our new exhibition, Space: Could Life Exist Beyond Earth? Open 16 May 2025 to 22 February 2026. Book your tickets.