Ice-covered oceans and bleak craters: Where alien life might be hiding

If life exists elsewhere, it might not be on worlds like Earth. Here are some of the more peculiar places scientists are looking.

So far, the search for life beyond Earth has broadly focused on worlds like our own.

We have considered potentially habitable planets that might have land and water, are the right distance from their star to have temperatures similar to those found on Earth, and are around stars similar to the Sun. Life might even be found in the moons that orbit our near neighbours, like Mars or Jupiter.

But what if life exists in stranger locations than we expected?

Increasingly, scientists are exploring unusual places where alien life might exist, and sometimes looking for it in peculiar ways. From trapped oceans to spotting the patterns of star-hopping extraterrestrials, there is an increasing diversity of ideas.

"We have our eyes open and are thinking about different kinds of life signatures we could look for," says Lisa Kaltenegger, an astrobiologist at Cornell University in the US and author of the book Alien Earths. "We are pushing the possibilities to not miss signs of life."

All life on Earth has several common requirements. Every organism we know of needs liquid water and a source of energy – sunlight for plants, and food for animals. They are also all made of carbon: without it, simple or complex life on our planet wouldn't exist. But this might not all be true everywhere else.

One place already showing an unexpected potential for life is Venus. In 2020, astronomers announced hints of a gas called phosphine in its atmosphere. While this can be produced by processes such as volcanic eruptions (and its existence on Venus in any case remains contested), it can also be produced by life.

"We certainly did not expect" that Venus could have life, says Dave Clements, an astronomer at Imperial College London, although the idea was first touted back in the 1960s by the famous author and scientist Carl Sagan.

Venus seems an unusual place for life at first given that its surface can reach more than 400C (750F) and the pressure from the thick atmosphere is equivalent to standing at the bottom of Earth's oceans. About 55 to 65km (34 to 40 miles) above the surface of Venus, however, temperatures and pressures are the most Earth-like of any location in the solar system outside of our own world. It is here scientists think life could exist, as microbes floating in droplets among the clouds, burping out phosphine.

To find out more, several potential missions to Venus are planned. Clements is part of a UK-led mission called Verve (Venus Explorer for Reduced Vapours in the Environment), a small shoebox-sized spacecraft that Clements' team hopes will hitch a ride to Venus on an upcoming European mission called Envision, set to launch in 2031.

Once it arrived at Venus, Verve would detach and enter into a high, looping orbit around the planet, extending out to 200,000km (125,000 miles) but bringing it down to just 220km (135 miles) above the surface.

Here, Verve would probe the atmosphere of Venus for signs of phosphine, and life. It would have "a receiver specifically tuned to the wavelengths we are interested in", says Clements, phosphine being one but also ammonia and hydrogen. Taken together, these readings could give us hints that there is life floating in the atmosphere, or not.

 "This is not going to be a shaking-hands-with-little-green-men-type discovery of alien life," says Clements. "It's building the evidence for a case."

The Verve team is waiting to hear if they have been included on the Envision mission, a decision that will be made by the European Space Agency (Esa).

Another mission to Venus called Morning Star, from the US company Rocket Lab and the Massachusetts Institute of Technology, will launch a probe to Venus as soon as this year. It aims to dive into its atmosphere and look for a possible signature of life through a technique called fluorescence.

"Most people agree the frontrunners are Mars and Europa" to find life, says Clements. "But maybe the outside bet is Venus."

Elsewhere in the Solar System, the dwarf planet Ceres is another unexpected location now being probed for life.

Found in the asteroid belt between Mars and Jupiter, this world is small, four times smaller than our Moon, and has a greyish, lifeless appearance. But when it was orbited by Nasa's Dawn spacecraft from 2015 to 2018, scientists discovered something strange on its surface: bright spots that seemed to be some sort of salty, brine-like substance.

In August 2025, Sam Courville at Arizona State University in the US proposed that Ceres might have been habitable in its past, a surprising suggestion for a world that seems very dead to human eyes. He suggested the world could have had an ocean under its surface with a steady supply of heat, providing key requirements for life to emerge. And the bright spots today might be the remnants of that ocean seeping out from underground.

"Ceres has got a bunch of the basic ingredients for life," says Courville, including the right elements – carbon, sulphur, nitrogen, oxygen and phosphorous – and water. "But you also need energy. You need something for life to use to power itself."

Courville's work showed that Ceres might have had this source of energy about 2.5 billion years ago due to chemical reactions in the world's interior, specifically the decay of long-lived radioactive isotopes such as potassium-40, which can take more than a billion years to break down.

"That's what can keep Ceres warm and even cause it to heat up to 500C (930F) in its interior," says Courville. That’s hot enough to be "chemically significant" to provide energy for life, he says.

To know for certain we would need to send a spacecraft to Ceres to scoop material from its surface – maybe from one of its bright spots – and bring it back to Earth to study. "Then you can do all sorts of crazy analysis on the sample," says Courville. Nasa has previously considered such a mission.

Farther out in the Solar System, trapped oceans (those hidden under a thick layer of ice) are increasingly in vogue. Two spacecraft – Nasa's Europa Clipper and Esa's Jupiter Icy Moons Explorer (Juice) – are currently on their way to Jupiter to probe heavily suspected oceans under the moons Europa and Ganymede respectively.

Europa, in particular, looks promising as a place to search for life, with its ocean thought to be in contact with a rocky sea floor, providing an environment more likely to have nutrients for microbes.

Occasionally what is thought to be a liquid ocean spurts out onto the frozen surface of Europa, which Europa Clipper will try to investigate from afar. In the future, scientists dream of sending a lander to Europa that includes a melt probe, a device that would burrow through kilometres of ice to directly access the ocean and look for life.

Europa, and equally Saturn's moon Enceladus, are high on target lists to hunt for life. But increasingly scientists are discovering that oceans might exist inside many other worlds too by re-analysing data from spacecraft and telescopes.

"Our thinking has changed about icy ocean worlds," says Alyssa Rhoden, a planetary scientist at the Southwest Research Institute in the US, greatly expanding the potential locations for habitability in the Solar System.

Saturn's moon Mimas, Neptune's moon Triton, and even Pluto all look like good candidates for having had liquid water oceans under their surfaces at some point in time, and with them the potential for habitable environments to exist. That could mean a much wider array of worlds might have oceans including those far from the Sun, like Pluto, or very small, like Mimas.

Outside of our Solar System, one of the key ways to look for life is by probing the atmospheres of worlds around other stars, called exoplanets. Astronomers are already starting to do this with telescopes like the James Webb Space Telescope (JWST), but the process is in its infancy. Systems like Trappist-1, which contains seven Earth-sized worlds orbiting a red dwarf star, much smaller than our Sun, are especially promising.

One left-field way to search for life on exoplanets might be to look for signs of planet-hopping civilisations, according to Harrison Smith, an astronomer at the Institute of Science Tokyo in Japan.

If advanced alien life exists somewhere in the galaxy, we might expect that at some point it could have depleted the resources of its home world – if it had been around much longer than humanity, for example – and moved on to other planets. Looking for patterns in the atmospheres of planets, we might therefore be able to spot signs of a civilisation jumping from place to place.

"There might be a new way you could look for life by identifying a particular arrangement of atmospheres," says Smith. "If we imagine such a thing happening at a large scale, we could be able to observe that in the patterns of these atmospheric observations."

The idea is that an alien civilisation might terraform any planet it moved to, changing the conditions of the planet to make it more like their home world. If multiple planets in the vicinity of each other around the same or different stars have similar atmospheric compositions, it could be a sign of this.

"If you were going between planets, you would want to make your atmosphere comfortable," says Smith. "And that would show up regardless of the technology you use to change the atmosphere."

One way to test the idea is with an upcoming Esa telescope called Ariel. Launching in 2031, it will study the atmospheres of 1,000 exoplanets, enabling astronomers like Smith to hunt for life. "Ariel will open the door for a lot of new approaches," he says.

Another peculiar place we might hunt for alien life is around pulsars, city-sized remnants of exploded stars that can rotate thousands of times per minute. Some are known as spider pulsars, where a companion star is being ripped apart by the pulsar.

Despite seeming to be hostile to life, they could actually be a way for an advanced civilisation to move across the galaxy says Clément Vidal, a philosopher at Vrije Universiteit Brussel in Belgium.

In these systems the pulsar would evaporate material from its companion, producing thrust. If an advanced civilisation could surround the star in machines, such as a Dyson sphere, they might be able to direct the thrust, giving them an engine to explore the galaxy.

Already Vidal has seen one spider pulsar system he thinks might be worth following up, because it will pass close to another star in 420 years. "On a stellar dynamics time scale this is very short and very unlikely, because space is mostly empty," he says, suggesting it might be a Dyson sphere steering in the star's direction.

Other searches for advanced alien life, such as looking for radio signals through projects like Breakthrough Listen, have come up empty handed so far in hunts for bright radio beacons from the nearest stars to our Sun. So astronomers are now beginning to explore more unorthodox ideas, says Jason Wright, an astronomer at Pennsylvania State University in the US, such as "giant computers surrounding the black hole at the centre of the Milky Way" – a very unexpected place to find life, but one that could offer a vast source of energy.

More like this:

• What alien languages might sound like

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• Why aliens may be weirder than we think

Another possibility might be closer to home. Occasionally, objects from other stars pass through our Solar System. Three such interstellar objects have been spotted before, all of which were identified as asteroids and comets. But it might be possible that one of these objects in future is an alien spaceship, says Wright, sent to take a look at our planets.

If so, we might see telltale signatures of technology using telescopes like the Vera C Rubin Observatory in Chile, which became fully operational this summer. "Perhaps it would have some thrust," says Wright, changing its orbit as it moved past the Sun. "Rubin, for the first time, will be able to find such things."

As unlikely as it seems, maybe a passing spaceship truly will be our first sign of alien life. Or perhaps it will be traces of a gas on a seemingly lifeless world, biology-rich plumes spouting from a frozen ocean, or signs of a rapidly spinning star suddenly changing course. If there is life out there, there is no shortage of ideas on how to find it.

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