Where we might find aliens in the next decade

Forget UFOs and alien abductions, here’s how scientists are really looking for life on other worlds.
It is easy to wax lyrical about aliens. The prospect of life on other planets has shaped much of our culture and continues to inspire books, TV shows, movies – and the odd conspiracy theory of course. But amongst all the fantastical visions of little green men there is a real, actual hunt for alien life taking place right now, and it is not some fringe science or controversial idea. It is a systematic process that scientists are undertaking, with results expected in as little as a decade.
To be more exact, there are multiple hunts for alien life currently underway. On Mars, a rover is collecting samples that may determine if life ever existed on the red planet. Probes are visiting some of our solar system’s icy moons to search for signs of habitability. Astronomers are also beginning to scour the atmospheres of planets beyond our own solar system for telltale elemental cocktails that hint at alien life. And, yes, we are even keeping a beady eye out for signals from any intelligent civilisation that might purposefully – or accidentally – make contact.
“I think in 10 years we’ll have some evidence about whether there’s anything organic on some nearby planets,” says Lord Martin Rees, the UK astronomer royal. “I think we are really [on the cusp].”
Alien life, if it exists, has not made itself easily known. Early attempts to search for extraterrestrial intelligence, called Seti, began in the mid-20th Century, with astronomers looking in vain for radio signals on other planets. Mars, which was believed in the late 19th Century to have life-harbouring canals and rivers, was discovered to be a mostly dry, barren wasteland. Planets around other stars, meanwhile, were so small that finding them was difficult, let alone learning much about them.
To hunt for alien life we have had to fine-tune how we search for it, and prepare for the possibility that any initial detection is likely to be perhaps somewhat small – evidence of microbes or chemical markers in a distant atmosphere. Compared to the Hollywood vision of first contacts with extra-terrestrial life, it might seem anticlimactic, but hard evidence that life exists beyond the boundaries of our own planet will still fundamentally alter our view of our place in the Universe.
In our solar system, Mars is arguably the most popular destination to hunt for life, at present. We know the planet was likely wet and potentially habitable billions of years ago, with seas and lakes on its surface. More recently scientists have even found tantalizing clues that there may be liquid water on Mars still, hidden beneath the planet’s southern ice cap.
Nasa’s Perseverance rover has been scooping up samples from a dried-up lake in a region called Jezero Crater, just to the north of the Martian equator. The goal is to collect dozens of samples and return these to Earth in the early 2030s – a mission known as Mars Sample Return – where they can be investigated in detail for signs of life. The mission is currently facing difficulties, with the return aspect struggling for funding, particularly due to cuts to the US space budget under President Donald Trump. But if they do manage to pull it off, there are scientific riches in store.
Susanne Schwenzer, a planetary scientist at The Open University in the UK and a member of the Mars Sample Return science team, says the presence of past life on Mars could leave a fingerprint in the interaction of its rocks and water. “If you have life, things look very different,” she says. “If we have the samples from Mars, we can go into miniature detail to study these processes.” It’s possible some of the samples could even contain fossilised microbes inside the rocks. “I as a scientist wouldn’t have spent my life on this if I weren’t hopeful that we have a good chance of finding something,” says Schwenzer. “I hope we wil, but I can’t predict it.” But even if signs of life on Mars were to be detected, it would not be unequivocal proof of widespread alien life elsewhere in the universe. Mars and Earth are known to have shared material early in their history, meaning they might also have shared the genesis of life. For evidence of a true second genesis, proof that life arose for a second time independently on another world, scientists are looking to the solar system’s icy moons such as Jupiter’s Europa and Saturn’s Enceladus, thought to contain vast oceans beneath their frozen surfaces. “If we were to find life on the icy moons, we would be sure this is a different genesis of life from Earth,” says Schwenzer. (Read more about what life in alien oceans might be like. (BBC)