When we think about searching for alien life, most people imagine Earth-like planets orbiting distant stars, bathed in the warmth of their suns and perhaps hosting oceans of liquid water. But what if we’ve been looking in the wrong places all along?
A growing number of scientists, including world-famous astrophysicist professor Avi Loevb believe that we should be expanding our search—not for life, but for technosignatures, the telltale signs of advanced technology. As Professor Loeb explains, some of the best candidates might be frozen worlds, far from the traditional habitable zone.
We typically assume life must exist in a “Goldilocks zone”—not too hot, not too cold—where water can remain in a liquid state. But nature rarely sticks to our expectations. Saturn’s moon Titan, for example, is frigid, with surface temperatures hovering around 90 Kelvin (roughly -180°C). Yet NASA’s upcoming Dragonfly mission, launching in 2028, will explore this icy moon for signs of life in its methane lakes.
Even colder worlds—icy moons and rogue planets drifting without a star—might host liquid water oceans beneath their frozen crusts. But here’s the twist: if intelligent life ever arose in such hidden oceans, it might never look up to see the stars. As Loeb puts it, without a sky, would they ever dream of building rockets?
Technological life doesn’t need comfort
While biological beings like us need warmth, water, and protection, artificial life doesn’t. Robots and probes don’t care about temperature, atmosphere, or even sunlight. This is exactly why some scientists suggest that the best places to look for advanced civilizations may not be hospitable planets—but the uninhabitable ones.
Loeb says we should think about it: a civilization far older than ours might have sent autonomous machines across the galaxy. These machines could land on any solid surface, including icy rogue planets or barren moons, and start building. They wouldn’t need a breathable atmosphere or a warm climate. All they’d need is raw material.
And because light takes tens of thousands of years to travel across the galaxy, these probes would need to operate independently—like scouts establishing a technological foothold for civilizations that may no longer even exist.
Where should we look?
Here are some prime targets in the search for technosignatures:
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Rogue planets: These are planets that drift through space without orbiting a star. They’ve been found using gravitational microlensing and may actually outnumber stars in our galaxy.
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Icy moons: Moons like Europa, Enceladus, and Titan may have subsurface oceans and mineral-rich surfaces—ideal for machines to operate or harvest resources.
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Airless rocky planets: Planets like those in the TRAPPIST-1 system, with multiple rocky worlds packed into a small space, could offer plenty of landing spots for robotic explorers.
Technosignatures could be anything from artificial radio bursts to unusual surface structures, energy emissions, or even planetary surfaces altered by mining or construction. Think of them as cosmic archaeological sites—clues left behind by visitors from long ago.
And if we find such a clue? We might not understand who sent it, or why, but like detectives at a crime scene, we could begin piecing together a story from what was left behind.
What if the senders are long gone?
It’s possible that we’re looking not for neighbors—but for ghosts of civilizations past. We might uncover robotic artifacts or technological ruins on dead planets, long after their creators vanished.
But even then, the discovery would change everything. It would tell us that we’re not alone, that someone else reached the stars before us, and perhaps offer a glimpse of what lies ahead in our own future.
In the words of astrophysicist Avi Loeb, exploring these possible robotic visitors might feel like stepping out of Plato’s cave—trying to understand the world beyond by studying only the shadows it leaves behind. If we ever do stumble upon a relic, it may not just reveal an ancient traveler—it may inspire us to become one.
