LHS 3844b: Scientists find a bizarre 'tidally locked' planet that could host life, but it never has a day or night

A planet where one half is scorched at temperatures up to 2,000 Kelvin and the other half is colder than any spot on Earth might still have a shot at hosting life, according to a new study led by researchers at the University of Pennsylvania. The planet in question, LHS 3844b, sits 48.5 light years away and never rotates the way Earth does, it always shows the same face to its star, leaving one side in eternal daylight and the other in permanent, bone-chilling darkness.

That kind of extreme split-personality climate would normally be written off as a dead end for biology. But the new research, published in Nature Communications, suggests the planet's own geology may be quietly working in life's favour by moving heat around under the surface.

Why "Permanent Day, Permanent Night" Is More Common Than You'd Think

Planets like LHS 3844b are called "tidally locked", their spin and their orbit move at exactly the same pace, so they never turn to show a different face to their star, much like how the Moon always shows the same side to Earth. Far from being some cosmic oddity, researchers say worlds like this actually outnumber Earth-like planets with a normal day-night cycle, especially among planets and moons that sit close to their parent star.


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Daisuke Noto, a postdoctoral researcher at Penn's GEFLOW Lab and one of the study's authors, said tidal locking is a routine outcome for bodies orbiting tight and fast, not a rare glitch. On paper, the temperature gap this creates looks brutal enough to rule out life entirely. But Noto isn't ready to write these planets off. As he put it: "life might find a way."

Building an Alien Planet on a Tabletop

Instead of running the study purely on computers, the team decided to recreate the guts of a tidally locked planet in a lab tank. Noto joked that building a real exoplanet was never going to fit the budget, so the team improvised with a rectangular tank filled with thick glycerol fluid and colour-changing liquid crystals that shift shade as temperatures move up or down.

Four separate thermostats were fitted around the tank to heat and cool different zones, mimicking the blazing dayside, the frozen nightside, the surface, and the deep interior all at once, essentially building a miniature, working model of the planet's mantle, the thick rocky layer sandwiched between crust and core.

A Slow, Steady Planetary Heartbeat

The tank experiment threw up a strikingly orderly pattern. Heated material rose on the "day" end, drifted across the top, cooled as it neared the "night" end, then sank and looped back underneath, a single, unbroken circulation loop running again and again like clockwork. Occasional mushroom-shaped plumes also rose from the tank's heated base, but unlike Earth's shifting volcanic hotspots such as Hawaii or Iceland, these stayed rooted to the same spot instead of drifting.

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Crucially, the heat-transport readings from the tank, a measure scientists call the Nusselt number, came out comparable to figures seen in Earth's own mantle. That match hints that some tidally locked worlds could sustain localised warm zones underground, potentially livable pockets tucked into the planet's mid-latitudes even while the surface swings between fire and ice.

Scientists already doing follow-up experiments

The team believes this steady internal circulation could also stir the planet's molten core, possibly generating a magnetic field quite unlike Earth's, a shield that matters because magnetic fields help protect atmospheres from being stripped away by stellar radiation. That part hasn't been tested yet, but the researchers are already planning follow-up lab experiments to dig into it, alongside broader work on how heat and fluids move through confined natural systems on Earth.

For now, the takeaway is simple: a planet baking on one side and freezing on the other doesn't have to be a lifeless one. Somewhere in that slow underground churn, there might just be room for something to survive.

(Source: University of Pennsylvania / study published in Nature Communications, based on research by Daisuke Noto, Hugo Ulloa, and collaborators from the Japan Agency for Marine-Earth Science and Technology and Hokkaido University)