For decades, Earth was thought to be the only planet in our Solar System with active tectonics—a trait linked to its ability to sustain life.
But recent discoveries have turned this assumption on its head.
NASA’s MESSENGER spacecraft has provided compelling evidence that Mercury, the smallest planet in our Solar System, is still geologically active.
This revelation came from high-resolution images taken during MESSENGER’s final 18 months in orbit.
The spacecraft captured previously undetected fault scarps—step-like cliffs that form when a planet’s crust contracts.
What makes these features remarkable is their size and apparent youth, suggesting that Mercury’s interior is still cooling, causing its crust to shift and crack in real time.
Challenging Long-Held Assumptions
For years, scientists believed Mercury’s tectonic activity had long ceased.
But these fault scarps, small and relatively unweathered, indicate that the planet continues to contract—a process that mirrors Earth’s tectonic behavior, albeit on a smaller scale.
“The young age of the small scarps means that Mercury joins Earth as a tectonically active planet, with new faults likely forming today as Mercury’s interior continues to cool and the planet contracts,” explains Tom Watters, a Smithsonian senior scientist at the National Air and Space Museum in Washington, DC.
This discovery alters our fundamental understanding of Mercury’s evolution.
Rather than being a geologically dead world, it appears to be a dynamic, changing planet—one that may still experience planetary quakes, much like Earth.
A Harsh, Unforgiving World
While Mercury might share tectonic activity with Earth, its extreme environment remains inhospitable to life.
The planet orbits the Sun in just 88 Earth days, has virtually no atmosphere, and experiences drastic temperature swings—from a bone-chilling -173°C (-280°F) at night to a scorching 427°C (800°F) during the day.
Even with its tectonic activity, Mercury is unlikely to support life.
But the discovery of its geological dynamism has broader implications: if tectonics can persist on Mercury, where else might we find them?
The Case for Europa
While Mercury’s tectonic activity is now confirmed, another celestial body may also be geologically active: Europa, one of Jupiter’s moons.
Scientists have long suspected that Europa’s surface undergoes continuous transformation, possibly driven by tidal forces from Jupiter’s gravity.
Unlike Mercury, Europa is a prime candidate for extraterrestrial life.
Beneath its icy crust lies a vast subsurface ocean, potentially warmed by geothermal activity.
This ocean—kept liquid by the moon’s tectonic movements—could harbor life forms, making Europa one of the most intriguing objects in the search for life beyond Earth.
Why This Discovery Matters
Beyond rewriting textbooks on Mercury, this finding forces us to rethink planetary evolution as a whole.
Could tectonic activity be more common across planets and moons than we previously thought?
If Mercury—a planet so small it was assumed to have cooled and solidified eons ago—is still shifting and cracking, it suggests that other planetary bodies could also be experiencing similar processes.
“This is why we explore,” says Jim Green, NASA’s planetary science director.
“For years, scientists believed that Mercury’s tectonic activity was in the distant past.
It’s exciting to consider that this small planet—not much larger than Earth’s Moon—is active even today.”
What’s Next?
Researchers will continue analyzing Mercury’s magnetic field and surface geology to uncover more about its tectonic activity.
There is also mounting evidence that Mercury experiences quakes—a phenomenon that, if confirmed, would further solidify its status as a dynamic world.
But the biggest takeaway is this: we’ve only begun to scratch the surface of what’s happening on planets beyond Earth.
With new missions on the horizon, from exploring Europa’s icy waters to investigating Mars’ seismic activity, the search for active geology—and, perhaps, the conditions for life—continues.
