Images from Nasa's Messenger spacecraft have revealed Mercury is a tectonically active planet and is still contracting - raising the possibility of earthquakes.
It was previously thought that the only planet in the solar system to still be tectonically active, and thus suffer earthquakes, was Earth. All the other planets were thought to be too old.
But now small fault scarps, or cliff-like banks, have been spotted on the surface of Mercury. A team of researchers at the National Air and Space Museum believe they are young in geological terms.
The scarps have tens of metres of relief and are just kilometres in length, comparable in scale to scarps on the moon, and it is believed that they are less than 50 million years old.
The new findings, published in the journal Nature Geoscience, are consistent with another recent finding, which claimed Mercury's magnetic field has existed for billions of years, and the hot outer core is still cooling.
It is hoped that Mercury's susceptibility to earthquakes can one day be proved by seismometers.