Earth was first believed to be the only tectonically active planet in the Solar System, but a recent discovery added another one in the roster. As NASA's MESSENGER observed, Mercury has active geological activities as well.

Mercury is less likely to host human life when compared to Mars. But it also has its own Earth-like properties, like the tectonic activities underground. Scientists confirmed this after signs of fault lines were discovered on the surface of Mercury.

NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) detected small scraps that are believed to be "geologically young", which means that these scarps were caused by recent activities. "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," lead author Tom Watters, Smithsonian senior scientist at the National Air and Space Museum said in a press release.

This new finding makes Earth and Mercury the only two tectonically active planets within the Solar System. However, experts are quick to remind the public that this doesn't mean Mercury has also increased its ranking when it comes to human habitability.

MESSENGER spent 18 months in orbit close to Mercury's surface to gather data about the planet. Its successful mission captured never-before-seen images of scarps, landforms that look like steps that lead researchers to conclude that these scarps are still very young.

But it doesn't stop there; researchers believe that the planet is still active until today, just like Earth. It may not be as active as Earth but at least there are and there will be movement undergrounds that may cause future disturbance and geologically determined scarps appearing on its surface every now and then.

Mercury's 88-day Earth orbit around the Sun still makes it less likely to be uninhabitable. There's also no atmosphere and with unforgiving temperature ranging from -173 degrees Celsius at night to 427 degrees Celsius by day, according to a report.

Although this finding did not add another potential planet for habitation, NASA is still pleased with MESSENGER's finding since it will enable scientists to better understand the Solar System and the universe.

"This is why we explore," Jim Green, NASA's planetary science director said in a statement. "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," Green added.