For many years, our planet has been thought of as a planet of distinction. Aside from being the only planet in our solar system that is able to host life (at least, that we know of), it is also thought of as the only one that still has active tectonic activity. This means that its plates still move and form faults, resulting in various phenomena such as earthquakes, volcano formation, and mountain building.
Tectonic activity arises from heat. Billions of years ago, just after formation, the terrestrial planets were very hot. Over time, they have cooled. In the Earth's case, this cooling takes place through convection, where hot materials slowly rise to the surface and release heat. Being a rocky planet, rocks subjected to intense pressure and heat flow slowly—these are called convection currents. These currents are what cause the rigid plates in our planet's surface to move.
A (literally) Groundbreaking Discovery
In an paper published in Nature Geoscience, scientists report that images from by NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft show previously undetected cliff-like landforms on Mercury's surface. These scarps, which resemble stair steps, have given scientists reason to believe that Mercury is still tectonically active. Since such small deformations could not have possibly survived the steady bombardment of space debris, they are thought to be very young.
During the past 18 months, the MESSENGER spacecraft was gradually lowered, allowing it to take higher resolution images of the planet, revealing the previously undetected scarps. These ridges also imply that Mercury's outer core is still hot, and the planet is still contracting.
“This is why we explore,” said NASA Planetary Science Director Jim Green at Headquarters in Washington, D.C. “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.”
This discovery underscores the importance of exploration. Though the fact still remains that Mercury is uninhabitable, the findings still contribute towards our understanding other celestial bodies in the solar system.