Astronomers say Mercury is geologically active like Earth. It was previously thought that our blue planet was the only tectonically active planet in our Solar System, but NASA has now proved that Mercury also fits this description.
Mercury is the smallest planet in the Solar System with an orbital period of about 88 Earth days. During the day, temperatures on Mercury’s surface can reach 800 degrees Fahrenheit (430 degrees Celsius) because it has no atmosphere to retain that heat. Temperatures on the surface can drop to -280 degrees Fahrenheit (-170 degrees Celsius) at night.
This week, a team of scientists composed of Thomas R. Watters, Katie Daud, Maria E. Banks, Michelle M. Selvans, and Clark R. Chapman published a study in Nature Geoscience, which showed that Mercury exhibits seismic activity.
By analyzing images from NASA’s Mercury Surface Space Environment Geochemistry and Ranging Spacecraft or MESSENGER, the experts spotted fault scarps that have not been impacted by asteroids. A fault scarp is “a small step or offset on the ground surface where one side of a fault has moved vertically on the other.”
The fault scarps are located on the little inhospitable planet’s north pole, and the images were taken in the final months of the MESSENGER mission.
MESSENGER orbited Mercury between 2011 and 2015 and crashed into the planet’s surface on April 30, 2015, and now the scientists are studying the images collected by the robotic spacecraft. According to the scientists, the cliffs are about 50 million years old, much younger than the other features on Mercury’s landscape that are billions of years in age.
However, do not expect these new fault scarps to be around for long because meteorites are constantly bombarding Mercury’s surface. Lead author Tom Watters, Smithsonian senior scientist at the National Air and Space Museum in Washington, D.C., said:
“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.”
The first spacecraft to visit Mercury was NASA’s Mariner 10 (1974–1975), and it captured pictures of ancient scarps and craters, which seemed to indicate that the planet while formerly geologically active, had been dead for millions of years. NASA Planetary Science Director Jim Green stated:
“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.”
According to Watters, the small scarps also mean that Mercury’s surface is still fracturing as it slowly contracts and cools. Sean Solomon, a planetary scientist at Columbia University, explained that the planet is shrinking as it slowly cools.
The lack of atmosphere on the planet makes it possible to see the scarps left behind by the shrinking process. Earth’s moon has also been shrinking for the same reason. Watters explained:
“Mercury has the potential for many more earthquakes than the moon since it’s contracted a lot more than the moon has.”
Apollo astronauts set seismometers on the moon that recorded 28 moonquakes ranging from magnitude 1.5 to 5 on the Richter scale between 1969 and 1977. Watters added:
“The biggest of these features is comparable to the San Andreas [fault]. They’re huge. So we know Mercury had contracted, but we didn’t know if that contraction had happened millions or billions of years ago, because large features with kilometers of relief will not disappear.”
Experts believe that Venus is another geologically active planet, but it is hard to confirm this theory because the thick clouds around it make it difficult to study the geological processes.