Mercury’s surface discovery challenges conventional thinking

Scientists have discovered large scale buckling that created a giant valley on the surface of Mercury.

The researchers believe this shows proof of Mercury’s changing temperatures, contrary to the belief that Mercury has been steadily cooling since its formation. The valley discovered is about 250 miles wide and 600 miles long and is twice as deep as the Grand Canyon.

Dr Laurent Montesi, an assistant professor of geology at the University of Maryland and co-author of the study, said: “This is a huge valley. There is no evidence of any geological formation on Earth that matches this scale. Mercury experienced a very different type of deformation than anything we have seen on Earth. This is the first evidence of large-scale buckling of a planet."

Discovered using images from NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), the valley lies in the planet’s southern hemisphere, overlapping the Rembrandt Basin. The Basin is the result of an impact from an asteroid or something similar in size.

The valley’s walls appear to be two large, parallel fault scarps – step like structures where one side of a fault moved vertically alongside another. Because both scarps plunge steeply to the flat valley, Dr Montesi and his co-authors believe the interior of Mercury’s interior rapidly cooled forming a strong, thick lithosphere. The floor of the valley is a large part of the lithosphere that dropped between the faults on either side.

Dr Montesi said: “Most features on Mercury's surface are truly ancient, but there is evidence for recent volcanism and an active magnetic field. This evidence implies that the planet is warm inside. Everyone thought Mercury was a very cold planet--myself included. But it looks like Mercury might have heated significantly in recent planetary history.”

The valley was discovered by astronomers from the University of Maryland, the Smithsonian Institution, the German Institute of Planetary Research and Moscow State University. The research was published in Geophysical Research Letters.