Mercury's peculiar surface a mystery no more; NASA scientists solve the puzzle!

New Delhi: Mercury has been one of the most mysterious planets of our solar system and since its the planet closest to the sun, its structure and evolution has intrigued scientists the most.

One of the most longstanding mysteries of the planet was that a part of Mercury's surface looks new and the other part appears to be old. But thanks to NASA's team scientists at Johnson Space Center, the mystery has been solved.

Working with data from NASA’s MESSENGER spacecraft, which orbited Mercury from 2011 to 2015, scientists in the Astromaterials Research and Exploration Science Division have found that Mercury is extremely diverse.

As per NASA, One area of the planet, the Northern Volcanic Plains, is very young while the other is older and consists of intercrater plains and heavily cratered terrains. Until now, there has been no good explanation for how such heterogenerous compositions could develop.

“We think that planets start hot and almost completely melt,” said Dr. Asmaa Boujibar, NASA postdoctoral fellow and lead author of the study. “As they cool, they crystallize various minerals. In some cases, minerals can separate to form different layers inside the planets.”

Earth’s Moon is a good example of this as shown in samples brought back during the Apollo missions. In contrast, Earth does not seem to have these layers, either because the minerals never separated, or because the movement of its surface plates, called tectonics, has mixed everything up again, Boujibar said. So the research team at Johnson set out to answer the big question about Mercury, which is whether its interior would be chemically layered like the Moon, or homogenous like the Earth. Previous studies suggested that the surface of Mercury is so heterogeneous that the mantle had to be compositionally layered like the Moon.

In particular, the study shows that older terrains on Mercury have formed by material melting deep in the boundary between the core and mantle, while younger terrains formed closer to the surface. At reduced conditions, sulfur dissolves into the silicate mantle and also influences the melting and melt compositions. The combined effects of pressure and sulfur explain the overall heterogeneous surface composition of Mercury, NASA reported.