Researchers from Sun Yat-sen University in Zhuhai (SYSU) have discovered that the “dark planet” of the Solar System has a more complex surface than previously imagined.
According to South China Morning Post, scientists had formerly believed that Mercury—the smallest planet in the Solar System—had a dark surface due to being covered in graphite.
However, new analysis from the SYSU team indicates that the graphite content on Mercury’s surface is much lower than earlier estimates, with instead a presence of diamonds and various forms of amorphous carbon.
Mercury, the closest planet to the sun, may be full of diamonds – (Photo: NASA/SPACE TONIGHT).
Publishing their findings in the scientific journal Nature Astronomy, the researchers stated that they analyzed data from NASA’s MESSENGER spacecraft.
Previously, a team from Johns Hopkins University (USA) had led the hypothesis that the closest planet to the sun was covered in graphite, based on the mysterious low reflectivity of the planet’s surface.
The American team estimated that graphite made up as much as 4% of the uppermost sediment layer. The planet’s primordial crust was thought to contain even more graphite, but it had been buried under volcanic materials.
With the new analysis, the Chinese team claims that graphite constitutes only 1% of the planet’s surface material, as various other crystalline forms of carbon and metallic iron are sufficient to explain its unusual reflectivity.
“Crystalline graphite in the hypothesized primordial crust may have undergone metamorphosis or strong destruction due to surface processes, such as impacts from magma, meteorite collisions, and space weathering,” the research team from China explained.
According to SYSU authors, carbon on Mercury may primarily exist in the form of nano-phase diamonds due to prolonged metamorphic processes and as amorphous carbon due to space weathering.
Both of these materials are dark in color, rather than sparkling like the gemstones we typically see.
According to Professor Xiao Zhiyong from the School of Atmospheric Sciences at SYSU, the lead author, most of the graphite on Mercury has been altered after 4 billion years of weathering, which is why diamonds and amorphous carbon now dominate.
For more specific answers, scientists around the world are looking forward to the BepiColombo spacecraft from the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), which left Earth in 2018 and is expected to reach Mercury by the end of 2025.
