There’s something about the planet Mercury that just doesn’t make proper sense to astronomers: It’s too dark. Even darker than the Moon, despite having way less iron. But at long last, researchers have finally cracked the mystery—and their discovery is providing a better insight about the interesting past of the Solar System’s innermost planet. Mercury is slathered in graphite; the same slate-colored, carbon-based material we put in our pencils.
An enhanced-color image of Mercury, showing the carbon-rich material related with impact craters. Image Credit: NASA/JHUAPL/Carnegie Institution of Washington
The bits of graphite on Mercury’s surface nowadays may be the uncovered leftovers of a thick carbon crust that made from an ancient lava ocean, according to a new study issued yesterday in Nature Geoscience. Patrick Peplowski, lead author on the new study, told Gizmodo “This was really a huge surprise. The question is: if there’s several percent carbon on Mercury’s surface and not on the other planets, what process could have concentrated it?”
The graphite data, gathered during low-altitude flyovers in the last days of MESSENGER’s mission, shows that Mercury’s surface could be made up of a few percent carbon, way more than other rocky planets in our Solar System. And the carbon was not delivered-via-comets instead MESSENGER’s data is consistent with local carbon that created deep within the planet.
When Mercury was young and even way hotter than it is at the moment, its surface was a blending mess of magma. Graphite, as the authors say, could have crystallized out of that magma ocean, creating a primordial crust, the leftovers of which sit underneath the planet’s surface today and are now being uncovered during extraterrestrial impacts.
Peplowski said “We’re still refining our understanding of how the Earth-Moon system formed after numerous missions. To think we really understand the early history of Mercury is naive.”
He continued “MESSENGER returned a huge data set and we’ve only looked at a fraction of it,” “I think we’ll find there’s rich data to be mined for years to come.”