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.
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An enhanced-color image of Mercury, showing the
carbon-rich material related with impact craters. Image Credit:
NASA/JHUAPL/Carnegie Institution of Washington
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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.”
