The planet Mercury has a surface composed of graphite carbon, a substance that usually takes the form of pencil lead here on Earth, scientists have discovered.
"If we've really identified the remains of Mercury's original crust, then understanding its properties provides a means for understanding Mercury's earliest history," Patrick Peplowski of the Johns Hopkins University Applied Physics Laboratory (APL) explained this week,
the BBC reported.
Peplowski and his colleagues made their discovery using data from NASA's Mercury Messenger spacecraft, which was launched in 2004 and has circled Venus as well. They
published their findings Monday in the journal Nature Geoscience.
The researchers said in their entry that the prevailing hypothesis about the carbon on Mercury is that it was deposited there by comets.
Instead, the data suggests that Mercury likely had a molten magma ocean when it was very young. The graphite part of the magma remained the most buoyant substance as the planet's surface cooled into a crust.
That graphite crust was obscured somewhat over the millennia, however, by volcanic activity and impacts,
The Daily Mail explained.
Each time the surface was hit by a space rock, however, some graphite was disturbed, and distributed back toward the surface.
This cycle resulted in Mercury having one of the darkest aspects of any object in the solar system. It reflects only 12 percent of the sunlight that falls on it, and now we know why.
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