Scientists Reveal Why Mercury's Surface Is So Dark

Posted: Mar 7 2016, 9:10pm CST | by , Updated: Mar 8 2016, 10:12pm CST, in News | Latest Science News


Scientists Reveal How Mercury Gets its Unusually Dark Surface
Credit: Courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Researchers have found abundant carbon on the surface of planet Mercury. The carbon originated from graphite rich crust.

Scientists have long been puzzled over the mysterious ‘darkness’ of planet Mercury. The surface of Mercury has a remarkably dark tint and scientists were previously unable to explain what makes it so dark. 

Now using data from the MESSENGER mission, researchers have found that there is a high abundance of carbon in Mercury’s surface and it came from the graphite rich crust deep below the surface. The impacts of comets caused the dragging of carbon to the surface. 

The new discovery rebuffs the assumption that carbon on Mercury’s surface was brought by comets, suggesting it is originated from the crust that is made of graphite. 

Researchers explain that planet Mercury was once very hot and hosted a global ocean of molten magma. Once magma cooled, solidified minerals submerged expect of graphite which was able to rise and float and eventually formed the crust of the Mercury. 

“The previous proposal of comets delivering carbon to Mercury was based on modeling and simulation,” said Larry Nittler, one of the investigators involved in MESSENGER mission. “Although we had prior suggestions that carbon may be the darkening agent, we had no direct evidence.”

“We used MESSENGER’s Neutron Spectrometer to spatially resolve the distribution of carbon and found that it is correlated with the darkest material on Mercury and this material most likely originated deep in the crust. Moreover, we used both neutrons and X-rays to confirm that the dark material is not enriched in iron, in contrast to the Moon where iron-rich minerals darkens the surface.”

NASA’s MESSENGER spacecraft orbited Mercury from 2011 to 2015 and made several close approaches to the planet during this period. When the spacecraft passed the concentrations of darkest material, they observed higher amounts of low-energy neutrons. It is an indication of high levels of carbon coming from surface and graphite is most likely the material that produced it. 

“The finding of abundant carbon on the surface suggests that we may be seeing remnants of Mercury’s original ancient crust mixed into the volcanic rocks and impact ejecta that form the surface we see today,” explained Nittler. “The result is a testament to the phenomenal success of the MESSENGER mission and adds to the long list of ways the innermost planet differs from its planetary neighbors and provides additional clues to the origin and early evolution of the inner Solar System.”

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Hira Bashir covers daily affairs around the world.




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