A new study says that the dark surface of Mercury is because of passing comets which produces dusting of carbon. The surface of Mercury is low in iron that is one of the reasons why the planet does not reflect light efficiently.
Researchers first made a model on how much carbon rich material could have been placed on Mercury by Comets after that they sugar coated a basalt rock and fired projectiles so see the darkening effect of carbon. This experiment supports the claim that Mercury is covered by carbon dust which were made by passing comets.
The dull surface of Mercury is mysterious and researchers believe that it because the surface is blasted with tiny rich “micrometeorites” which are rich in carbon. Scientists are saying that planet is painted, of course that is only a metaphor but this theory was being hypothesized for the long time and many scientists believed that the darkening agent was a mystery. At that time scientists did not consider the fact that Mercury might have been experiencing lot meteor showers.
Comets are made of ice and rock and are the remnants of the formation of the solar system, they crumble when they reach Sun, the dust that these comets produce are extremely high in carbon.
NASA used a Four meter cannon to launch small particles at pieces of basalt. The projectiles were traveling at a speed of 5km per second and mimicks the situation of a meteor hitting an object. The surface of the basalt became darkened with carbon paint.