Planet Mercury’s dark surface was formed by a constant dusting of carbon brought from passing comets, according to a new study.
According to the research, Mercury reflects very little light, while its surface has a very low content of iron. This fact excludes the presence of iron nanoparticles, which is the most likely “darkening agent”.
In the new study, researchers measured how much carbon-rich material could have been discarded on planet Mercury by passing comets. Then, the scientists fired projectiles at a basalt rock, covered in a sugar coating, in order to confirm the darkening effect of carbon.
Their results, which were published in the journal Nature Geoscience, support the theory that Mercury was “painted black” by dust from passing comets over billions of years. The team says that the effect of being “showered” with tiny, carbon-rich “micrometeorites” is more than sufficient to explain the mysterious, dark surface seen on Mercury.
“It’s long been hypothesised that there’s a mystery darkening agent that’s contributing to Mercury’s low reflectance,” said the paper’s first author, Dr Megan Bruck Syal from Lawrence Livermore National Laboratory. “One thing that hadn’t been considered was that Mercury gets dumped on by a lot of material derived from comets”, she added.
Comets are the icy rocks which travel trough space as left over from the formation of the solar system. Comets often start to crumble as they approach the Sun. The dust they produce is almost always very rich in carbon. Some measurements put the figure to up to 25% by weight, a level which the researchers simulated with sugar grains.
With the help of a four-metre cannon at the Nasa Ames Vertical Gun Range, the team launched very small projectiles, travelling at speeds of over 5km per second, at pieces of basalt, which is similar to moon-rock.
When the basalt was mixed with sugar, which melts with the impact to produce carbon, its surface became darkened with a “paint” that was very rich in carbon. The scientists believe that explains what happened to Mercury’s surface.
The results were less impressive when the basalt was mixed with sand instead of sugar.
“It appears that Mercury may well be a painted planet,” said Prof Peter Schultz, a co-author from Brown University on Rhode Island, according to BBC.
Image Source: Motherboard
