Lawrence Livermore National Laboratory | 2015 Mar 30
Peering into space, the surface of Mercury appears dark and unreflective, an observation that has long puzzled planetary scientists due to the planet’s very low surface abundance of iron (less than 2 percent).
Iron is an important darkening material in airless bodies like the moon and asteroids.While the intense space weathering environment on Mercury, which efficiently converts the small amount of available iron into submicroscopic metallic iron, contributes to its dark surface, this effect is not sufficient to explain observations of Mercury’s appearance. As a result, researchers have long speculated that a “mystery darkening agent” must be contributing to Mercury’s dark surface.
In a study published today by Nature Geoscience, a team of researchers investigate, whether carbon, delivered by comets and/or comet dust, could be this elusive mystery darkening agent.
“Our study answers a longstanding mystery about why Mercury’s surface is darker than the moon’s surface, by implicating carbon as a “stealth” darkening agent, which is difficult to detect with available remote sensing methods,” said lead author Megan Bruck Syal, a postdoctoral researcher at Lawrence Livermore National Laboratory. “Mercury is effectively painted black by the constant influx of carbon-rich micrometeorites.” ...
Darkening of Mercury's surface by cometary carbon - Megan Bruck Syal, Peter H. Schultz, Miriam A. Riner
- Nature Geoscience (online 30 Mar 2015) DOI: 10.1038/ngeo2397