Dark Stains on Mercury Reveal Its Ancient Crust

Ever since the MESSENGER spacecraft entered orbit around Mercury in 2011, and indeed even since Mariner 10‘s flyby in 1974, peculiar “dark spots” observed on the planet’s surface have intrigued scientists as to their composition and origin. Now, thanks to high-resolution spectral data acquired by MESSENGER during the last few months of its mission, researchers have confirmed that Mercury’s dark spots contain a form of carbon called graphite, excavated from the planet’s original, ancient crust.

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Mercury’s Many Colors

Although composited from expanded wavelengths of light, this wide-angle image from NASA’s MESSENGER spacecraft shows the amazing variation of colors and tones to be found on Mercury’s Sun-scoured surface.


This scene lies between Mercury’s Moody and Amaral craters, spanning an area of about 1200 km (745 miles). The patch of dark blue Low Reflectance Material (LRM) in the upper left of the image and the bright rayed crater on the right make this a diverse view of Mercury’s surface. Note the curious small, dark crater just below the bright rayed crater on the right.

Dark LRM material is thought to indicate the presence of a mineral called ilmenite, which is composed of iron and titanium and has been revealed through volcanic, cratering and erosion processes.

More Mercury images: Postcards from the (Inner) Edge

Did you know that until MESSENGER arrived in 2008 half of Mercury had never been seen? And that although Mercury is the closest planet to the Sun there may still be water ice on its surface? Learn more about these and other fascinating facts about Mercury here.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington