MESSENGER reveals Mercury's volcanic surface

Brett Smith for redOrbit.com – @ParkstBrett

Since 2011, NASA’s MESSENGER probe has been orbiting and gathering data on Mercury and the latest published research based on mission data has revealed never-before-seen features on our Solar System’s third planet.

What makes these geological formations unique is their unique chemical make-up that appears to have its origins not in the planet’s crust, but deep below the surface in its mantle.

One recent study, published in the journal Earth and Planetary Science Letters, used data from MESSENGER’s X-Ray Spectrometer (XRS), which generate the first comprehensive geochemical maps of Mercury. The device takes advantage of X-rays coming off the Sun’s surface to analyze the chemical composition of the planet’s surface.

Volcano-shaped terranes

The most apparent of these unusual formations, also known as terranes, is a massive expanse that covers more than 3 million square miles of the planet’s surface. This terrane displays the highest detected silicon ratios on the surface. The study also revealed extremely high aluminum-to-silicon ratios. The study speculated that this could have been caused by a massive impact that was then “healed” by an exposed mantle.

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Another recent MESSENGER study, published in the journal Icarus, utilized data from the probe’s Gamma-Ray Spectrometer (GRS) to find four distinct geochemical terranes on the planet. One planetary feature in particular, known as the Caloris impact basin, was found to have a geochemical makeup very different from other volcanic plains on Mercury. These plains, the study noted, are formed by a partial melting of the mantle.

“Earlier MESSENGER data have shown that Mercury’s surface was pervasively shaped by volcanic activity,” said Patrick Peplowski, of the Johns Hopkins University Applied Physics Laboratory and lead author on the second study.

“The magmas erupted long ago (and) were derived from the partial melting of Mercury’s mantle,” he said. “The differences in composition that we are observing among geochemical terranes indicate that Mercury has a chemically heterogeneous mantle.”

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“The crust we see on Mercury was largely formed more than 3 billion years ago,” said Larry Nittler, deputy principle investigator on MESSENGER and co-author on both studies. “The remarkable chemical variability revealed by MESSENGER observations will provide critical constraints on future efforts to model and understand Mercury’s bulk composition and the ancient geological processes that shaped the planet’s mantle and crust.”

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