Mercury's volcanism

Image of Mercury from the MESSENGER's second flyby in 2008.  Image from NASA/JHUAPL.

The images and preliminary science results from MESSENGER’s third flyby of Mercury are trickling out. The BBC had an early report and here’s the mission press release. There are many interesting findings, but the discovery of geologically recent volcanism seems particularly striking.

MESSENGER mapped volcanic structures during its first flyby in January 2008. These features included vents, flows, and collapsed magma chambers and were reported in a special issue Science dedicated to MESSENGER on July 4, 2008 by Head et al. (abstract only).

Image and map of the largest (as of 8/19/2008) identified Mercutian volcano. See the mission website for a complete description. Image from NASA/JHUAPL.

Even better, the newest flyby shows evidence for volcanism <1 billion years old, manifested as smooth flows covering the floor of a double-ringed basin. A billion’s a lot of years, but prior to this Mercutian volcanism was only known to be as young as 3 billion; this significantly extends the activity. Also of interest is evidence for vent-related explosive volcanism (for which I don’t know the relative age) – this requires volatiles in the magma and might tell us something about the mantle.

False color image courtesy of NASA/JHUAPL. The double-ringed impact basin is ~290 km across and the smoothness of the floor is thought to be due to basalt flows. The yellow material in the upper right is composed of pyroclastic volcanic deposits. The mission website has a more complete description.

Other new data suggest the surface of Mercury is rich in non-silicate Fe-Ti minerals (maybe ilmenite), similar to high-Ti Lunar mare basalts, as described here. There are findings on Mercury's magnetism, partially liquid core, and more from this and previous MESSENGER flybys, but I don't have time to get into it all now. This is all pretty new to me so I'm scrambling to catch up.