Commenting on the first findings by NASA’s MESSENGER probe in orbit around Mercury, The Open University's Dr David Rothery said:
“Mercury is full of surprises. From the views glimpsed during MESSENGER’s 2008 and 2009 flybys it was apparent that vast tracts of the planet are covered by lava flows. Now MESSENGER is in orbit we can see details of volcanic vents and lava channels and begin to determine the surface composition. For me the most intriguing aspects are that Mercury is richer in sulphur and potassium than it has any right to be, so close to the Sun, and the curious hollowed terrain* where steep-sided, flat bottomed pits a few tens of metres deep and up to a few kilometres across show that parts of the surface have wasted away, and presumably by being turned to vapour. Sulfur would be the obvious candidate, except that the colour associated with most of these pits is blue rather than yellow. MESSENGER probably won’t be capable of measuring the composition of features this small, so this is something for the European and Japanese Space Agencies’ BepiColombo mission to get its teeth into, when it arrives in 2020.
“When NASA, ESA and Japanese Space Agency Mercury teams met in Kyoto last month, there was much excitement and speculation about what the new results might mean. Maybe Mercury formed much further away from the Sun than its current orbit (nearly three times closer to the Sun than the Earth) and migrated inwards later. On the other hand, Mercury has a very large iron-rich core, so maybe there was something about the catastrophic giant collision responsible for stripping away most of Mercury’s original rocky mantle that was able to scavenge sulfur and potassium from the core and concentrate it upwards as the new crust formed.”
Dr David Rothery (Planetary & Space Sciences Division at The Open University) heads the European Space Agency’s Mercury Surface & Composition Working Group and is the lead scientist for the X-ray spectrometer that will be flown to Mercury on ESA’s BepiColombo mission (to be launched in 2014).
The first results of the MESSENGER probe were published in Science today (30 September).
* Hollows on Mercury: MESSENGER evidence for geologically recent volatile-related activity, Blewett et al., Science, vol 333, p.1856-1859