Posted by & filed under 2012 / 2013 Field Season.

Katie Joy、Recon Team, 27th December 2012, Graves Icefields

Predictably today the katabatic wind is still blowing hard from the south at about 30-35 knots preventing us from moving campsite to a new icefield, and once again we have been tentbound. It is incredibly frustrating to not be productive, but we have been occupying ourselves sleeping, eating (lots of eating) and reading to fill the time so not to go loopier than we already are (see the funky glasses photo from Christmas day as proof of our increasing bonkersness!). As my PC died a few days back I have been digesting a biography of the Norwegian arctic explorer Fridtjof Nansen, who was the first to lead an expedition across Greenland and led the trail for the early Antarctic explorers Amundsen, Scott and Shackleton. What a change in technology between now and then – thank goodness for not having to eat a daily ration of pemmican (mix of dried meat and fat) – Tomoko and I had tasty steak and mashed potatoes for dinner tonight cooked on our propane stove.

As there is little to report on the meteorite searching front, I thought I would postulate on a type of meteorite that would be incredibly scientifically interesting to find – a piece of the planet Mercury. Mercury is the smallest planet in the Solar System (0.05 of the Earth`s mass) and closest to the Sun. The planet has differentiated with a very large dense metallic core (perhaps up to 75% of its radius) and a correspondingly thin crust. Mercury was visited by NASA`s Mariner 10 flyby mission, and is currently being mapped in detail by NASA`s MESSENGER mission and will be visited in the 2022 timeframe by the European Space Agency`s BepiColumbo mission.

Mariner and MESSENGER have revealed that Mercury`s surface has been heavily cratered by impact events, and that younger volcanism has covered some regions (notably the northern plains) with lava flows. We are learning a huge amount from these orbital missions, but it would be incredibly useful to have a piece of the planet Mercury we could study in our labs to determine its precise age, mineralogy, chemical makeup and isotope abundance. For example, such studies may reveal if the planet was formed in its current orbit close to the Sun, or if it is a body that was formed elsewhere in the Solar System and wandered in to its present location. Testing these scientific hypotheses are important for informing us how planets and Solar Systems form and evolve through time.

Could there be pieces of Mercury here on Earth as a meteorite? Although it is dynamically difficult for impact ejected pieces of Mercury to be thrown into an Earth-crossing orbit that would allow it to fall here as a meteorite – according to some computer models it is not impossible, and, therefore, there is a chance (albeit a small one) that there is a piece of Mercury out there somewhere waiting for us to find in Antarctica.

So how could we identify a piece of Mercury? Results of the MESSENGER mission X-ray fluorescence spectrometer (XRS) and gamma-ray spectrometer (GRS) have given us great insights to the chemical composition of the upper surface of Mercury that can be used to match with new meteorites that we find. We now know that Mercury`s surface is not chemically similar to the Moon in terms of aluminium or potassium. The XRS instrument also showed that the planet`s surface is poor in iron and titanium, but has some sulphur present – suggesting that these rocks were formed under low oxygen conditions. Also Mercury`s crust has relatively high Mg/Si ratio – and is compositionally similar to a type of magnesium-rich lava known as komatiite that flowed on the early Earth. It is also similar to some meteorites that have large amounts of the magnesium-rich mineral enstatite, although there is not a perfect compositional match with any of these samples. Thus, Mercury`s surface appears to have a unique chemistry that is distinct from most known meteorite groups and other planetary surfaces. Therefore, if we can find a meteorite that matches these compositional constraints – there is a good chance that we have a piece of the planet Mercury available to study in more detail here on Earth.

With all the bad weather the recon team have been having – we are due some better fortunes, and perhaps a mercurian meteorite is awaiting us at the next icefield?!

PS. We hope that if you in the middle of writing an LPSC abstract it is going well.