I find the lack of iron to be curious, exactly the opposite to what I had expected. I'm not sure just how much iron I expected, but this finding is surprising to me, much lower than anything I had thought of.

It makes me want to now consider a lander with analysis instruments similar to what's happening on Mars now. I wonder what the surface conditions are like at the poles? Equatorial and mid latitudes landing sites are obviously out of the question for now, but it may well be possible to place a lander in the arctic or antarctic regions of the planet. Temperatures and surface conditions there are more likely to be tolerable for lander operations and survival.

What is more surprising is that NASA and its scientists are surprised about vulcanism on Mercury, or on any terrestrial body for that matter. What do they think a primal ball of lava will do when it is first formed?

Close to the Sun, we might expect that lighter elements will be less common due to solar wind and heating effects, so the bodies that formed Mercury will be iron-rich inside, but the lack on the surface is puzzling. However, any terrestrial planet should (and will, in my opinion) have volcanos at some point in its history. How else will heat and volatiles escape from the interior as it settles and segregates?

Chuck,

The supposition is that Mercury HAS a great deal of iron, but it is sequestered in its large metallic core (that generates the global magnetic field) and thus, iron is depleted in the outer crust and mantle of Mercury. Moreover, this putative "lack of iron" is all relative to the Moon's surface, which has anomalously iron-rich lavas (the dark maria).

To anyone smarter than I:

Could Mercury have been subject to internal tidal heating (from the Sun's gravity) in the same manner as Io? Perhaps the planet's orbit was more eccentric at one time?

Thanks for any feedback,
Eric Fischer