K-U ratio

[2] Some elements like potassium, uranium, and thorium are naturally radioactive and give off gamma rays as they decay.

Electromagnetic radiation from these isotopes can be detected by a Gamma-Ray Spectrometer (GRS) dropped toward the planetary surface or observed from orbit.

To determine the elemental makeup of the Martian surface, the Mars Odyssey used a GRS and two neutron detectors.

At the high temperatures for Earth, no volatiles would be in the solid state, and the dust would be made up of silicate and metal.

[5] This difference suggests that the material that formed the Moon was subjected to temperatures considerably higher than the Earth.

Hence, most of the collisional material sent into orbit would consist of silicates, leaving the coalescing Moon deficient in iron.

The more volatile materials that were emitted during the collision probably would escape the Solar System, whereas silicates would tend to coalesce.

The fine-grained matrix which fills spaces between the chondrules, however, appears to have formed at rather different temperatures in the various classes of chondrites.

In these meteorites, chondrules coexist with minerals that are only stable below 100 °C, so they contain materials that formed in both high- and low-temperature environments and were only later collected together.

However, metal/silicate partitioning data for K and U still needs additional experiments at the conditions of Mercury's core formation to understand this unusual high ratio.