Mercury's magnetic field contains magnetic cusps, areas of focused field lines containing trapped magnetospheric charged particles that will be funneled onto the Mercury surface at very high latitudes and direct energetic protons, ions and electrons directly onto ices in the polar regions.

Energy deposition onto the ices comes from magnetospheric charged particles, galactic cosmic rays (GCR), solar energetic particles (SEP) and Lyman-alpha and scattered UV photons.

This focused radiation will initiate chemistry that may create dark compounds that could be the dark low-albedo materials observed by MESSENGER instruments. Thick layers will be created by radiolysis and chemistry as well as gardening, overturn, sputtering and other physical processes occurring simultaneously.

Complex CHNOS molecules may be created by this process, such as aldehydes, amines, alcohols, cyanates, ketones, hydroxides, carbon oxides and suboxides, organic acids and others. Specific compounds are: H₂CO, HCOOH, CH₃OH, HCO, H₂CO₃, CH₃C(O)CH₃, C₂O, C_xO, C₃O₂, C_xO_y, CH₃CHO, CH₃OCH₂CH₂OCH₃, C₂H6, C_xH_y, NO₂, HNO₂, HNO₃, NH₂OH, Na₂O, NaOH, HNO, N₂H₂, N₃, HCN, CH₃NH₂, SO, SO₂, SO₃, OCS, H₂S, CH₃SH, even B_xH_y.

Magnetospheric energy sources dominate the energy flux onto the ices. The total energy fluxes of photons, GCRs and SEPs are each around two or more orders of magnitude less than magnetospheric fluxes. GCR and SEP have lower fluxes but will process deeper layers of the ices because of their greater depth of energy deposition.