Interesting that the 'clumps' are on one leg only. One theory is that dust and ice were blown onto the leg during landing. If the regolith does indeed have the rather impressive thermal inertia properties implied by the presence of well bonded permafrost only 2 cm down, then any regolith dust deposited on the leg could insulate ice that deposited on top from any heat transfer from the leg. We would therefore have a perfect shaded and cold location for frost to deposit and resist sublimation - so the clump would grow.
