once a dust storm actually gets rolling, the entrained dust begins to act like a fluid. So, the density actually increases by way of the velocity and the energy therein is conserved in the particles. The average particle size is waay smaller though .
Thats why all those huge dunes on Mars exist, they are, sorta, like the walking dunes of the Sahara except that Saharan sand storms re usually only about as high as your Knees. The energy equation is unique for each fluid density and we can compute the energy budgets from the dune shapes and sizes.
There isnt much energy being transferred to do damage, since most of the prticles are so small. However, the dust and small sand of Martian storms will abrade like crazy.
Id love to take a trip just to see these forces in action in a whole different environment