Compositions of coarse and fine particles in martian soils at gale: A window into the production of soils

•Martian soils are analyzed for the first time at sub millimeter scale.•Three different groups of coarse grains have been distinguished.•Fine particles seem to derive from one group of coarse grains.•Presence of amorphous component in fine particles and some coarse grains.•Fine particles have undergone limited interaction with water.