 MMS, however, was hygroscopically inert due to minimal weathering and the way it was crushed, which allowed it to better simulate that feature of Martian regolith, among others.MMS was found naturally as whole rocks in a volcanic formation near the town of Boron, California, in the western Mojave desert.After crushing, basalt sands were processed and graded into particular sizes, MMS Coarse and MMS Fine.