What are the sedimentary rocks on Mars made of?
In Meridiani Planum (as well as Gusev) the sediments were mostly gypsum. This is technically knows as calcium sulfate, and is the same material that wallboard and Plaster of Paris are made of. There is also lots of iron oxide and salts mixed with the material, making it soft and crumbly. What is the soil on Mars made of? For the most part, it is not very different from terrestrial soils, but it is mostly silica sand, iron oxide, volcanic material and ash, and lots of gypsum dust with various salts. In some places, the soil is half salt- in particular magnesium sulfate or Epsom salts with a mixture of sodium chloride and other materials like iron sulfate. As much as 2% to 5% of the Martian soil is carbonate dust. Epsom salts is hydrated, containing half its weight in water, and gypsum is also hydrated, containing about 10% of its weight in water. What is the white powder in the rover wheel tracks? Fine crystals of salt from the briny water under the soil. When this water is squeezed out
