The planetary body that Spirit was designed to explore the wide ranges of soil and rocks for clues of the water activity on Mars. Spirit specifically landed at the Gusev Crater which was before, a possible lake in a giant crater.
One of the differences between the cell membrane and the cell wall is in the type of organisms that they are found in. A cell wall is found in plants only. A cell membrane is found in all organisms including plants. Present only in plants, and in some fungi, bacteria, algae.
