One day, we'll bring samples home from Mars — but, until then, we have to make do with what we've got. Fortunately, we actually have some Martian material to work with, thanks to meteorites from Mars that crashed into Earth.
Sure enough, scientists with the University of California, San Diego's Scripps Institution of Oceanography are studying these meteorites, and have indeed gained insight into the early formation of the Red Planet. Specifically, they've gleaned information about the structure of Mars' crust and mantle. The meteorites indicate Mars has an atmospherically altered upper crust as well as a complex deeper crust; they also suggest it has a mantle from which plumes emerge through the crust to produce a specific type of volcano. The meteorites have also indicated that Mars has discernible reservoirs throughout its internal structure.
