An Asymmetrical Planet - The Martian Mantle

 Measurements of Mars's gravity field, topography, and the subsequently
 derived crustal map show the Southern Hemisphere to be significantly 
 thicker than the North.

Gallery 
Science Stories
http://svs.gsfc.nasa.gov/stories/MOLA/

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              FURTHER REFERENCES

 GO - "search perceptions" - in SEARCH-ENGINE


file-ID www.perceptions.couk.com/uef/marsmoon.txt