Geology of Mars of the dichotomy places a significant constraint on theories of its origin. Straddling the dichotomy boundary in Mars's western hemisphere is a massive volcano-tectonic province known as the Tharsis region or the Tharsis bulge. This immense, elevated structure is thousands of kilometers in diameter and covers up to 25% of the planet’s surface. Averaging 7–10 km above datum (Martian "sea" level), Tharsis contains the highest elevations on the planet and the largest known volcanoes in the Solar System. Three enormous volcanoes, Ascraeus Mons, Pavonis Mons, and Arsia Mons (collectively known as the Tharsis Montes), sit aligned NE-SW along the crest
Olympus OM system the film plane. The combination of on-lens aperture control and the generous 'flange focal distance' make OM lenses adaptable (with limited functionality) to a variety of other camera systems – including Canon EOS models – by using a mount-specific adapter. Manual Zuiko lenses that were never marketed: Being a system, Olympus made numerous accessories for professional portrait, photo journalism, sport photography and scientific photography. Olympus OM system The Olympus OM System (O = Olympus, M = Maitani) was a line of 35mm single-lens reflex cameras, lenses and accessories sold by Olympus between 1972 and 2002 (some accessories were sold until