Use suspension bridge technology to place large sheets of double paned glass or fuzed quartz over narrow canyons. Slowly pressurize the living space under the quartz ceiling with Martian atmosphere using turbopumps. As the glass/quartz ceiling over the canyon bows out from gas pressure, allow heated water to flow between the panes of glass/quartz. Eventually the space between the glass is fully filled with recirculating heated water. The mass of the water between the glass balances the pressure of the gas underneath. The original suspension bridge technology remains as a backup against accidents. The water between the glass provides heating and shields against secondary cosmic rays. Sunlight passing through the glass/quartz illuminates the land underneath which is used for agriculture. The plants are watered from nozzles overhead leaking water from the glass ceiling (artifical rain). The heat for the water is provided by multi-gigawatt nuclear reactors. The glass ceiling acts as a cooling tower for the nuclear reactors to reject waste heat through convection and radiation. The habitate atmosphere is based upon continuous gas replacement and is not a sealed environment. Fresh Martian atmospheric gas (carbon dioxide) is being continually pumped into the habitat. Agriculture converts the carbon dioxide into oxygen. Constant pressure is maintained through controlled leakage. System is self sealing through water ice. Gas in habitat is at one bar, 20 deg.C and fairly humid. Humid gas leaks to the Martian atmosphere by expanding from one bar pressure to 6 millibars. The sudden drop in pressure causes large drop in temperature that in turn causes water vapor to condense out as ice. The ice fills up leak until it is a tiny hole. The system requires a reliable high power energy source. Liquid metal breeder reactors or nuclear fusion are possible options.

Gary