To quote 18th century geologist James Hutton, "the present is the key to the past." A paradigm that proves itself effective, even in cases of extraterrestrial geology. Exclusively through remote sensing techniques, scientists have begun unraveling Valles Marineris' past and are one step closer to finding possible signs of life on other planets, however remote they may seem. Probably the most likely creation scenario is a combination of all three of the major theories present, in which case future researchers will certainly have their work cut out for them.
Suggested areas for future study would include a reexamination of all results already obtained, with an effort to enhance and improve them with new visual, mineralogical, and altitudinal data streaming in from the Mars Odyssey and Mars Global Surveyor probes. For example, the ability to correlate rock assemblages based on mineralogical similarities instead of purely visual ones should open up a whole new realm for observation.