Because the constitutive laws for soils are governed mainly by interparticle friction, all aspects of their mechanical behavior depend strongly on gravitational body forces. This fact poses serious limitations on the formulation of a materially objective soil constitutive theory, based on experimentation performed on earth. In particular, the presence of the earth\u27s gravity prohibits the design of controlled experiments to properly simulate a variety of critical phenomena associated with the dynamic response of soils to seismic excitation in a very low effective confining stress field. For these reasons, the advent of the space age and, more specifically, the capabilities of the Space Shuttle-Spacelab for several day experimentation by trained specialists in a shirt-sleeve, laboratory- controlled environment, under essentially zero-gravity conditions, could offer invaluable opportunities for developing a quantitative understanding of fundamental aspects of soil behavior during and after an earthquake, which, in turn, could result in significant technological advances in geotechnical earthquake engineering
