re: Can MARSIS even distinguish between ice and rock that well? False negatives could be saddening, indeed.
"To first order, rock and ice have similar dielectric properties."
Sure, similar electric permitivity but not magnetic permeability. Index of refraction couples both so it's more complicated than just absorbtion. It's concievable that a burried, pure ice lense could be detectable even if it has a similar permitivity. The thing that isn't well known I guess is the factor that the permeability will play relative to premitivity. Like Gary Olhoeft brought up at GeoMars, any place with magnetic dust is going to have some magnetic contribution.