Wait, but airport scanners HAVE reached this type of analysis level—the only problem is that do so the x-ray emitter has to rotate around the bag (or the car in this instance) to create a 3D model of the objects within, which is then used to estimate density to a high degree—and from there things became much easier.
Of course, they’re used to analyze bags, not cars, and the objects have to pass within...but still
A 3D density map does not reveal the chemical structure by itself.
Since you also have the X-ray spectrogram of the material, you can narrow down the materials that have the same spectrogram but different densities—i.e. organic compounds and water