My physics buddy and I have been having a debate. I was claiming that even under the natural Earth's magnetic field that with good signal to noise ratio based on the radar systems scaled appropriately the top layers of the Earth could be seen. He claimed that the signal to noise ratio of the T1 and T2 echo reply would be too low. Is thermodynamic noise too great for this task even with adaptive noise cancelling technologies? We were studying the Na2+ ion for Earth Gauss levels of magnetic field and the NMR and ion cyclotron resonance frequencies and intensities. Has anyone run the equations and what do you think? Is it possible?