Using Earth's Magnetic Field to Characterize Materials
Though we may not think about it much, we are all aware of Earth's magnetic field. The most obvious use of it is to orient compasses, but it has other uses too, as it is used for probing in geology and archaeology. Thanks to researchers at Berkeley Lab, it may soon also find use for analyzing chemical compositions of fluids, without removing them from their native environments.
Nuclear Magnetic Resonance (NMR) is a phenomenon that can be used to determine the materials in some sample, and possibly its most common use is medicine's MRI machines. It works by measuring how atoms behave when the angle of their spins are manipulated. Normally strong and uniform magnetic fields are used, but these are not always available. What is always available on Earth though is the planet's magnetic field. Attempts have been made before to use the Earth's magnetic field for NMR, but failed because the field is so weak and the equipment was not very sensitive. The Berkeley researchers have discovered that it appears to be possible now, by using highly sensitive optical magnetometers and by looking at how the spins of molecules relax and diffuse.
Potentially this technique could be used to characterize the contents of solids underground, such as in oil wells, and actually measure hydrocarbons and water within rock, as well as inspecting the curing process of polymers and cement. The researchers next want to increase the depth their method can reach inside of a material, possibly piercing a meter or more, instead of the inches possible with current technologies.
Source: Berkeley Lab