Conclusion: The Deep Frontier
When Raymond Davis, Jr., a nuclear chemist, decided to build an experiment deep underground to search for neutrinos from the sun, and Masatoshi Koshiba, a particle physicist, similarly sought shelter from the cosmic rays in order to look for the decay of the proton, few people anticipated just how surprising those experiments would be. Recognized by the award of a Nobel Prize, they gave birth to modern neutrino science and revolutionized physics. In 1987, underground detectors registered for the first time the huge burst of neutrinos emitted by a supernova and confirmed the understanding of the way stars explode. A subsequent generation of underground physics experiments in Europe, Japan, and Canada established that neutrinos have a non-zero mass, thereby resolving the puzzles exposed by earlier results and opening a totally new field of study in particle and nuclear physics.
It is not a wild extrapolation of history to assert that deep underground research will similarly contribute to answering critical questions of 21st-century science and engineering. Discoveries will come not only in physics and astrophysics, where scientists will explore the properties of neutrinos and the nature of dark matter, for example, but also in biology, where research will include the investigation of the genome and evolution of subsurface microbes. Earth scientists will map the mechanisms responsible for the deformation of the earth's crust, and engineers will characterize the strength of large rock mass and the transport of fluids. Moreover, as in the serendipitous discovery of supernova neutrinos by proton-decay experiments, investigations with powerful underground instruments can expect to encounter totally novel phenomena.
It is clear that an important frontier of modern science is underground. A systematic and coordinated approach to underground science will lead to significant scientific progress. There is also much to be gained by bringing together scientists from different fields whose paths might otherwise rarely cross. Underground research has the potential to have a large positive impact on our economy, environment, education and well-being. Deep underground science and engineering represents a remarkable opportunity for the U.S., best pursued through a Deep Science Initiative. Such an initiative would focus expertise of multiple fields of science to solve key problems. It would maximize the use of existing facilities and international collaborative opportunities and complement the existing infrastructure with a very deep underground laboratory designed to attract the best experiments from across the world.
