Executive Summary
As any subway rider can attest, the world is different underground. It’s dark, conditions are often extreme, and unusual forms of life emerge. Even deeper beneath the earth’s surface, closer to the level of Jules Verne than of the F train, the world turns very different indeed.
Deep down, at the depth of a few kilometers, the chatter of invisible cosmic rays entering the earth’s atmosphere fades to a hush. Temperatures rise, pressures increase, and the environment becomes salty and alkaline. Novel life forms, cut off for millennia from the earth’s surface, eke out their existence in the darkness. And everywhere there is the rock, with its fractures and faults, its water networks, its stresses and strains, its slow movement and sudden cataclysms. Like a voyage to Mars, going underground is a trip to a different world. It’s a world that scientists from a variety of fields would like to make their own.
To discover the mysteries of the universe takes some digging—literally. It might seem counterintuitive, but answers to some of the most compelling questions about what’s going on in the farthest reaches of space and time are likely to come not just from Out There, via telescopes and space probes, but from Down There, in experiments planted in the rocky depths of planet Earth. As a result, growing numbers of scientists in the U.S. and worldwide are going underground.
Source: CERN
Twenty-first-century particle and nuclear physicists and cosmologists define their science by a set of questions about the universe, some as old as humanity’s quest to understand nature’s laws, some prompted by recent discoveries. What happened to the antimatter that was almost certainly present at the Big Bang? What story do neutrinos, the slipperiest characters of the particle world, bring us from that ancient time when physical laws we no longer see ruled the universe? What are the invisible dark matter and dark energy that comprise more than 95 percent of everything that exists in the universe? Do all of nature’s forces ultimately combine? These questions have excited physicists not only because of their compelling nature, but because, for the first time, the technological means appear to be at hand to discover the answers. The combination of observations in space, experiments at particle accelerators, and experiments underground promise, over the next few years, to change the picture of the universe beyond our wildest imaginings. Underground research will play a key role.
Why underground? Because it’s quiet down there. We can’t hear the commotion, but to the particle detectors that are the eyes and ears of physics experiments, the noise on the earth’s surface sounds like a boiler factory. Detectors are immersed in the constant bombardment of cosmic rays. For a critical set of physics experiments, the surface noise drowns out the pin-drop signals that are physicists’ clues that they’re onto something. To hear the whisper of discovery, physicists need shelter from the cosmic racket. Which is why they are ready to start digging.
Below the surface, the noise fades as rock absorbs the particles from space. The quiet deepens as the depth increases, the cosmic-ray rate decreasing tenfold for every 300 meters of rock. Cosmic rays do not penetrate much more than 4000 meters. Even at 2000 meters, much of the cosmic chatter is stilled so that experimenters can pick out the subtle signatures of neutrinos. They can look for the rare, solitary flash that would signal a proton’s decay—and a whole new vision of nature’s particles and forces. Sheltered by the earth’s crust, scientists can tune in to the tiny but unmistakable signals of a revolutionary new physics of the universe.
Physicists and astrophysicists have a strong tradition of underground research. However, there is an emerging consensus that underground facilities also play an important role in addressing key questions in biology, geoscience and engineering.
Although half of the earth’s biomass lives below the earth’s surface, some of it in the hot, dark, rock-bound environment at depths of five kilometers or more, underground life remains largely unknown. How do these microbes live in conditions that, from our surface perspective, would seem to make life improbable? How have they evolved, isolated for millennia from surface organisms? How do they alter the geology and chemistry of the subsurface? What can they tell us not only about life at the extremes here at home, but about life as it might exist on other planets? Deep underground, is there life as we don’t know it? Biologists need sustained access to deep pristine environments, uncontaminated by mining operations and with the best possible control of drilling operations, to discover the nature of life at the underground extreme.
Source: DUSEL S1 Study
Geoscientists, in turn, see sustained access to large volumes of deep subterranean rock as an opportunity to address central questions in modern earth science. Can we understand and predict catastrophic natural events, especially earthquakes? How do material properties control processes in the earth’s crust? Although geoscientists make use of opportunities afforded by mining operations, they dream of underground research facilities wholly devoted to science. Similarly, underground engineers anticipate that building and working in a dedicated underground laboratory will take them far in their quest to develop a “transparent earth,” whose now-opaque mass might one day become transparent to observers. The increasing strategic value of underground space to meet the needs of our shrinking planet gives urgency to their efforts.
Physicists, astrophysicists, biologists, geoscientists and engineers all have their own scientific reasons for heading beneath the surface. They also anticipate a unique scientific synergy when scientists from diverse disciplines, whose surface paths don’t often cross, join forces underground. Can we use the techniques of particle detection to probe the earth’s core? What will we learn about rock mechanics and underground construction from building underground spaces for gigantic particle detectors? Who knows what cross-disciplinary insights will spring from lunch-table discussions underground?
RECENTLY, a nationwide cross section of researchers have examined the scientific potential of deep underground science and engineering. In a two-year study, they developed requirements for a strong U.S. program in underground research. “Deep Science” presents their findings and recommends a cross-agency Deep Science Initiative to expand and coordinate current programs, make use of existing U.S. underground facilities, and continue strong international collaboration. Although certain experiments can be performed at intermediate depth, they conclude, the scientific frontier is deep down at a depth of approximately two kilometers.
While most developed nations have carved out space for underground laboratories, in mines or under mountains, underground research space is severely limited in the U.S. There is no U.S. site below one kilometer deep. In response, “Deep Science” proposes the development of a Deep Underground Science and Engineering Laboratory to complement existing domestic and foreign laboratories and promote international collaboration. DUSEL would provide the U.S. with powerful underground scientific capabilities. At a time of growing concern about the erosion of U.S. scientific and technical leadership and its effect on future prosperity, the Deep Science Initiative would lead to scientific discovery and encourage technological innovation. While initially motivated by physics and astrophysics research, it would have important additional benefits for other fields of science. It would provide a unique research environment to inspire and educate the nation’s next generation of scientists and engineers.
Dig we must, for a greater understanding of the universe and our place within it.
