Author: Josh Knackert
Monday, October 15, 2018
A technician was working in an approximately 500 cubic meter neutrino detector during construction in April-one of two liquid argon detectors built at the CERN facility near Geneva, Switzerland. CERN’s detectors, collectively called ProtoDUNE, are prototypes of four larger versions that will be built at the Sanford Underground Research Facility (SURF)-the former Homestake gold mine near lead near SD-as deep underground neutrinos Part of the experiment (DUNE)). Credit: CERN.
On a cold day in northern Minnesota, the historic iron mine of Sudan. The mine ceased operations in 1962 and now operates as a state park and conducts scientific research. Credit: Josh Nakert.
On a cold, icy day in northern Minnesota, around 5 am — on a day that feels like your eyeballs might freeze — a group of about 10 undergraduates in the University of Minnesota-Duluth geobiology course Sheng jumped on a bus and went to a destination that was gentler and farther away from the elements—or rather, in the depths of the elements. Accompanied by their professor, microbiologist Cody Sheik, geologist Latisha Brengman, and some others (including your real members), the students arrived at the Visitor Center and History Museum in Northwoods, Minnesota in two hours . Sudan iron ore. The mine began operations as an open-pit mine in 1882, but moved underground about 20 years later and ceased mining in 1962.
After hurriedly entering the (warm) visitor center to watch a video about the mining operation 800 meters underground in Soudan, everyone on the team put on hard hats and headlights for three minutes of pitch-darkness and claustrophobia The induced descent takes the loud, clinking elevator car into the mine-the original mine elevator was built around 1900. Then take the original mine railway for more than one kilometer to reach the deepest part of the mine, and then take a guided tour.
The mine and its history are fascinating, as is the buried ore exposed on the mine walls-a banded iron formation with thin layers of black and red rock vortexes through which white quartz veins pass. But on this day, the students and their mentors visited the mines not to appreciate some eye-catching Precambrian geology, or to shelter from the cold. There is science to do.
As part of microbiology research, Sheik and his collaborators have traveled to Soudan many times, and because of the simple sampling technique they used, Sheik and Brengman regarded this trip as an excellent learning opportunity for students. The team spent a day collecting samples from a stream flowing along the side of the mine tunnel. The water is dyed bright red, as is the case with almost all other surfaces. The color is that iron oxidizes when exposed to the air in the tunnel, basically making the entire mine rust. The trickle of groundwater flowing down the tunnel wall condenses this iron oxide in the stream, making the red color exceptionally sharp. At the same time, the riverbed showed a mixture of orange, yellow and brown, almost as if someone had painted oil along its length. These bright mottled stripes—formed by microbial mats—are of the greatest interest to Sheik and Brengman. The team sampled the stream and its population—filtered suspended microorganisms from the water and scraped off some of the slimy biofilm and mineralized solids in the microbial mat—and brought them back to their university laboratory. Sampling is part of a larger effort, not only to study the collection of microorganisms that live in deep tunnels in mines today, but to solve long-term questions about the origin of life on Earth.
With the exception of Sudan, a variety of surprisingly groundbreaking research - and often impossible - research is being conducted underground around the world, from natural resource surveys, seismic activity and carbon sequestration, to less obvious topics such as How did the development of biofuels and life on Earth begin — and, perhaps, the same on other planets. The root of this modern research work lies in mining: Centuries of ingenuity has allowed us to go deep into the earth, and scientists have realized that deep underground and isolation provide conditions and phenomena that cannot be provided by natural or artificial laboratories on the surface. This still applies today, and established underground research facilities provide scientists from many fields with unique ways to answer some of the biggest scientific questions.
Students at the University of Minnesota-Duluth collect samples from a stream in an underground tunnel in the former Sudan Iron Mine. Image source: K. Cantner.
Around the world, there are approximately 20 deep underground laboratories — 10 in Europe and 4 in the United States — buried at depths ranging from a few hundred meters to a few kilometers. Most of them are former mines, although some have been excavated for research purposes only. One of the laboratories is the Large Hadron Collider of the European Organization for Nuclear Research near Geneva, Switzerland. It is probably the most famous underground laboratory facility, buried at a relatively shallow depth of about 100 meters. For about the past 60 years, researchers from different fields have been attracted to underground facilities for many of the same reasons.
One benefit of underground mines, especially for physics research, is that thick soil and rock layers provide what can be called statistically quiet, blocking or attenuating background signals that exist on the earth’s surface, such as solar radiation, which often To be submerged or otherwise interfere with the target signal. For example, one and a half kilometers of ground cover can reduce the noise from cosmic rays by about 10 million times. Physicists often further shield their underground experiments by wrapping detectors in water, lead, or other protective materials to prevent trace amounts of radiation from rocks or even humans.
Another benefit is that underground environments like mines usually stay the same for longer than surface environments. In some deep mines, such as the gold mine in South Africa, the same groundwater can stay in a small area for millions of years; the temperature is also very consistent, always above the freezing point. (The Soudan Mine guide emphasized that this is an activity that attracts tourists throughout the year-the temperature hovers around a comfortable 10.5 degrees Celsius, which is cooler than the sultry summer of Minnesota and much warmer than the cold winter.) In addition, some mines are located in earthquakes. The least active areas reduce their vulnerability to ground vibrations. These relatively stable conditions mean that underground research facilities can last a long time.
The limits of oxygen, organic carbon, and sunlight deep underground provide conditions that are thought to be similar to when early life on Earth began. The underground environment also provides analogues for the conditions under which life may begin on other planets, such as Mars. Along with high pressure, and sometimes even very acidic or dry conditions, these factors create an environment that usually makes it difficult for anything to survive, let alone thrive. However, even in such places, bacteria and archaea called extremophiles are indeed thriving. These microorganisms may be the closest relatives to the microorganisms that originally inhabited the earth.
Given the limitations of the mine environment, in Soudan, Sheik and his team discovered a surprisingly complex microbial community. The inherent resilience of these creatures is of greatest interest to researchers. "We studied what biology can do [in these extreme environments] today and applied it to our understanding of the earth 4 billion years ago," Sheik said. After collecting microbial samples from the mine, they used various growth conditions and DNA sequencing to characterize them in the laboratory. The goal is to better understand the mechanisms and key genes that allow bacteria to grow and replicate in natural environments with scarce resources.
Slow changes and movement speeds in the deep underground environment may also affect microbial evolution. For extremophiles living in the deep sea, it is very common that they have not encountered other organisms for hundreds or even thousands of years. This means that predation, symbiosis and gene transfer rates in these communities are very low. Surviving in a resource-poor environment may also mean slow replication or even long-term aging. These conditions may affect the activation of genes in these extremophiles and the way they change over time. "We don't fully understand how [these microorganisms] eat, reproduce, or evolve," Sheik said. "Advanced genomic tools are helping us understand the evolution and energy flow of these complex communities."
Microbial colonies formed a mixture of orange, yellow and brown in a stream that passed through the tunnel of the former Sudan iron mine. Considering the limitations of the deep mine environment, the researchers found a surprisingly complex microbial community here. Credit: Josh Nakert.
Soudan has presided over a number of large-scale physics experiments, including the Main Injector Neutrino Oscillation Search (MINOS) project. MINOS ended in 2016, and the large neutrino detector placed in this excavation hall of the former mine has been dismantled. Credit: Josh Nakert.
Tullis Onstott, a terrestrial microbiologist in Princeton, studied life in environments deeper than Sudan, collecting microbes from active gold mines in South Africa. The four active gold clusters he works for—the East and West Driefontein mines and the Kloof mine near Carletonville, and the Beatrix mine near Welkom—are among the deepest mining areas in the world, reaching 3.4 kilometers of surface depth. These depths provide more challenging living conditions, including temperature increases due to increased geothermal activity. The pressure at these depths is so great that the boreholes drilled by mining companies will close within a few months; the most significant cracks or fissures formed by gradual rock movement and seismic activity have a similar fate.
Despite the harsh conditions, “we found that very active communities have adapted to their environment,” Onstott said. Single-cell life at a depth of several kilometers once seemed impossible, but in 2011, Onstott and his collaborators discovered tiny worms called nematodes that lived under the extreme conditions of the Beatrix Mine. "We were surprised to find multicellular organisms," he said. "They feed on bacteria." Worms may also have bacterial symbionts, which suggests that the underground food web is more complex than previously assumed. His team also discovered an amazing diversity of viruses underground, adding to the complexity of the potential flow of genes and nutrients between organisms.
Located in the former Homestake gold mine (now SURF) in South Dakota, the Davis experiment was one of the first large-scale underground physics experiments. The experiment used a 380 cubic meter storage tank filled with perchloroethylene to successfully confirm the existence of solar neutrinos and provided evidence that neutrinos have three "flavors"-this result was later used by the project leader Lei Davis won the Nobel Prize. Image credit: Anna Davis, Sanford Underground Research Institute, ©South Dakota Science and Technology Authority.
The unexpected diversity and complexity of life deep underground provides researchers with a range of opportunities to ask key questions about the origin of life on this planet and other planets, such as how the genetic building blocks shared by all life are formed and how cells are obtained The ability to generate energy through breathing. Researchers are still studying whether it is possible for multiple forms of life on Earth to evolve at the same time — so if one early gene form outperforms others — and what life on Mars might look like if it did evolve.
While biologists are exploring the origin of life, physicists are using underground research facilities to ask questions about the origin of the universe. After discovering that a thick layer of rock blocked most of the cosmic radiation from the sun and other celestial bodies continuously falling on the earth, they were attracted to the ground by the radioactive silence.
This radioactive quietness allows extremely sensitive detectors to record the trajectories of subatomic particles called neutrinos, which are produced by the decay of radioactive elements in the sun and distant high-energy events such as supernovae, black holes, and gamma-ray bursts. Since particles are not affected by magnetism because they have no electric charge, and because they can usually pass through matter unhindered, they travel in the universe along a straight trajectory at a speed close to the speed of light, basically unchanged. However, in rare cases, when a neutrino collides with an atomic nucleus, the collision will produce a rapid flash that can be detected by the detector. Therefore, physicists treat neutrinos as messenger particles directly from any high-energy event that produces them, and use these particles to learn more about the sources of the universe and other aspects that we know little about, such as the relationship between matter and antimatter. The balance and the universe.
Neutrino research is one of the main objectives of the Sanford Underground Research Facility (SURF) in SD Ryder, which is the deepest research facility in the United States at a depth of approximately 1.5 kilometers. The laboratory is located in the former Homestake gold mine, where gold was mined from 1876 to 2002, after which it was transformed into a specialized research facility. However, the mine’s physical experiments have a long history, beginning with the Davis experiment in the mid-1960s. Under the leadership of Brookhaven National Laboratory physicist Ray Davis, researchers tried to confirm that the sun emits neutrinos. He won the Nobel Prize in 2002 for this work. The instrument built by the Davis team at SURF did detect solar neutrinos, but strangely, only one third of the predicted rate. As confirmed by subsequent experiments, this is not a case of inaccurate detectors, but one of the first signs of three types or tastes of neutrinos: electron neutrinos, the type observed by the SURF detector, and mesons and tau neutrino.
A catalogue of historical core samples and information from the ancient Homestake gold mine helped SURF engineers and scientists better understand the physical characteristics of local rocks, saving time and money when conducting contemporary excavations there. The derrick of the Yates shaft opened in 1938 (as shown in the picture) is the main channel for personnel and equipment to enter deep underground. Image credit: Matthew Kapust, Sanford Underground Research Institute, ©South Dakota Science and Technology Authority.
The construction of the next generation detector broke ground at SURF in 2017. The construction of the new detector takes ten years and is part of a large-scale international research cooperation project called "Deep Underground Neutrino Experiment (DUNE)", which brings together more than 160 experiments from 30 countries/regions About 1,000 scientists in the laboratory. In addition to the SURF detector, another major part of DUNE is the source of neutrinos, which is the particle accelerator of the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. The accelerator will send a concentrated beam of neutrinos through the earth to the SURF detector about 1,300 kilometers away, where only a small number of primitive neutrinos are expected to be detected. Researchers are interested in how these neutrinos scatter and change after interacting with other subatomic particles during underground travel. SURF's detectors will also be able to observe high-energy neutrinos coming through the earth from cosmic sources such as supernovae.
"Based on current restrictions, DUNE is designed to have the greatest sensitivity," said Jonathan Paley, associate scientist at Fermilab. SURF's high-resolution detector is the largest of its kind, and "can observe three-dimensional neutrino interaction events with unprecedented resolution," Paley said. This level of detail will help DUNE cooperate to obtain as much information as possible from these messenger particles, including their energy, taste, and possibly their incoming direction, as well as other characteristics. The more researchers can determine the characteristics of a given neutrino, the better they can understand its source and the strong physical events that produced it. The neutrino researchers participating in DUNE hope to answer the unresolved questions about the balance of matter and antimatter, the stability of matter, and the universe that occurs within supernovae, and expand our understanding of the basic physics of the universe, revealing processes that we have not yet discovered. Not yet observed.
In general, Operation Ningci has proved to be a great boon for underground research work. In the study of deep-dwelling microorganisms, Onstott said that as mining operations continue to expose new surfaces through drilling and blasting, he is happy to be able to reach uncontaminated parts of the rock. Fresh exposure can sometimes expose organisms to organisms that have only recently been exposed to oxygen, and these organisms may have been undisturbed for tens of thousands of years. However, for scientists working in active mines, ongoing operations can also be a hassle. The mine owner decides when and where to conduct the research; the same blast exposing fresh rock also limits the time researchers spend in the mine. "Everything has to be planned in advance, and we have to run a lot of time. We want to [sampling and placing collection equipment] as much as possible before clearing the mine at the end of the day for blasting," Onstott said.
However, this is not a problem of decommissioned mines. At the Homestake mine where SURF is located, “there are no competing interests, research is everything,” said Constance Walter, SURF’s communications director.
The DUNE project under construction involves four large detectors 1.5 kilometers below the surface of SURF. These detectors will study the neutrinos produced by the accelerator at Fermi National Accelerator Laboratory in Illinois, about 1,300 kilometers away. The current timetable calls for two of these detectors to be online by 2026. Credit: Fermilab.
Past mining work can tell researchers a lot about the physical characteristics of the rocks around the mine, how the rocks were formed, past seismic activity in the area, and other useful information. "Homestake Mining Company has done an excellent job of cataloging rocks," Walter said. "We are fortunate to still have their core samples with a long history." Researchers working in Soudan also benefited in the same way, inheriting the historical core samples after the mine was taken over by the state. Compared with drilling new holes or digging from scratch, being able to use these past records can save a lot of time and money. As part of the SURF collaboration, William Roggenthen, a geological engineer at the South Dakota School of Mines and Technology, studied the mechanical properties and behavior of soil and rock. This work is related to understanding the expected behavior of materials in applications related to construction, mining, dams, and geothermal development, and the development of new materials. It is often difficult to economically justify such research on deep natural rock formations. But at SURF, he “can get close to the rock mass I want to investigate in a cost-effective way,” Roggenthen said.
Before SURF built the DUNE detector, approximately 875,000 tons of rock had to be removed, which required detailed planning, test excavations (as shown in the picture), and careful execution. Image source: Sanford Underground Research Facility, © South Dakota Bureau of Science and Technology.
But sometimes, once the mine is turned into a research facility, further excavation is required. For example, at SURF, engineers still have to dig a small warehouse-sized rock more than 1 kilometer underground to install the large detectors required by DUNE. To accomplish these feats, the underground research facility has brought in civil engineers, including many people who usually dig tunnels for roads and subways.
David Vardiman, the geotechnical engineer responsible for the SURF excavation, said: “Typical mining excavations value the volume of moving rock and don’t care about the quality of the walls or the long-term stability of large caves.” The process of creating these research facilities requires greater precision. Especially in blasting mode. The rock walls have been carefully polished and stabilized with cables and concrete. The final product looks more like an airplane hangar than a cave. While the building is different from a typical mining agreement, it is important to understand the history of the mine. The 140-year history of excavation at the Homestake mine provides “a better understanding of how the rock mass responds to excavation,” Vardiman said. The historical core also helps engineers choose the old Homestake mine that is most suitable for large-scale excavation in the area. This kind of engineering and attention to detail leads to huge underground spaces that can take decades.
The neutrino sensing DUNE detectors will each hold 70,000 tons of liquid argon. Credit: Fermilab.
Given their unorthodox environment and their participation in answering basic scientific questions, many underground experiments have caused a lot of sensation. This attention provides some staying power for these projects, many of which are larger projects planned to run for decades. "DUNE is a very exciting project," Paley said. "It provides a broad research plan covering many key topics, which will keep us busy for a long time."
In addition to researchers studying the origin of life and particle physics, researchers in many fields are using the unique accessibility of the underground environment to conduct various investigations. Computer hardware companies have placed hard drives underground to assess whether cosmic rays will damage data storage; seismologists have installed geophysical arrays that are sensitive enough to detect the ripples of tsunami waves that reach the west coast of the United States from as far as the Indian Ocean; Microbiologists isolate bacteria from decaying mine wood. These bacteria help produce more efficient biofuels. The isolation that draws researchers underground also provides an attractive trap for things that need to be placed for a long time, such as radioactive waste or carbon captured from power plants or the atmosphere.
SURF has a visitor center full of exhibits to maintain public support for underground research facilities, most of which are at least partially supported by public funds. Image source: Matthew Kapust, Sanford Underground Research Institute, ©South Dakota Science and Technical Bureau.
Despite the great potential of underground research, the facilities that carry this type of work still face ongoing challenges. As with almost all research, funding is the biggest unknown. Researchers working in active mines often rely on the profitability of the mine. The maintenance cost of deep excavation is very high. If the pumping system is not maintained, landmines will slowly fill up with groundwater. For example, between the time the Homestake mine was completely decommissioned in 2003 and became a full-time research facility in 2007, the mine slowly filled with water. Before construction of the research space begins, the mine must be evacuated and refurbished.
Coupled with other necessities, such as circulating fresh air, regular safety inspections, and operating mine cages, the cost of a single mine can easily reach hundreds of thousands of dollars a year. "South African mines are beginning to close [due to declining profitability], which means that we will eventually be unable to enter," Onstott pointed out.
Soudan and SURF each rely on a mix of public and private funds, but these sources are also limited and volatile. Sudan as a state park relies heavily on state funding, which means that budget cuts or fewer tourists may close the mine and mean the end of research there. SURF was established by a private donation of US$70 million from T. Denny Sanford and US$40 million from South Dakota, but it continues to receive funding from the National Science Foundation and the Department of Energy.
Promoting cooperation and highlighting the return on investment is the key to maintaining public support for these facilities, and those involved in their operations often reiterate this. As part of the donation, Sanford asked SURF to promote education and outreach. The instruction is achieved through visitor centers that provide detailed information to guests, internships, scholarships, student group activities, and collaborations with several nearby universities that support various local jobs. Dedicated educators and outreach personnel have also developed curriculum packages and sent them to classrooms in South Dakota and other regions. These toolkits are "particularly popular because they give teachers... the opportunity to incorporate practical, inquiry-based science units into their classrooms," Walter said, noting that other national and international laboratories have contacted SURF Seek help to develop their own educational curriculum plan.
Underground research facilities can not only conduct particle physics and microbiological experiments, but also conduct scientific research. For example, at SURF, researchers have begun to study rock mechanics and geothermal systems as part of the stimulus investigation of geothermal modeling and analysis projects. The project involved drilling multiple boreholes to inject and produce geothermal water, as well as monitoring. Image source: Sanford Underground Research Facility, © South Dakota Bureau of Science and Technology.
In Soudan, Sheik, Brengman and the retired miners who are still working, visiting and operating the museum hope that enough tourists will visit the mine to keep it running, perhaps because of curiosity about the 800-meter fascinating iron-rich rock The heart is attracted by the opportunity to have lunch below the surface or sitting on a box marked "TNT/Explosives" and having lunch in a historic mining operation. They also hope that more researchers will realize the benefits of working underground-the underlying science conducted there is as exciting as the underground environment itself.
"These are unique environments for asking important questions," Onstott said. "What always kills us is the lack of access rights," and there is never a lack of new problems.
© 2008-2021. all rights reserved. It is strictly forbidden to copy, redistribute, or retransmit any content of this service without the express written permission of the American Institute of Geosciences. Click here for all copyright requests.