In the deepest mine in Britain, Cleveland Potash Ltd are extracting the salt that keeps our roads safe in winter, and potash to fertilise our fields. It’s a 6 minute trip down in the lift, to the tunnels 1.1 km below the surface. But not all of the staff wearing luminous orange overalls and protective helmets are miners – some of them are scientists. Boulby Mine is also home to the only deep underground science facility in the UK.
When scientists first arrived at Boulby, in the 1990s, their lab was little more than a garden shed. Next came a dedicated facility, the Palmer Lab, operated as a clean room, and with air-conditioning to temper the stifling heat underground. After over a decade of occupancy, the Palmer Lab is reaching the end of its operating life. The building is suffering from movement of surrounding rock due to a nearby fault line, and will soon be removed. In 2014 STFC gave £1.77M in funding for the construction of a new laboratory underground, which will be finished and ready for action in late summer 2015.
Boulby is a special place for science, the deep underground environs enabling a diverse range of studies from astro/particle physics to studies of geology, geophysics, climate, the environment, life on Earth and beyond. You can learn more about the facility via its web page, Twitter and Facebook.
Much of the early work conducted at Boulby focused on the search for Dark Matter. The depth of the mine offers a 1 million factor in shielding from interference from cosmic rays, and the surrounding salt itself is very pure and doesn’t emit much in the way of radiation. All of this is very important when you’re looking for WIMPs, the Weakly Interacting Massive Particles that are thought to make up Dark Matter, the ‘missing matter’ in the Universe.
Based on observations such as the amount that light from the distant galaxies is bent before it reaches us (known as gravitational lensing), and the rate of spin of galaxies, astronomers believe that we can only see around 5% of the ‘stuff’ that makes up the Universe. The rest is dark matter and dark energy, invisible to us.
WIMPs rarely interact with the matter that we can see, and so scientists have built a range of ever more sensitive particle detectors to try and catch some of them and prove their existence. Sensitive detectors need to be kept away from cosmic rays and everyday background radiation that would bombard them with particles and mask any signal from WIMPs – and Boulby is an ideal location for them.
So far neither the detectors operating at Boulby, nor those operating in the few other deep underground laboratories around the world, have made of positive detection of WIMPs. But the search goes on. Professor Sean Paling, director of the Boulby Deep Underground Facility, believes that the next generation of detectors could find WIMPs in the next five years.
Particle physics isn’t the only science going on at Boulby. The unique qualities of the location mean that the team can use it to make extremely accurate measurements of the radioactive emissions of materials – an important factor to take into account when you’re deciding what to build your next dark matter particle detector from. Materials are screened here to be incorporated into dark matter detectors in the UK and elsewhere in the world. The screening facility is also useful for sample radioactivity measurements important to industry, and for ultra-high sensitivity radio-dating measurements important in various environment, climate and archaeological studies.
Another project is underway to place muon detectors at various locations in the mine to explore a potentially very important new a way of imaging large geological structures overhead. The technique, called muon tomography, is a geological equivalent of medical X-ray imaging, and an alternative to seismic surveys. Funded by Premier Oil, this technology is of interest in a number of areas including containment monitoring in carbon capture and storage sites, where we could lock away excess carbon dioxide from the atmosphere to help alleviate climate change.
The mine tunnels extend over 1000 kilometres underground, with 40 kilometres being dug every year. As Boulby is on the coast, some of those tunnels are under the sea. An early demonstrator for this project will involve a muon detector placed in one of those submarine tunnels, to show the technique is capable of tracking the tiny overburden changes due to the ebb and flow of the tides many hundreds of metres above.
Boulby Underground Laboratory & BISAL
(Credit: BBC News)
The wider mine also provides the perfect environment for a wide range of science, from geology and environmental studies through to the search for life in extreme environments. Microbes can be found living in salty puddles within the mine, and studies of these can help us understand more about the existence and survival of life – not only on our planet, but elsewhere in the solar system as Mars and Europa have similarly salty environments that could be home to alien life. The caverns at Boulby Mine are now being used as a ‘Mars analogue’ site, suitable for testing equipment and technologies that could one day be sent on a mission to the red planet.
The Boulby mine owners and other mining companies are also interested in this work, as instrumentation developed for extra-terrestrial exploration may also have significant benefit in commercial mineral exploration and extraction on Earth. This science-meets-industry work is being progressed though in a series of working meetings as Boulby attended by a number of instrumentation development teams from a range of UK and international research institutions including NASA and ESA.
Boulby’s new lab will be home to these research programmes, and many more, over the coming decade. It has indoor facilities for clean rooms and particle detectors, as well as ‘outdoor’ areas for access to the mine tunnels. The one thing that won’t change? Scientists will still need to wear those orange jumpsuits on their way down.