Cosmic rays and underground science: taking biology deep underground

By Blaire Flynn

Each November researchers connect with high school students around the world to work together learning about cosmic ray particles during International Cosmic Day. This global science outreach initiative, now in its 13th year, provides the opportunity for students to collaborate like scientists and learn about cosmic ray particles that are constantly whizzing by, and through, us continuously! If you held your hand out on the Earth’s surface, approximately every second a cosmic ray particle would pass through it. 

While cosmic rays are fascinating, high-energy particles studied by a variety of experiments, those that are looking for rare particle interactions would be overwhelmed by cosmic rays if they were located on the surface of the Earth. This is why some particle physics labs, including SNOLAB, are located deep underground. For SNOLAB, the 2 kilometers of rock overhead provides a reduction in cosmic rays by a factor of 50 million as compared to conditions on the Earth’s surface. This means if you held your hand out underground at SNOLAB, it would take a couple of months before a cosmic ray passed through – a massive reduction from a rate of one every second on surface. This reduction in cosmic rays allows the experiments at SNOLAB to observe more elusive particles, like neutrinos and dark matter candidate particles. 

The unique environment of SNOLAB allows for more than just large-scale physics experiments. There are biology experiments that benefit from extremely low levels of cosmic radiation. REPAIR is a biology experiment currently underway in the Life Sciences Laboratory at SNOLAB. “We’re looking at what happens when we take away the natural ionizing radiation that is present on the Earth’s surface,” says Dr. Michel Lapointe, a postdoctoral fellow with the REPAIR project at SNOLAB. The project is jointly run by Laurentian University and NOSM University and the acronym REPAIR stands for “Researching the Effects of the Presence and Absence of Ionizing Radiation”. As their name suggests, the team is investigating the effects that cosmic radiation has on biological systems. 

Life on the Earth’s surface has evolved in the presence of background radiation and cells have highly efficient mechanisms in place that repair the damage that ionizing radiation causes to DNA. Since cosmic rays are the major source of ionizing radiation on surface, they bring their experiment deep underground to SNOLAB. Here they have a further reduced space that gives them a radon free environment providing three distinct groups to compare data from; regular cosmic radiation on the Earth’s surface, the ultra-low radiation conditions at SNOLAB, and their radon free glovebox.   

To date the REPAIR project has run experiments on five different biological systems and their results seem to indicate that while exposure to too much radiation is not good for cellular growth and development, removing all the ionizing radiation is not good either. “Recently we found that when we take away all of the naturally occurring radiation from cells, they appear to turn into cancer more often”, explained Lapointe. 

Currently, the REAIR team is working on an experimental run using liquid cultures of yeast cells that will allow them to observe multiple generations of yeast growth. Lapointe explained that, “previous studies using other model organisms, especially microbes, have found that prolonged exposure to sub-natural background radiation environments tends to decrease the growth rate and the doubling time of those microbes.” Members of their team are underground at SNOLAB three times a week to work on their experiment and take data on the hour during their shifts to understand how the removal of cosmic rays is impacting the growth rates of yeast cells. Once the experimental run on the liquid yeast cultures is complete, the group aims to run more studies on human cell lines.  

The REPAIR Collaboration is part of a small but active global community of researchers working in deep underground environments to learn more about how the reduction and removal of ionizing radiation, like cosmic ray particles, impacts cellular development. This work could provide important data for informing rates of ionizing radiation that are safe for human exposure.