Explainer: Potential explosives found at Antarctic explorer laboratories

Representatives from New Zealand have warned about the possible presence of picric acid crystals, picric acid solution and peroxide crystals in Antarctic huts used by the 20th century explorers Ernest Shackleton and Robert Scott. These chemicals are highly sensitive to disturbances and, if their existence is confirmed at the sites, will need to be disposed of carefully. But why would these potentially explosive chemicals be in Antarctica in the first place, and how big is the risk?