Fluorescent Caves in the US Offer Clues to Potential Extraterrestrial Life on Europa

Researchers are exploring caves in the US, including Wind Cave in South Dakota, where they've discovered that under UV light, the cave walls transform into luminous displays of green, blue, and pink fluorescent minerals. According to a team at the University of Northern Iowa led by Professor Joshua Sebree, these minerals, deposited by water thousands of years ago, could potentially support life in extreme environments, similar to those found on Jupiter's moon Europa. The goal is to use the fluorescent features to understand how the caves formed and how life is supported in extreme environments, but the data may also reveal how life could persist underground on worlds such as on Jupiter's icy moon Europa. The team explained that the chemistry in the cave is likely similar to places such as Europa. A portable instrument was used to analyze the light emitted by the rocks, identifying the minerals without altering the cave. Sebree's team circumvented the typical process of collecting physical samples for laboratory analysis by recording fluorescence spectra with a portable spectrometer. The spectra for each mineral are like a unique fingerprint, allowing the team to identify the compounds present without damaging the cave system. Sebree says that, under the black light, certain areas of the caves seemed to transform into something otherworldly as portions of the surrounding rocks shone in different colors thanks to impurities lodged within the Earth millions of years ago. The hues corresponded with different concentrations and types of organic or inorganic compounds. The team found that manganese-rich waters had carved out the cave and produced the striped zebra calcites within, which glowed pink under black light. Sebree believes that when the rocks shattered, since calcite is weaker than the limestone also comprising the cave, the calcite worked to expand the cave too.