South Dakota’s Wind Cave seen under normal white light transforms into something otherworldly when ... More
When exposed to ultraviolet light, some minerals glow, a phenomenon known as fluorescence. Scientists are studying these fluorescent minerals to better understand the conditions that support life in caves, research that could offer insights into how life might survive on other worlds.
The findings were presented at the American Chemical Society spring meeting, which took place recently in San Diego.
The cold and dark conditions found in South Dakota’s Wind Cave and other caves across the U.S. share some similarities with potential extraterrestrial environments, like caves beneath the surface of Mars or sub-glacial water bodies on the icy moons of Saturn and Jupiter. This has led astrobiologist Joshua Sebree, a professor at the University of Northern Iowa, to venture deep underground to study the minerals and life forms thriving there.
“The purpose of this project as a whole is to try to better understand the chemistry taking place underground that’s telling us about how life can be supported,” he explains.
Typically, to understand the chemical makeup of a rock formation a rock sample is removed and taken back to the lab. But this procedure causes permanent damage and can alter the very ecosystem the scientists want to study. Sebree and his students developed a non-invasive approach, collecting the fluorescence spectra of cave sections.
Under ultraviolet light, certain areas of the cave transform into something otherworldly. Thanks to impurities lodged within minerals, the rocks start to glow in vivid shades of pink, blue, yellow and green.
“The walls just looked completely blank and devoid of anything interesting,” says Sebree. “But then, when we turned on the black lights, what used to be just a plain brown wall turned into a bright layer of fluorescent mineral that indicated where a pool of water used to be 10,000 or 20,000 years ago.”
The colors correspond to different concentrations and types of organic or inorganic compounds. Organic molecules derive from the fossilized remains of microorganisms once living on the rocky surface, inorganic molecules were deposited by liquid water dripping down the cave’s walls.
The team is now working on a database to match the colors and their intensity to specific components and how they sustain life. They are also working on an automated spectrometer — an instrument used to separate and measure spectral components of light and other radiations — that could be installed on a planetary rover and search autonomously for signs of life.
Additional material and interviews provided by the American Chemical Society.