Scientists have identified signs of the presence of life about 1,300 feet below ground in a massive cave in Italy, an advance that may help detect life on other planets.
Researchers from the Pennsylvania State University in the US explored the microbiology and geochemistry of the Frasassi Caves in central Italy.
They found variations in the isotopic content of atoms in the mineral gypsum, which is a weathering product of the cave's formation.
Not all gypsum is formed by microbes, but gypsum formed by microbes will have a different ratio of isotopes in the atoms, according to the study published in the journal Astrobiology.
This isotopic variation, in combination with other data, indicates that life played an active role in producing the gypsum.
"Using this cave environment, we provide a real-life field example of how we can detect life, past or present, on other planets," said Jenn Macalady, associate professor at Pennsylvania State University.
Scientists know microbes, or microorganisms, speed up chemical reactions. For example, minerals like the gypsum found in the cave form much more quickly in the presence of microbes.
The team collected samples of gypsum from the cave walls that were likely to have come in contact with fluids or moving air and used a mass spectrometer to study the isotopic ratio of the gypsum.
Because microbes speed up chemical changes, Macalady said the presence of isotopic biosignatures could be used to spot the involvement of life forms in forming other minerals, not just those appearing in the Frasassi Caves.
The structure of the Frasassi Caves - teeming with life at the lowest level of the cave and only remnants of life present at varying elevations above - offers a real-world laboratory setting for identifying current and remnant biosignatures.
Mars has caves formed by volcanic activity, which offers a hospitable underground environment for microbes to cling to. Mars also has fluids like carbon dioxide and water, researchers said.
Those fluids could allow microbes to interact with minerals, speeding up chemical reactions like what was found in the Frasassi Caves, they said.
"If we were to find a similar environment on Mars, we could use this particular biosignature to test for the current or past presence of life," Macalady said.
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