New Research on Microbes Expands Known Limits for Life on Earth and Beyond
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New research led by Stanford University scientists predicts life can persist in extremely salty environments, beyond the limit previously thought possible.
The study, published Dec. 22 in Science Advances, is based on analysis of metabolic activity in thousands of individual cells found in brines from industrial ponds on the coast of Southern California, where water is evaporated from seawater to harvest salt. The results expand our understanding of the potential habitable space throughout our solar system, and of the possible consequences of some earthly aquatic habitats becoming saltier as a result of drought and water diversion.
"We can't look everywhere, so we have to be really deliberate about where and how we try to find life on other planets," said senior study author Anne Dekas, an assistant professor of Earth system science in the Stanford Doerr School of Sustainability. "Having as much information as we can about where and how life survives in extreme environments on Earth allows us to prioritize targets for life-detection missions elsewhere, and increases our chances of success."
Scientists interested in detecting life beyond Earth have long studied salty environments knowing that liquid water is necessary for life, and salt allows water to remain liquid at a wider range of temperatures. Salt can also preserve signs of life, like pickles in brine. "We think that salty places are good candidates for finding signs of past or present life," said lead study author Emily Paris, a Ph.D. student in Earth system science who is part of the Dekas Lab. "Salt could be the very thing that makes another planet habitable, even though it's also an inhibitor to life in high concentrations on Earth."
The new research is part of a large collaboration called Oceans Across Space and Time led by Cornell University professor Britney Schmidt and funded by NASA's Astrobiology Program, which brings together microbiologists, geochemists, and planetary scientists. Their goal: to understand how ocean worlds and life co-evolve to produce detectable signs of life, past or present. Understanding the conditions that make an ocean world habitable, and developing better ways to detect signals of biological activity, are steps toward predicting where life could be found elsewhere in the solar system.