by Katy Swordfisk
April 23rd 2025
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Researchers collect samples from Mount St. Helens to analyze for life signs using digital holographic microscopy.
New research from Portland State University successfully identified signs of life in extreme environments on Earth using a technique that could be used to search for life on other planets.
"These environments are considered analogs for extraterrestrial settings, such as those found on other planets and moons in our solar system," said Carl Snyder, lead author and Ph.D. candidate in physics at Portland State.
Researchers looked for three types of lifesigns (also known as biosignatures): active motion (i.e. swimming), morphology and optical properties. They used an advanced microscope in a range of extreme environments — many of which had not been previously explored with this technique.
Carl Snyder gathers samples for testing on Mount St. Helens.
Snyder and his coauthors found that swimming was present in every environment tested, ranging from hot deserts to Arctic ice and alkaline springs. This supports the idea that some fraction of microbes have the ability to swim that is detectable even in extreme environments. The morphology and optical properties indicating microbial life were detected in almost all environments.
“These biosignatures are present almost everywhere on Earth, and therefore, if life has evolved somewhere else, they likely have these biosignatures as well,” he said. “If you go looking for life out in the solar system, we think these are good biosignatures to look for because we see them everywhere on Earth.”
Researchers gather ice samples from caves on Mount St. Helens.
The research also highlights digital holographic microscopy (DHM) as a promising tool able to analyze liquid samples for signs of life as part of future space missions. To explore this further, researchers introduced chemical and thermal stimuli to test their effects on microbial motility. The responses varied — some environments showed strong microbial reactions, while others showed little to none. Despite these differences, a consistent finding across all sites was the presence of microbial biosignatures identifiable with DHM.
“There are ways to use this technique not just in spaces that have liquid water or ice samples, but potentially exploring caves in Mars where it’s mostly a dry surface,” Snyder said. “Or Titan, one of the moons of Jupiter, has liquid methane oceans. That life is going to look very different from ours, but there’s liquid so this instrument could be useful there too.”
The implications of Snyder’s work could drive the human desire for knowledge about life in the universe. But what he finds most interesting is the potential for understanding about how other life functions in ways differently than life on Earth.
“Life teaches us so much about how to adapt and build our own set of tools. We use nature all the time to develop,” Snyder said. “I think there would be a lot of new things that we can learn and practically apply to our everyday life.”