Dr. Cassandra Marnocha Explores Motility as a Key Biosignature for Extraterrestrial Life

In the search for extraterrestrial life in the universe, biosignatures, which indicate or suggest the presence of a biological process indicative of life, are critical determinants. However, much of what we know about biosignatures is informed by our current understanding of life on Earth.

For the next two years, Dr. Cassandra Marnocha, associate professor of biology and director of environmental sciences at Niagara University, will be working as part of a collaborative team with colleagues from Johns Hopkins, Purdue, and the SETI Institute, as well as student researchers from her lab, to evaluate if motion by life can be distinguished from non-living motion to determine whether motility can be considered an agnostic biosignature.

The work is supported by a $338,420 grant from NASA, awarded to Dr. Marnocha and her research team following a NASA Ideas Lab on biosignatures in February. During the six-day workshop, which was held both in-person and virtually, participants from a diverse range of disciplines gathered to produce radically innovative research proposals to address the challenges presented by the use of biosignatures to determine life. Dr. Marnocha's was one of only six selected from more than 20 projects proposed.

"The past search for life on other worlds has really been focused on finding stuff that is Earth-like, because that's the only life that we know," Dr. Marnocha explained. "But the agnostic biosignature says it should be something more universal, something that doesn't have to be based on Earth biochemistry."

Starting with the premise that cell movement is a feature in all groups of life, Dr. Marnocha and her colleagues began to consider what actually distinguishes living motility from non-living movement, such as Brownian motion, wind, evaporation, freezing, and acceleration due to gravity. Using a combination of time-lapse light microscopy, image analysis algorithms, and a comprehensive validation framework, their work aims to determine if biotic movement can be categorized as a biochemistry-independent, agnostic biosignature.

"Currently, biosignature research is largely based on detecting the biochemistry of life as we know it," she said. "In the case that life elsewhere in the solar system evolved completely different biochemistries, it is necessary to develop new and novel methods to detect it. Our proposal is transformative, as we are developing a composition-independent biosignature that is based on how life moves and interacts with its environment."

Dr. Marnocha and her students will collect a diverse suite of time lapse microscopy images, including movements such as cell displacement, growth, reproduction, and cell-cell and cell-environment interactions, that will be used to develop an algorithm that may identify and classify particular movements as markers of life or nonlife.

This work will be the most expansive study of movement as a biosignature to date and one of the few to study a truly agnostic biosignature, Dr. Marnocha noted. Even if their research determines that living movement and growth cannot in all cases be distinguished from non-living movement and growth, the work is still significant, as it will help to understand which types of samples or cases of movement and growth may be distinguishable as living and warrant further study, and which are ambiguous and do not show promise for further investigation.

"NASA is very careful about biosignature development, because if you are saying we found life on another world, that's an extraordinary claim, and that requires extraordinary evidence," she said.

Dr. Marnocha, who holds a Ph.D. in planetary science, is especially excited about this opportunity because it enables her to refocus on her interest in astrobiology.

"I think one of the really big questions that humanity has is 'Are we alone?'" she said. "And that's what's always fascinated me about astrobiology. It's a huge question, and no one single person is going to answer it, but it's really exciting to be a part of the actual practical approach to answering this question."