“The Search for Life on Mars and Beyond,” presented by Carol Cleland, Ph.D., and Sarah Johnson, Ph.D., focused on the ways we find evidence for and classify life on other planets. The lecture was presented by the Science, Technology, Ethics and Society (STES) center as part of its Science Matters lecture series on Wednesday, Feb. 24. After opening remarks by the STES center’s director, Kristen Intemann, Ph.D., Cleland revealed the flaws in our current approach to classifying life. Johnson then proceeded to give an in-depth analysis of our current methods of discovering life. The presentation finished with a Q&A session with the professors. 

Cleland is a professor of philosophy at the University of Colorado, where she researches the Philosophy of Science and the Philosophy of Logic and Metaphysics. She has authored “The Quest for a Universal Theory of Life: Searching for life as we don’t know it” and was a co-author of “The Nature of Life: Classical and Contemporary Perspectives from Philosophy and Science.” 

Cleland’s talk focused on the difference between the definitional approach and the tentative approach to “life.” The definitive approach follows strict criteria for classifying life while the tentative approach is more flexible and includes potential biological anomalies. A large critique Cleland had of The definitive approach was that it encouraged an Earth-centric view on life. This distinction is important as the search for life on Mars deals mainly with analyzing microbial organisms. “No one expects to see little green men and women running around!” Cleland said.

To highlight the flaws of the definitive approach, Cleland brought up the Viking Labeled Release Experiment of 1976. The two principal investigators of the experiment, Levin and Straat, concluded the experiment had shown there was microbial life in Mars’ soil. However, NASA concluded no life was present because of differences between the microbes found in the experiment and the microbes found on Earth. 

Johnson is an associate professor of biology at Georgetown University, where she oversees the Johnson Biosignatures Lab. Johnson’s lab seeks to understand and preserve biosignatures in other planet’s environments. Johnson’s recent book, “The Siren of Mars” was a New York Times Editor’s Choice.

Johnson’s talk was focused on finding life as we don’t know it. As we move further away from Earth’s atmosphere, any life we find is unlikely to share a common ancestor with the life on this planet. This makes knowing what to look for difficult. “It’s like trying to imagine a color you’ve never seen before,” Johnson said. To find and understand these alien microbes, Johnson uses developed analytical tools to find biosignatures on Mars. These specialized skills have been tested on Earth’s most barren environments, such as Antarctica, as well as the early rock record of our planet. Johnson showed four of the tools that scientists use to search for molecular life, pathway complexity, molecular complementarity, chemical fractionation and disequilibrium and energy transfer.

A recording of the lecture can be found at http://www.montana.edu/stes/news/sciencematters/lifeonmars.html.