Robert J. Nemiroff Professor (Physics): Michigan Technological University   Co-Founder & PI: Astronomy Picture of the Day (APOD: apod.nasa.gov) Co-Founder: Astrophysics Source Library (ASCL: ascl.net) Organizational Lead: 75th & 100th Anniversary Astronomical Debates Author: Journals: Over 75 refereed science publications

How will humanity first discover ET Life?Best guess*: Biosignatures (Solar System: Mars) The search for biosignatures on Mars is the most comprehensive Future missions will continue to study Mars in unprecedented detail Planned missions include: NASA’s Mars 2020 (w/ Perseverance rover) China’s Tianwen-1 ESA’s ExoMars 2022 (w/ Rosalind Franklin rover) Past ambiguous signs of Martian life could be verified by new data Methane variations Surface chemical anomalies   Therefore: “first discovered life” could actually predate 2020 * This area is outside of my research specialties

How will humanity first discover ET Life?Life is detectable all over Earth’s surface with the exception of small desert areas (see, for example, Navarro-Gonzalez 2003) By contrast, life -- or fossils of past life -- may be detectable only on small areas on Mars, with most of the present Martian surface being a desert Extremophile Earth microbes might be able to survive under the Martian surface Martian microbes might not only be DNA or RNA based, but even share a common ancestor with Earth life Life might have been spread through the inner Solar System by meteor strikes (see, for example, Burchell 2004) Humanity has already placed life on Mars Some spacecraft that landed there were “contaminated” with Earth microbes (see, for example, Madhusoodanan 2014)

Humanity should continue to study how to find ET life Where are the bottlenecks in the development of life? What planet or moon environments get around these bottlenecks the best? What are the easiest technosignatures to detect from the relics of long-dead technological societies? Which moons have the most life-enabling underground seas? Where are the best places to land on these moons? What are the least ambiguous biomarkers in exoplanet atmospheres? A Biological Copernican Principle: “Earth life is neither unique nor central”

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