Sarah Johnson was just interviewed by David Baron for the Library of Congress Podcast, Space on the Page.
Full Description from the Podcast:
"The hunt for life on Mars has entered a new phase. NASA’s Perseverance Rover is collecting rock samples that, when returned to Earth, may reveal whether life once existed on the red planet (and perhaps still does). Biologist Sarah Stewart Johnson explains how new discoveries about Mars and a better understanding of life on Earth have propelled this quest, and she ponders what the answers might say about life elsewhere in the universe. Johnson is author of “The Sirens of Mars: Searching for Life on Another World.”"