Sarah Stewart Johnson, a planetary scientist at Georgetown University, shares the story of that quest and how the science of searching for life on Mars has progressed in her lyrical new book, "The Sirens of Mars: Searching for Life on Another World" (Crown, 2020).
Space.com talked with Johnson about the search for life on Mars in the past, present and future.
The Sirens of Mars: Searching for Life on Another World.
Sarah Stewart Johnson: The book is about the search for life on Mars, but it's not just the science of it; it's about our human relationship to the planet as well.
Slowly, it just ended up being different things interwoven together, from my personal story and why I found Mars so endlessly fascinating, to the scientists that came before me and all of my predecessors and the lengths that they were willing to go to, to try to figure out if we're alone in the universe.
Johnson: I think something that really struck me was how so many Mars scientists have come from completely different walks of life … Folks came at this from all different backgrounds with all different initial thoughts — people that were really interested in wilderness or people that were really interested in benevolent civilizations.
You sort of see this reflection in some ways of what they most longed for in their theories about Mars, and I just found that very poignant … It was a paring down; there are lots of people and lots of passages that ended up in the graveyard of text that didn't quite make it into the book … .
I had this box filled with things that I would find when I was, in my spare time, thinking about the book — things like old letters or photographs, or scientific articles where you could really see scientists struggling with trying to understand something that is very evident today but wasn't in their historical period?
It's just a refuge almost; it's just weather and it's just vegetation … I think it was something that he most longed for — this world that was free from all of the horrible things that were happening in his world, on his planet.
Johnson: This project has really been percolating for a while … The book, in many ways, just filled pockets of spare time here and there … It seemed like a point where even though we didn't have the data [that the Perseverance rover will gather], that this would be a time where people might be curious about Mars.
It's only every 26 months that the planets swing together on the same side of the sun, and it's a really exciting time for the Mars community with these three missions launching in the next couple of weeks.
Related: The search for life on Mars (a photo timeline).
Johnson: Even the discovery of simple life beyond Earth, I think, really stands to make a tremendous impact.
Especially if we found evidence of a second genesis [a case where life arose independently of life found on Earth, rather than migrating between the two worlds], I just think it'd be as revolutionary as any breakthrough that's been made in terms of thinking about ourselves and our existence.
It's one of the things I tried to capture in the pages of the book, that there are these really deep questions associated with the search.
Johnson: I guess one of the things for me is that when you think about your life on a planetary timescale and in the context of this enormous universe that we're part of, I think it really makes clear just how short our time here is and how important it is to make the very most of it.
Space.com: Do you think it's possible we'll hit the point at which scientists can confidently say there is no life on Mars, and if so what happens next!
Johnson: It's certainly possible there is no life on Mars, that we'll search and search and, like the moon, we can conclude pretty conclusively that that's it.
One of the things that I tried to write about too in the book is just this idea that Mars is our near neighbor.
What I've tried to do with the book is write a bit of a natural history of Mars, and I do think that the big question — is there life there, is there not — will have a big impact on how we think of the planet, and also how we move through the coming decades in terms of exploration …
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