A Smithsonian scientist’s lifelong search for evidence that life could have existed on Mars

On March 24, 2015, after 11 years and two months on the Martian surface, the Opportunity rover reached a milestone. On that date, beaten up and partially broken from years of wear and tear, the little rover that could reached a total travel distance of 26.2 miles—the length of a marathon. Technicians at the Jet Propulsion Laboratory (JPL), where they operated the rover, celebrated by running a race. They also named a valley that Opportunity explored extensively in its final years "Marathon Valley" in its honor. 

Opportunity sent troves of data back to Earth for scientists around the world to analyze in hopes of learning more about the red planet’s geology and atmosphere, past and present. One of those scientists was John Grant, a planetary geologist at the National Air and Space Museum. His goal? To find evidence of conditions that could have supported life on Mars.

“It seems that all the necessary pieces are there on Mars for life to have existed,” John told Eye on Science. “We’ve found that there are areas on Mars where water was flowing in the distant past as well as relatively more recently. That’s evolved my thinking from ‘okay, so there was some water long ago' to ‘there were some big lakes there’ to ‘there were habitable environments and maybe life'.”

Years later, when it came time to decide where to land Perseverance rover, John co-led the community process for providing scientific input to the NASA team. With his help, NASA chose to place Perseverance in Jezero crater, which was once thought to be flooded with water, making it a possible breeding ground for life millions of years ago.

If anyone is qualified to ask the question of whether Mars once harbored habitable environments, it is John. He’s been working at the National Air and Space Museum’s Center for Earth and Planetary Studies for 23 years, and he’s been hunting for ancient life on Mars even longer than that. Probes in orbit around the planet and rovers on the surface take images of the Martian landscape, and John searches the areas in and around ancient waterbeds for signs of places that once may have been habitable. If a team of scientists one day announce that they’ve discovered decisive evidence of real, organic, breathing, pooping life on Mars, John Grant may be on that team.

John once said in an interview that “space exploration is a hell of a show.” What did he mean by that? That there are surprises around every corner. As John explained, if we were to find evidence of life on Mars, it would surely make some of us start to question our own existence. “It would tell us more about how life evolves. We only have one data point so far, and that’s Earth,” he pointed out. “There’s been this question since humanity first started to ruminate on big ideas about whether we’re alone in the universe. If you only have to go one planet away to find life, boy does that speak volumes about how life may be distributed throughout the universe. To me, that changes how and why we explore in and outside our solar system in the future. It also provides us, as humans, some perspective on our place in the universe.”

If John and his colleagues prove that we’re not so alone in the universe by studying the planet that’s fascinated him his whole life, that would be quite a moment for him and for humankind.

When John was just 16, the Viking landers became the first two probes to successfully land on Mars and return clear data from the surface. The images the landers sent back made John fall in love. He was already a huge science fiction buff; one of his favorite books was The Martian Chronicles by Ray Bradbury. In the book, humans explore Mars and meet indigenous Martians.

“Bradbury’s talk about ancient civilizations on Mars struck a chord with me, and I tried to find and collect any images [from NASA’s Mars missions] as I could,” John told Eye on Science. “There was no internet back then. The only way I could get those images was to explore newsprint.” John would write to the U.S. Government Publishing Office. “For a nominal fee—basically the price of postage—they’d send you these enormous prints.”

The Viking data made it clear to John, even at 16, that water once existed on the surface of Mars. “There was evidence of these large channels on the surface,” he said. John followed his interest in rock formations to school, where he received a degree in geology, studying the coastlines of Rhode Island. He wasn’t planning on becoming a space geologist at first, but his research adviser asked him to help with a project he was working on for NASA, and John never looked back. The skills, he said, were easily transferable, albeit he couldn’t visit the places he was studying and collect rocks by hand.

But, later, the rovers Spirit, Opportunity, and Curiosity, and the InSight lander, gave John his best chance yet of studying Mars rocks. The Curiosity and Perseverance rovers are active on Mars right now in 2024, both drilling into rocks for evidence that Mars was once habitable, and Perseverance is collecting samples that NASA hopes to return to Earth on a future mission. John’s looking forward to having the future opportunity to study these rocks in a laboratory on Earth. But there’s still more we can do, he says. And that includes landing humans on Mars.

In only a dozen years, Opportunity covered a marathon’s distance, but John invites us to consider that feat relative to what could be accomplished by humans if they could make it to the red planet. “You can look at me and I’m not the guy running marathons, but I can walk around and collect rocks over a much larger area in 12 years. Besides, there’s so much competition for the rover’s bandwidth. You can’t always do what you want to do. But if a human was there, an astronaut could say, ‘oh, that rock over there is a different color than this one,’ and they could walk over to it and pick it up and analyze the surrounding landscape much faster and more efficiently.”

In addition, John says, visiting Mars can have implications in other fields. “Medical doctors have a completely different set of rationales. ‘How does the human body respond to radiation?’ for example. I started to appreciate there is a tremendous number of reasons for us to go and do this. If we're ever going to get off the Earth and be an exploring species, Mars is one of the places where we should start.” 
 
But still, we haven’t gotten to the question of “why?” Why go through all this trouble to study space at all, when we’ve got so many problems to solve here on Earth? Eye on Science has a habit of asking this question to every astronomer, astrophysicist, and planetary geologist we come across.

John’s answer: “Sure, there are problems here at home that, given unlimited resources, could probably be addressed. But by exploring things beyond Earth, we inspire people to get interested in and involved in science. Reaching Mars will inspire a lot of people—dare I say a generation—to go and start tackling those problems. I know engineers who started at JPL who now work in all sorts of tech fields—one is designing robotic irrigation systems; another is working on self-driving cars.”

John gave up a position as a tenured professor to join the Smithsonian so he could focus more on his research, but that doesn’t mean he is not interacting with the public. In fact, the opportunity to speak to new people every day about different topics has heightened his interest in science communication. He’s given talks about Mars to numerous audiences and forums, in the museum and across the country. “It’s an opportunity to meet new people and do something different. It’s never the same thing twice,” he said.