NASA's ambitious goal of establishing a sustained human presence on Mars in the 2030s will involve landing a spacecraft on the distant planet without burning up the crew, producing food and breathable air amid an inhospitable environment, even making rocket fuel from the Martian atmosphere to power the journey home.

But one the greatest challenges may involve something that is no more than a nuisance on Earth — microbes.

When humans embark on the 2.5-year mission to the Red Planet, they'll carry all the water they need for the 34-million-mile trip, continually recycling it through pipes, tanks and filters. Anyone with household plumbing knows what happens in that environment over time.

"It starts to get all slimy, like if you don't clean your kitchen sink for a while," said Montana State University researcher Madelyn Mettler, who has spent the past year studying microbes sampled from the International Space Station.

The slime is more than gross — it can cause major problems. A water valve on the space station failed because it clogged with the stuff, and at the end of its 15 years in orbit, the interior of the Russian space station Mir was coated in microbial gunk.

"It can really wreak havoc on the equipment," said Mettler, a doctoral student in the Department of Chemical and Biological Engineering in MSU's Norm Asbjornson College of Engineering.

That's why Mettler and a team of scientists in MSU's Center for Biofilm Engineering have partnered with NASA to explore specialized material coatings and other strategies for preventing microbial buildup in spacecraft water systems. Mettler will present preliminary findings from the study at the CBE's Montana Biofilm Meeting on July 13-15.

Mettler's research currently focuses on whether various coatings can prevent buildup of two microbes — a bacteria and a yeast — that are commonly found on the space station. The microbes grow together cooperatively to form a slimy mat called a biofilm. By growing the biofilm in the lab on wafers coated with various materials designed to deter the microbes, Mettler can then measure how effective the coatings are. The coatings generally work by having sharp, microscopic spikes that pierce the cell walls of the microbes.

"We were surprised at how well the coatings worked at first," Mettler said. But biofilm did eventually form even on the coatings. The researchers think the cause is the microbes dying on the coating surface and piling up to form a protective layer, Mettler said.

On Earth, a variety of chemicals can be used to help control biofilms, which are notoriously harder to kill than individual bacteria. But on a spacecraft, where water is being recycled for drinking, those chemicals present other problems, Mettler said. Trying to simply scrub out pipes and valves in a cramped space capsule is also problematic.

"I think it could require using a combination of just about every control strategy we know of," said project leader Brent Peyton, professor in the chemical and biological engineering department. That includes coatings, perhaps chemicals for water treatment that can be generated on demand, restricting the nutrients in the water, as well as using ultraviolet light and even high-frequency sound waves to inhibit the biofilm. "But we're hopeful there are solutions," he said. Other MSU researchers have begun collaborating with NASA scientists on some of those strategies, making the coating research part of a larger MSU effort to help the space agency wipe away the biofilm problem.

After learning about the space station biofilm problem from a NASA Jet Propulsion Laboratory scientist at a conference roughly four years ago, NASA scientists were invited to the annual Montana Biofilm Meeting, which brings together dozens of industry representatives, researchers and government officials to exchange the latest findings in biofilm science. In 2019, NASA scientists stayed at MSU after the meeting for a special workshop on spacecraft biofilms. Mettler, then an MSU undergraduate working in Peyton's lab, joined the project before earning her bachelor's in biological engineering from MSU in 2020, and stayed on to conduct the research in Peyton's lab as a graduate student.

Mettler said she looks forward to the Montana Biofilm Meeting each year. "It's amazing how much we're able to learn from each other, and there are so many collaborations that form from those exchanges," she said. This year, she expects lively and productive conversation among the scientists from MSU and NASA.

The Montana Biofilm Meeting is being held virtually this year. Information, including about required registration, can be found at biofilm.montana.edu.