From a new report: As humanity starts packing for a trip to Mars, NASA scientists are studying what not to bring along for the journey. In short, leave the fungus at home. NASA researchers created a closed habitat -- similar to where humans would have to live to survive long space travel or on a new planet -- and looked at fungi and how they grew, publishing their findings in the journal Microbiome. Fungi are "extremophiles" that can survive in the harshest conditions, but in the closed environment of a space station, they can wreak havoc. To see exactly what kind of fungi might colonize astronauts while they colonize Mars, researchers set up an Inflatable Lunar/Mars Analog Habitat, which simulates the closed environment of the International Space Station. They found that certain kinds of fungi increased in number while humans were living inside the habitat, and the weakened immune systems that come with living in a bubble make people more vulnerable to fungi.