The Strength of Mold in Space

As we’ve discussed before, mold problems don’t just exist on Earth. Mold is also a problem for astronauts in space. In fact, they spend hours each week cleaning their environment to prevent the growth of mold. Preventing mold is crucial for protecting astronauts health and the integrity of the shuttle.

Mold was first noticed in space by astronaut David Wolf on the Mir Space Station in 1997. He discovered dozens of bacteria and fungi behind a service panel, in addition to mold on one of the transport vehicles. The fungi managed to crack the quartz glass on the vehicle’s window plus corrode the rubber seals.

Mold and fungi became a recurring problem on the Mir Space Station. Astronauts would often arrive at the station and find it smelled like rotten apples. There are several reasons why mold might have been so prevalent on Mir. First, just like on Earth humans shed skin, which then becomes food for the microbes to feed on. Furthermore, without gravity, and other resistances found on Earth, it’s easier for microbes to spread throughout the station.

In recent years, scientists have spent time trying to understand the mold that is present on the International Space Station. Two of the most common types of mold on the space shuttle are Aspergillus and penicillin. Although they’re not typically harmful to humans, these species could be dangerous to people with weakened immune systems- something astronauts are likely to have.

A recent study led by Marta Cortesao, a microbiologist at the German Aerospace Center, concluded that these molds are quite resilient and can survive 500 to 1000 gray. By comparison, humans will get radiation sickness at .5 gray and will be killed by exposure to 5 gray.

The mold species can also withstand extreme temperature, dry conditions, and chemicals, making them quite hard to kill. Knowing that mold can resist high radiation is important when determining cleaning methods. For instance, large amounts of UV radiation is often used as a hospital disinfectant and has been suggested for cleaning the space shuttle. Cortesaso’s study illustrates that this method would not be effective.

Another factor to consider for mold is the journey to Mars. It is projected to take 180 days, exposing the spacecraft and passengers to .7 gray of radiation. Given the recent research, we now know that mold spores will be able to easily survive this dosage. This means that the crew will need to be prepared with methods for controlling the mold.

While mold may be difficult to kill, it’s important to keep researching it. The more scientists can learn about how mold reacts in space, the easier it will be to prevent. These methods may also have applications for taking care of mold on Earth.


Lovett, Richard A. “Space Station Mold Survives 200 Times the Radiation Dose That Would Kill a Human.” Science Magazine, American Association for the Advancement of Science, 28 June 2019,
Phelan, Matthew. “Why Fungi Adapt so Well to Life in Space.” ScienceLine, New York University, 7 Mar. 2018,
American Geophysical Union. “Space Station Mold Survives 200 Times the Radiation Dose That Would Kill a Human.” Science Daily, Science Daily, 27 June 2019, https://

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