In the past , many spacecraft have had problems with unintentional microbial growth because, similar to a normal home on Earth, they tend to trap moisture released by humans. On the ISS, dust is normally generated by people during their daily activities. However, if these airborne particles are not controlled, they can cause a number of negative health problems for the crew, such as asthma or allergies, and damage building materials and equipment.
To ensure that dust levels aboard the ISS are carefully controlled, astronauts must clean the protective grilles that cover the filters of the space station's ventilation system every week. As part of this study, four individual vacuum bag samples of the dust collected during these housekeeping activities were sent to Dannemiller's team for examination.
After the samples had been incubated for two weeks at different relative humidity levels to simulate a scenario where an unexpected event, such as the temporary failure of a ventilation system, could lead to humidity surges, the analysis revealed that fungi and bacteria can grow in the same concentrated amounts as the dust that accumulates on the floors of residential buildings.
Spacecraft are particularly susceptible to microbial growth because they are enclosed spaces where people constantly exhale moisture. When this moisture accumulates, mold can form, as has been observed in previous space stations such as Mir. Although the ISS has significantly improved moisture controls, unexpected situations can still easily arise, Nastasi said.
