Can the cleanest rooms in the world also support life with the potential to reach Mars? NASA’s highly cleaned spacecraft assembly clean rooms, which are intended to prevent even the most resilient Earthly microorganisms from contaminating another planet, have only recently provided the astonishing response to that question. Researchers have discovered 26 new bacterial species that are alive and well in these harsh conditions.
This discovery was a result of swabs conducted at the Kennedy Space Center’s Payload Hazardous Servicing Facility, where the Phoenix Mars Lander was built back in 2007. “It was a true ‘stop and re-check everything’ moment,” said Rosado of the King Abdullah University of Science and Technology. The microbes were coping with nutrient deprivation and sterilization conditions with constant air exchange with HEPA filters, UV irradiation, chemical detergents, and humidity conditions. The genetic sequencing identified resilience strategies against chemical cleaning agent resistance, the capacity to produce biofilms with a strong adhesive in very small surface niches, DNA repair machinery against radiation damage, and the ability to produce stress-resistant spores.
Such characteristics are far from trivial. Biofilm matrices or the aggregate extracellular polymer matrix shield microbial populations against chemical and physical disinfection. This was observed already on the International Space Station with biofilms precipitating the malfunction of water recovery systems and the degradation of stainless steel surfaces. Then there is the dormant state and the development of spores that guarantee survival so that microbes can live for up to years before conditions become favorable for renewed multiplication. There are also extremophiles such as radiation-resistant bacteria like Deinococcus radiodurans that can withstand up to 10,000 Gy of ionizing radiation, exceeding the lethal dosage of 1,000 times that of the lethal dosage for a human.
These clean-room organisms possess some signatures of these stress-resistance mechanisms, including homologous recombination pathways that repair double-strand breaks in DNA, as well as enzymes that detoxify radiation-induced reactive oxygen species. The presence of these mechanisms suggests that these microbes could, through accidental launch, survive the interplanetary transfer conditions of vacuum, extremely low temperatures, and strong UV radiation. This is exacerbated by the fact that conditions on the Martian surface are similar to those that these microbes can survive.
In order to test this risk, Rosado’s team is constructing an Earth planetary simulation chamber at Saudi Arabia, which is meant to simulate Mars or space environments. Based on designs like the SpaceQ chamber, it would be able to operate under pressure from 10⁻⁵ mbar up to atmospheric, at temperature ranges from 163 K to 423 K, where there would be cooling plates made of liquid nitrogen simulating the bitterly cold nighttime environments, as well as heating jackets. In addition, it would have the ability to inject trace amounts of water vapor simulating the water cycle in the near-surface Martian environment, as well as a high-intensity ultraviolet lamp that simulates the kind of solar radiation found on Mars. In this environment, controlled concentrations of stresses environment such as vacuums, CO²-rich environment, ultraviolet radiation, and brine formation might have been able to make the cleanroom microbiota survive and adapt.
However, it is not just Mars missions that are affected. In view of biofilms and dormant spores, which have already posed difficulties for sterilization in compact space habitats, studies on futuristic anti-bacterial coatings, nanoparticle-containing surfaces, and silver-compound-based biocides have been recommended. In microgravity, multi-species biofilms could display unexpected phenomena, like changes in gene expression, increased drug resistance, and unexpectedly high corrosion rates, which do not obtain for single species biofilms on Earth. This indicates that there is a need for comprehensive monitoring solutions, including machine learning for early detection of biofilms on space mission components before component failures take place.
As an engineer, it is a matter of exploring the edges of the current planetary protection policy framework to see what the future may hold. The idea that clean rooms, regardless of their sophistication, are not equivalent to “no life” is important to the issues at stake here. The intermittent and hardy organisms identified are indeed “excellent test organisms” for validation of decontamination and detection techniques, in Rosado’s words: It will be necessary to have a coordinated sampling of several facilities simultaneously and a set of parallel standard stress-response experiments to differentiate the attributes fundamental to life as it exists somewhere in the universe from those relevant to biotechnology.
The key to this determination, in a new age of manned Mars exploration missions and SAMPLE return missions, is to recognize why it matters to ensure a successful effort to find life elsewhere in the universe does not plant a flag—accidentally or otherwise—here on Earth.
