Are there diseases in space?

Episode Summary

Executive Summary: The episode investigates whether diseases could exist in space or on other planets and whether Earth microbes could contaminate other worlds. Experts explain that hardy microbes can survive extreme conditions, astronauts can experience weakened immunity in space, and planetary protection protocols are essential to prevent backward and forward contamination during Mars exploration.

Main Topics: Could diseases exist in space? (Priority: 5/5): The listener question explores whether alien environments might host microbes that could infect humans or be brought back to Earth. Microbial survival in extreme environments (Priority: 5/5): Astrobiologist Michaela Musilova explains that some bacteria form spores and may endure radiation, cold, and desiccation for very long periods. Spaceflight and astronaut health (Priority: 5/5): NASA astronaut and microbiologist Kate Rubins describes how microgravity and space stress can dysregulate immune function and reactivate dormant viruses like shingles. Planetary protection and contamination control (Priority: 5/5): ESA’s Silvio Cinibaldi outlines containment strategies to keep Martian samples and spacecraft from contaminating Earth or other planets. Engineering clean spacecraft for Mars (Priority: 4/5): Airbus engineers describe sterilization, material choices, and low-spore limits used in the ExoMars rover program to reduce false positives and biological contamination. Earth microbes hitchhiking to Mars (Priority: 5/5): The episode argues that contamination from Earth to Mars is already likely, complicating any future claim of discovering native Martian life.

Key Arguments: Microbes are the most plausible form of life to survive in space because many bacteria can enter hardy spore states that protect DNA from radiation. Space itself and planets like Mars are hostile environments, so if life exists there it is more likely to be simple microbial life than complex organisms. Astronauts may be more vulnerable to infection in space because the immune system becomes dysregulated and depressed in microgravity. Dormant viruses already carried by astronauts, especially shingles/herpes family viruses, can reactivate during missions. Returning samples from Mars poses a backward contamination risk, so agencies plan containment and quarantine procedures before any Earth exposure. It is nearly impossible to make spacecraft completely sterile, so planetary protection focuses on minimizing microbes and preventing those likely to proliferate on other worlds. Human missions and robotic probes have probably already transported Earth microbes to Mars, meaning future life-detection missions must rule out contamination first.

Data Points: Astronaut time on ISS: 300 days - Kate Rubins spent this long on the International Space Station conducting microbiology research. Astronauts with shingles/herpes family viral DNA or RNA detected: 40–60% - Studies cited by Rubins found dormant herpes-family viruses in a substantial share of astronauts. Moon response time to medical care: about 5 days away - Used to illustrate the difficulty of treating infections on future lunar missions. Mars mission duration: 2.5 years - Rubins noted that a Mars mission would be long and return would not be immediate once engines are burned. Mars rover spore requirement: less than 10,000 bacterial spores across the complete surface - ExoMars planetary protection target for the rover’s exterior. Achieved rover contamination level: 10% of the required limit - Airbus team reported exceeding cleanliness goals by keeping spores far below the threshold. Earth microbes shed by humans: millions every 24 hours - Compared with the extremely low contamination levels required for spacecraft assembly. Mars sample-return status: postponed - NASA’s planned Mars sample return mission was delayed, but contamination precautions were still discussed.

Pivotal Quotes: "Rather safe than sorry." — Dr. Michaela Musilova: Her guidance on handling the possibility of microbes in Martian samples and preventing backward contamination. "We have like a containment of a containment, so three layers of a containment." — Silvio Cinibaldi: Explaining the layered protection planned for Mars sample handling. "Once you burn your engines to go to Mars, you're not coming back." — Kate Rubins: Describing why infection prevention and medical planning matter more on deep-space missions.

Implications: The episode shows that future space exploration depends on strict planetary protection and onboard medical planning. It also warns that Earth microbes may already complicate the search for alien life, making contamination control central to science credibility.