Physarum polycephalum is a single cell with shocking abilities: solving complex optimization problems and surviving extreme environments by forming long-lasting spores. Its responses to light stressors, such as UV and infrared radiation, make it a compelling model for studying how life might adapt to harsh environments. Could this simple organism reveal how life could adapt beyond Earth? Early data from Hypatia I mission hint at infrared adaptability inviting deeper research.
Physarum polycephalum, commonly referred to as “the blob,” is a plasmodial slime mold notable for being a multinucleate single cell that exhibits surprisingly complex behavior. In its plasmodial stage, it forms an amoeba-like organism that can span several centimeters and move at rates of a few centimeters per hour. Despite being unicellular, Physarum exhibits remarkable learning-like abilities for a single-celled life form. Through its movements, it can encode information about previously traveled paths, discard inefficient routes, and optimize connections between nutrient sources. These behaviors have fascinated researchers because they challenge assumptions that learning and memory are exclusive to organisms with nervous systems.
Beyond these surprising behavioral traits, slime molds are also extremely resilient. When faced with environmental stressors—such as limited food availability or unfavorable climatic conditions—it transitions to a spore-forming stage. These spores are exceptionally durable and can remain dormant for decades, reactivating only when conditions are suitable. This level of endurance has positioned Physarum as an intriguing organism for understanding survival strategies in harsh environments.
Due to the ease with which its life cycle can be observed with the naked eye, Physarum polycephalum has served as a valuable model organism across multiple areas of biological research. Scientists have used it to investigate cell cycle regulation, cellular differentiation, development, and responses to physical stimuli. Because it reacts measurably to environmental factors such as light, humidity, and nutrient, it provides an accessible system for studying how cells sense, adapt to, and endure environmental challenges.
This adaptability becomes particularly relevant when considering extraterrestrial environments. Mars, for example, presents multiple stressors that differ dramatically from Earth. Located approximately 1.4 times farther from the Sun than Earth, Mars receives roughly half the solar irradiance. Its atmosphere, which is thin and lacking protective levels of water vapor and ozone, fails to filter solar radiation effectively. Consequently, the Martian surface is exposed to higher levels of UV and infrared light. Furthermore, the absence of a global magnetic field—unlike Earth’s—allows high-energy particles such as X-rays and gamma rays to reach the surface with little obstruction.
These conditions raise questions about biological adaptability beyond Earth. Physarum is highly light-sensitive; exposure to light can inhibit its movement and initiate spore formation. Understanding how UV and infrared radiation influence its behavior and sporulation could shed light on how life might cope with Martian-like environments. If Physarum can adapt or survive under simulated Martian conditions, this may provide clues regarding the feasibility of life on Mars today or in the planet’s past. It may also inform hypotheses about how early terrestrial life endured before Earth developed a protective atmosphere and magnetic field.
Three sclerotia of Physarum polycephalum (LU strain) were cultivated and grown until big enough to provide 4 clones to be tested simultaneously in different conditions:
- One sample being the control sample, with no stimulation.
- A second sample on an inclined plate to evaluate the effect of gravity.
- A third one being stimulated with IR light.
- And finally, a fourth sample, stimulated with UV light.
Preliminary data from the Hypatia I mission suggest that Physarum may possess adaptive responses to infrared radiation. However, these findings require further experimentation to validate and characterize.
