Even the famously resilient tardigrade, often called a “water bear,” struggles to survive in simulated Martian soil, according to a new study published this week in the International Journal of Astrobiology. The research, conducted by a team at Penn State University and collaborating institutions in Poland and the UK, examined the short-term survival rates of two tardigrade species exposed to lab-created Martian regolith.
The study’s findings are crucial for understanding planetary protection protocols as humanity prepares for potential crewed missions to Mars, according to researchers. These protocols aim to prevent both the forward contamination of Mars with Earth-based life and the back contamination of Earth with potential Martian organisms.
Researchers created two types of Martian regolith simulants for the experiment. MGS-1, intended to represent a global average of the Martian surface, and OUCM-1, designed to more closely mimic the chemical composition and mineral makeup of the planet’s soil. Active tardigrades – Ramazzottius cf. Varieornatus and Hypsibius exemplaris – were then introduced to both simulants, and their activity levels were monitored over four days.
The results showed a marked decline in tardigrade activity in the MGS-1 simulant, with some individuals becoming completely inactive within 48 hours. OUCM-1 proved less hostile, with tardigrades maintaining “reasonably energetic” activity throughout the observation period. Notably, the team observed mineral particles accumulating around the tardigrades’ mouths in both simulants, suggesting a physical interaction with the regolith.
“We were a little surprised by how damaging MGS-1 was,” said Corien Bakermans, lead author of the study and a microbiologist at Penn State University. “We theorized that there might be something specific in the simulant that could be washed away.” To test this, the researchers rinsed a portion of the MGS-1 simulant with water. The rinsed simulant significantly improved tardigrade survival rates, indicating the presence of damaging substances that could be removed through a simple washing process.
The study acknowledges several limitations. While the rinsing process offers a potential mitigation strategy, the availability of water on Mars remains a significant logistical challenge. The experiments were conducted using simulated regolith, and the behavior of tardigrades in genuine Martian conditions could differ due to factors like atmospheric pressure and temperature fluctuations. The researchers also emphasize that tardigrades represent only one type of organism, and the survival rates of other microbes, including extremophiles, may vary.
“We grasp a lot about bacteria and fungi in simulated regolith, but very little about how they impact animals—even microscopic animals, like tardigrades,” Bakermans stated. The research team intends to continue investigating the interactions between Martian regolith and various terrestrial organisms to refine planetary protection strategies. The findings, published February 28, 2026, represent a small but significant step toward understanding the challenges of establishing a sustainable presence on Mars and safeguarding both planets from biological contamination.