Modeling Virus and Bacteria Populations in Europa's Subsurface Ocean

Area of Science:

• Astrobiology
• Planetary Science
• Microbiology

Background:

• Extreme environments on Earth serve as analogs for extraterrestrial habitability.
• Viruses are crucial in Earth's ecosystems, suggesting potential roles in alien biomes.
• Previous models focused on Earth's icy oceans, not icy ocean worlds like Europa.

Purpose of the Study:

• To investigate the potential role of viruses in transporting organic matter in Europa's ocean.
• To model the dynamics of viral and bacterial populations in Europa's potential sub-ice biosphere.
• To assess the feasibility of a 'viral elevator' mechanism for delivering nutrients.

Main Methods:

• Adapted a viral and bacterial population dynamics model from Earth's Arctic sea ice.
• Utilized Arctic-based studies for proxy parameters for Europa's environment.
• Modeled both closed systems (brine pockets) and open systems with nutrient influx.

Main Results:

• Viral burst size significantly impacts virus-to-bacteria ratio (VBR) and system longevity in closed systems.
• A 'viral elevator' mechanism can support a steady-state sub-ice system in an open environment.
• Resulting sub-ice biofilms could reach approximately 0.1 mm thickness.

Conclusions:

• Viruses may play a key role in transporting dissolved organic matter (DOM) to Europa's sub-ice regions.
• The proposed 'viral elevator' mechanism supports the potential for a habitable sub-ice biosphere on Europa.
• This finding has implications for future astrobiological missions searching for life beneath Europa's ice.