Self-assembling iron oxyhydroxide/oxide tubular structures: laboratory-grown and field examples from Rio Tinto

Area of Science:

• Astrobiology
• Geochemistry
• Mineralogy

Background:

• Rio Tinto, Spain, is an analog for early Mars environments.
• Tubular structures have been discovered in its riverbed and ancient terraces.
• This is the first report of such structures in this specific location.

Purpose of the Study:

• To investigate the origin and formation of newly discovered tubular structures in Rio Tinto.
• To assess the potential astrobiological significance of these structures and their formation mechanisms.
• To explore the implications for understanding early Mars habitability.

Main Methods:

• Field sampling of tubular structures from Rio Tinto terraces.
• Laboratory experiments simulating abiotic self-assembly via templated precipitation (chemical gardens).
• Fluid-mechanical scaling analysis to assess mechanism plausibility.

Main Results:

• Discovery of previously unreported tubular structures in Rio Tinto.
• Successful laboratory replication of similar structures using iron oxyhydroxide self-assembly.
• Demonstration of the plausibility of abiotic formation via fluid jet templated precipitation.
• Observation of iron mineral oxidation gradients across tube walls.

Conclusions:

• The tubular structures in Rio Tinto likely formed through an abiotic chemical garden mechanism.
• These structures, while not biosignatures themselves, provide insights into potential energy gradients.
• The findings contribute to understanding potentially habitable environments on early Mars.