Early Mars: A Potential Haven for Microbial Life
Research suggests that Mars may have been habitable for methanogenic microorganisms around 3.7 billion years ago. This raises questions about the possibility of life on the Red Planet, even if it may not be present today.
A Subsurface World of Microorganisms
Mars’ early atmosphere was likely denser, and the planet may have been filled with water. This period, known as the “Noachian” era, spanned from 4.1 to 3.7 billion years ago. During this time, Mars could have supported hydrogenotrophic methanogens, simple microbial organisms that consume hydrogen and carbon dioxide, producing methane as waste.
Simulating Early Martian Conditions
Scientists used a state-of-the-art model to study the effects of methanogenic hydrogenotrophy on early Mars. By combining a photochemical climate model and a model of the early Martian crust, they analyzed the atmospheric composition, climate, thermal properties of the crust, and gas exchange between the crust and atmosphere.
Methane-Releasing Microbes on Mars
The simulation revealed that methane-releasing microbes could have thrived below the Martian surface. These microorganisms convert chemical energy from their environment, releasing methane as waste. On Earth, they inhabit extreme habitats, such as hydrothermal vents, and support entire ecosystems.
Implications for Life on Mars
The team theorized that methane-releasing microbes on Mars could have lived just below the surface, protected from radiation by a few centimeters of earth. However, extracting hydrogen from the thin atmosphere would have endangered the planet’s protective shell, causing the temperature to plummet and forcing microbes to seek deeper habitats.
Searching for Evidence of Life on Mars
Researchers suggest that the best places to search for evidence of past life on Mars are Hellas Planitia and the Jezero crater. NASA’s Perseverance rover is collecting rocks in the crater of Isidis Planitia, which will be returned to Earth in the next decade. The discovery of methanogenic life on modern-day Mars would provide strong evidence supporting the model’s predictions.