Recent research from a team in China suggests that atmospheric oxidation played a crucial role in transforming Mars from a warm, wet planet to the cold, arid world we see today. Published in Nature Communications, the study indicates that Mars' early atmosphere was dominated by carbon dioxide and reducing gases, which created a strong greenhouse effect.
The research focuses on the Noachian era, approximately 4.1 to 3.7 billion years ago, a time characterized by high rates of asteroid impacts and possibly abundant surface water. Evidence indicates that early Mars had low iron abundance due to the influence of liquid water, which may have leached iron below the detectable surface range of the Mars Odyssey Gamma-ray spectrometer.
Jiacheng Liu from The University of Hong Kong and colleagues analyzed the distribution of surface iron across various elevations and latitudes on ancient Mars. They found that iron abundance decreased with elevation during the Noachian era, while in more recent terrains, it decreased with latitude. This shift suggests a transition in surface temperature dynamics, influenced by atmospheric changes.
The team posits that icy weathering and low-temperature conditions contributed to surface iron depletion, facilitated by anoxic leaching through freeze-thaw cycles. This gradual atmospheric oxidation ultimately diminished Mars' greenhouse effect, leading to the cold, dry conditions observed today, with ice concentrated at the poles.
Liu emphasizes the significance of this research, noting that the evolution of Mars' surface and atmosphere may have implications for the planet's habitability, particularly in the periglacial environment beneath its cryosphere, which may host stable, long-term liquid water.