Chemical weathering over hundreds of millions of years of greenhouse conditions on Mars

Chemical weathering profiles on Mars, consisting of an upper Al clay-rich, Fe-poor layer and a lower Fe/Mg clay-rich layer, are believed to have formed due to precipitation-driven top-down leaching in an ancient, reducing greenhouse climate. This study uses remote sensing, spectroscopy, topographic data, and crater chronology to analyze >200 weathering profiles across the southern highlands of Mars. The findings suggest a consistent single stratigraphic relationship (Al/Si materials over Fe/Mg clays), indicating either a single climate warming event or, more likely, chemical resetting of weathering horizons during multiple events. While individual profile formation may have taken ~10⁶-10⁷ years, their presence in deposits dating from the Early Noachian to the Hesperian suggests weathering occurred over a vast geologic time range, peaking around 3.7-3.8 billion years ago.

Binlong Ye, Joseph R. Michalski