Publication
Names
  • A. Valantinas
  • J.F. Mustard
  • V. Chevrier
  • N. Mangold
  • J.L.. Bishop
  • A. Pommerol
  • P. Beck
  • O. Poch
  • D.M. Applin
  • E. Cloutis
  • T. Hiroi
  • K. Robertson
  • S. Pérez-Lopez
  • R. Ottersberg
  • G. Villanueva
  • A. Stcherbinine
  • M.R. Patel
  • N. Thomas
Title
Detection of ferryhydrite in Martian red dust records ancient wet conditions on Mars
Abstract
Iron oxide minerals in Martian dust provide crucial insights into Mars' past climate and habitability. Previous studies attributed Mars' red color to anhydrous hematite formed through recent weathering. Here we show that poorly crystalline ferrihydrite (Fe5O8H · nH2O) is the dominant iron oxide in Martian dust, based on combined analyses of orbital, in-situ, and laboratory visible near-infrared spectra. Spectral analyses indicate that a hyperfine mixture of ferrihydrite and basalt best matches Martian dust observations. Through laboratory experiments and kinetic calculations, we demonstrate that ferrihydrite remains stable under present-day Martian conditions, preserving its poorly crystalline structure. The persistence of ferrihydrite suggests it formed during a cold, wet period on early Mars under oxidative conditions, followed by a transition to the current hyper-arid environment. This finding challenges previous models of continuous dry oxidation and indicates that ancient Mars experienced episodic aqueous alteration before transitioning to its current desert state.
Keywords
spectra, oxides, planetary sciences, Mars
Content
spectral data, spectral data use, planetary sciences
Year
2025
Journal
Nature Communications
Document type
article
Publication state
submitted