Moqui Marbles and Water on Mars

The Navajo Sandstone is an iconic symbol of the American Southwest, renowned for striking rich red to creamy white colors and for sweeping expanses of cross-beds, the remains of ancient sand dunes. Recently I hiked across a vast expanse of these rocks in Snow Canyon State Park, near Zion National Park in the southwestern corner of Utah. During my wanderings, I came across millions of iron-rich nodules, or concretions, that are weathering out of this formation. They reminded me of similar concretions found on Mars, a sign of the presence of water. The Navajo Sandstone concretions are referred to as Moqui (or Moki) marbles. Scholars are uncertain about the name’s origin, but since “moqui” means “the dead” in the Hopi language, the name possibly relates to ancestor worship traditions. The iron-oxide cement tightly binding the marbles in the Navajo Sandstone is composed primarily of hematite (Fe2O3 ) but may also include other iron-oxides such as goethite (FeOOH). Most of the Moqui…