Starship Asterisk*

New research suggests that the bulk of clay minerals on Mars could have been formed as the planet’s crust cooled and solidified, not by later interactions with water on the surface as has long been assumed.

[img3="Mars may have been enveloped in a thick, steamy atmosphere as the planet's crust cooled and solidified. That steam bath could have created the clay minerals that have long been attributed to water flow on or just beneath the surface."]https://news.brown.edu/files/styles/hor ... rtwork.jpg[/img3][hr][/hr]

Planetary scientists from Brown University have proposed a new scenario for the formation of ancient clay minerals on Mars that, if shown to be true, could rewrite the early history of the red planet.

There are thousands of ancient phyllosilicate outcrops on the Martian surface. Phyllosilicates, or clays, are formed by the interaction of water with volcanic rock, leading many scientists to conclude that there must have been sustained surface water, groundwater or active hydrothermal systems at some point in Martian history. But the new research, published in the journal Nature, suggests that the clays may have formed during the creation of the Martian crust itself, long before any water flowed on the planet.

Backed by lab experiments and computer models, the researchers lay out how the scenario would have worked. In the very early solar system, Mars and other rocky planets are thought to have been covered by oceans of molten magma. As the Mars magma ocean began to cool and solidify, water and other dissolved volatiles would be outgassed to the surface, forming a thick, steamy atmosphere surrounding the planet. The moisture and heat from that high-pressure steam bath would have converted vast swaths of the newly solidified surface to clay. As the planet then evolved over billions of years, volcanic activity and asteroid bombardments would have covered the clays in some places and excavated them in others, leading to the widespread but patchy distribution seen on the surface today. ...

Martian clays present a conundrum: the models proposed to explain their formation require conditions that are not predicted by computational climate simulations. Experiments now suggest an alternative scenario.

• Kevin M. Cannon, Stephen W. Parman, John F. Mustard
  Nature 552(7683):88 (07 Dec 2017) DOI: 10.1038/nature24657