New evidence exists for hidden water reservoirs and rare magmas on ancient Mars

The study, led by Rice University’s Cin-Ty Lee, shows that the thick crust of the Southern Highlands – up to 80 kilometers long in some areas – was hot enough during the Noachian and early Western periods (3-4 billion years ago) that Experiencing partial melting in the lower crust. This process, driven by radioactive heating, could create large volumes of siliceous magma, such as granite, and support underground aquifers beneath the frozen surface.

“Our results show that Mars’ crustal processes are much more active than previously thought,” said Lee, the Harry Carrothers Wyss Professor of Geology and professor of Earth, environmental and planetary sciences. “The thick crust of the Southern Highlands not only allows the production of granitic magma without plate tectonics, but also creates the thermal conditions for stable groundwater aquifers (liquid reservoirs) on a planet we often think of as dry and frozen.”

The research team, which included Rice University professors Rajdeep Dasgupta and Kirsten Siebach, postdoctoral researcher Duncan Keller, and Lunar and Planetary Institute graduate students Jackson Borchardt, Julin Zhang and Patrick McGovern, used advanced thermal models to reconstruct the thermal state of Mars. epoch and early Western periods. By taking into account factors such as crustal thickness, radioactive heat production and mantle heat flow, the researchers modeled how heat could affect the likelihood of crustal melting and groundwater stability.

Their model shows that regions of the Earth’s crust thicker than 50 kilometers undergo extensive partial melting, either directly through dehydration melting or indirectly through fractional crystallization of intervening magmas to produce felsic magmas. In addition, due to elevated heat flow, the thick crust of the Southern Highlands will sustain large amounts of groundwater, with aquifers extending several kilometers below the surface.

The study challenges the idea that granite is unique to Earth, showing that even in the absence of plate tectonics, Mars could produce granitic magma through radioactive heating. These granites may still be hidden beneath basalt flows in the southern highlands, providing new insights into the geology of Mars. Additionally, the study highlights the potential for ancient groundwater systems to form in the southern highlands of Mars, where high surface heat fluxes reduced the extent of permafrost and created stable underground aquifers. These reservoirs may be periodically accessed by volcanic activity or impacts, causing intermittent flooding events on the Earth’s surface.

The findings have important implications for habitability because the presence of liquid water and the ability to produce granitic magma, which often contains elements critical to life, suggests that Mars’ southern highlands may have been more hospitable to life in the past than previously thought.

“Granites are more than just rocks; they are geological archives that tell us about the planet’s thermal and chemical evolution,” said Dasgupta, Morris Ewing Professor of Earth, Environmental and Planetary Sciences. “On Earth, granite is associated with tectonics and water cycles. The fact that we see evidence of similar magma on Mars through deep crustal remelting emphasizes the complexity of this planet and its potential to harbor life in the past. .

The study highlights areas on Mars where future missions may focus on detecting granite or exploring ancient reservoirs. For example, large craters and fissures in the Southern Highlands offer a glimpse into Earth’s deep crust.

“Each insight into processes in Mars’ crust brings us closer to answering some of the deepest questions in planetary science, including how Mars evolved and how it could support life,” Seebach said. “Our research sets us up for the search for these answers. Provides a road map of where to look and what to look for.”

This research was made possible by NASA grant 80NSSC18K0828.