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A study reveals that ancient Mars had a significantly low groundwater recharge rate, suggesting that despite evidence of water on its surface, the planet’s water regime was very different from that on Earth. This finding, derived from various modeling methods, highlights the challenges in understanding Mars’ hydrological past and has implications for future exploration and the search for water resources. (Artist’s concept). Credit: SciTechDaily.com
Research indicates ancient Mars It had minimal groundwater recharge, which differs greatly from Earth’s water dynamics, affecting our understanding of its climate and aiding future missions to Mars.
Mars was once a wet world. The geological record of the Red Planet shows evidence of water flowing on the surface, from river deltas to valleys carved by massive flash floods.
But a new study shows that no matter how much rain fell on the surface of ancient Mars, very little seeped into an aquifer in the planet’s southern highlands.
A graduate student at the University of Texas at Austin made the discovery by modeling groundwater recharge dynamics for the aquifer using a variety of methods, from computer models to simple general calculations.
Mars in true color, taken by the Emirates Mars Mission in August 2021. Credit: Kevin M. Gill
Groundwater recharge on Mars
No matter the degree of complexity, the results converged on the same answer: a minuscule groundwater recharge of 0.03 millimeters per year on average. That means that wherever rain fell in the model, only an average of 0.03 millimeters per year could have entered the aquifer and still produced the landforms left on the planet today.
For comparison, the annual groundwater recharge rate of the Trinity and Edwards-Trinity Plateau aquifers that supply water to San Antonio generally ranges between 2.5 and 50 millimeters per year, or about 80 to 1,600 times the rate of Martian aquifer recharge calculated by researchers.
There are a variety of potential reasons for such low groundwater flow rates, said lead author Eric Hiatt, a doctoral student in the Jackson School of Geosciences. When it rained, the water may have mostly traveled across the Martian landscape as runoff. Or maybe it just hasn’t rained much.
Implications for Martian climate and exploration
These findings may help scientists limit the weather conditions capable of producing rain in the early stages of Mars. They also suggest a very different water regime on the Red Planet than exists on Earth today.
“The fact that groundwater isn’t that big of a process could mean that other things are,” Hiatt said. “It could magnify the importance of the runoff, or it could mean that it just didn’t rain as much on Mars. But it is fundamentally different from how we think about (water) on Earth.”
The results were published in the journal. Icarus. Co-authors of the paper are Mohammad Afzal Shadab, a Jackson School doctoral student, and faculty members Sean Gulick, Timothy Goudge, and Marc Hesse.
Lead author Eric Hiatt, a doctoral student at UT’s Austin Jackson School of Geosciences, with a Mars globe. Credit: University of Texas at Austin/Jackson School of Geosciences
The models used in the study work by simulating groundwater flow in a “steady state” environment where the input and output of water to the aquifer are balanced. The scientists then changed the parameters that affect the flow (for example, where the rain falls or the average porosity of the rock) and looked at what other variables would have to change to maintain the steady state and how plausible those loadings are.
While other researchers have simulated groundwater flow on Mars using similar techniques, this model is the first to incorporate the influence of oceans that existed on the surface of Mars more than three billion years ago in the Hellas, Argyre basins. and Borealis.
The study also incorporates modern topographic data collected by satellites. The modern landscape, Hiatt said, still retains one of the oldest and most influential topographic features on the planet: an extreme difference in elevation between the northern hemisphere (the lowlands) and the southern hemisphere (the highlands), known as the “great dichotomy”. The dichotomy preserves signs of past groundwater upwellings in which groundwater rose from the aquifer to the surface. The researchers used geological markers of these past upwelling events to evaluate the different model results.
Through different models, the researchers found that the average groundwater recharge rate of 0.03 millimeters per year matches more closely what is known about the geological record.
The research is not just about understanding the Red Planet’s past. It also has implications for future Mars exploration. Understanding groundwater flow can help you know where to find water today, Hiatt said. Whether you’re looking for signs of ancient life, trying to sustain human explorers, or making rocket fuel to return to Earth, it’s essential to know where the water would likely be.
Reference: “Limited recharge of the southern highland aquifer on early Mars” by Eric Hiatt, Mohammad Afzal Shadab, Sean PS Gulick, Timothy A. Goudge and Marc A. Hesse, September 9, 2023, Icarus.
DOI: 10.1016/j.icarus.2023.115774
The research was funded by POTthe University of Texas Geophysics Institute and the UT Planetary Habitability Center.