Research shows that ancient Mars had minimal groundwater recharge, significantly different from Earth’s water dynamics, influencing our understanding of its climate and facilitating future Mars missions. Mars was once a wet world. The Red Planet’s geological record shows water flowing across the surface, from river deltas to valleys punctuated by major floods.

But a new study shows that no matter how much rain fell on the surface of ancient Mars, very little of it seeped into groundwater in the planet’s southern highlands. A graduate student at the University of Texas at Austin made the discovery by modeling the dynamics of groundwater recharge for an aquifer using a variety of methods, from computer models to simple offline calculations.

Groundwater Replenishment on Mars

Regardless of the degree of complexity, the results converged on the same answer: an inadequate replenishment of groundwater by 0.03 millimeters per year on average. This means that wherever it rained in the model, only an average of 0.03 millimeters per year could enter groundwater and form the landforms that remain on the planet today.

By comparison, annual groundwater recharge rates for the Trinity Plateau and Edwards-Trinity Plateau aquifers that provide San Antonio’s water typically range from 2.5 to 50 millimeters per year; This is approximately 80 to 1,600 times the recharge rate of the Martian aquifer horizon calculated by the researchers.

There are a number of potential reasons for such low groundwater flow, said lead author Eric Hyatt, a doctoral student in the Jackson School of Geological Sciences. When it rained, the water may have flowed mostly as streams across the Martian surface. Or maybe it wasn’t raining at all.

Implications for Martian climate and exploration

These findings could help scientists constrain the climate conditions that could produce precipitation on early Mars. They also suggest that the water regime on the Red Planet is completely different from what exists on Earth today.

“The fact that groundwater is not that big of a process could mean there are other things going on,” Hyatt said. “This could increase the importance of flow, or could mean that Mars doesn’t get a lot of rain. But this is fundamentally different from what we thought.” [воду] On Earth”.

The results were published in the journal Icarus. The paper was co-authored by Mohammad Afzal Shadab, a postdoctoral researcher at the Jackson School, and faculty members Sean Gulick, Timothy Gouge, and Mark Hesse.

The models used in the study work by simulating groundwater flow in a “steady-state” environment where water inflow and outflow to the aquifer is balanced. The scientists then varied the parameters that affected the flow (such as where the rain fell or the average porosity of the rock) and observed what other variables needed to change to maintain a steady state and how likely those loads were.

Although other researchers have modeled groundwater flow on Mars using similar techniques, this model is the first to include the influence of oceans that existed on the surface of Mars in the Hellas, Argyrus, and Borealis basins more than three billion years ago.

The study also includes modern topographic data collected by satellites. According to Hyatt, the modern landscape still preserves one of the planet’s oldest and most influential topographic features: the extreme elevation difference between the northern hemisphere (lowlands) and southern hemisphere (highlands), known as the “great dichotomy.” The dilemma preserves signs of past groundwater upwelling, when groundwater rose from the aquifer to the surface. Researchers used geological signatures of past uplift events to evaluate the performance of various models.

Using a variety of models, the researchers found that an average groundwater recharge rate of 0.03 millimeters per year was the rate most consistent with what is known about the geological record.

The research isn’t just aimed at understanding the Red Planet’s past. It also has implications for future Mars exploration. Understanding the flow of groundwater can help determine where water would be found today, Hyatt said. Whether you’re looking for signs of ancient life, trying to support human explorers, or making rocket fuel to return to Earth, it’s important to know where water is most likely to be found.