Groundwater Recharge on Mars
No matter the degree of complexity, the results converged on the same answer – a minuscule .03 millimeters of groundwater recharge per year on average. That means that wherever rain fell in the model, only an average of .03 millimeters per year could have entered the aquifer and still produced the landforms remaining on the planet today.
For comparison, the annual rate of groundwater recharge for the Trinity and Edwards-Trinity Plateau aquifers that provide water to San Antonio generally ranges from 2.5 to 50 millimeters per year, or about 80 to 1,600 times the Martian aquifer recharge rate calculated by the researchers.
There are a variety of potential reasons for such low groundwater flow rates, said lead author Eric Hiatt, a doctoral student at the Jackson School of Geosciences. When it rained, the water may have mostly washed across the Martian landscape as runoff. Or it may have just not rained very much at all.
Implications for Martian Climate and Exploration
These findings can help scientists constrain the climatic conditions capable of producing rainfall on early Mars. They also suggest a very different water regime on the Red Planet than what exists on Earth today.
“The fact that the groundwater isn’t as big of a process could mean that other things are,” Hiatt said. “It might magnify the importance of runoff, or it could mean that it just didn’t rain as much on Mars. But it’s just fundamentally different from how we think about [water] on Earth.”
The results were published in the journal Icarus. The paper’s co-authors are Mohammad Afzal Shadab, a doctoral student at the Jackson School and faculty members Sean Gulick, Timothy Goudge, and Marc Hesse.
The models used in the study work by simulating groundwater flow in a “steady state” environment where inflow and outflow of water into the aquifer is balanced. Scientists then changed the parameters affecting the flow – for example, where rain falls or the average porosity of the rock – and observed what other variables would have to…
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