Data from the late Mars InSight lander continues to pay dividends, with the latest findings suggesting liquid water is abundant in the Martian mid-crust (about 7 to 12 mile depths).
The discovery comes via a trio of scientists from the University of California San Diego and UC Berkeley, who said in a paper published yesterday that they've been reviewing seismological data from InSight to learn more about Mars' water cycle.
"A mid-crust composed of fractured igneous rocks saturated with liquid water best explains the existing data," the researchers wrote. "Our results have implications for understanding Mars' water cycle, determining the fates of past surface water, searching for past or extant life, and assessing in situ resource utilization for future missions."
We've long suspected water was present on Mars, and recent scientific missions to the Red Planet have repeatedly found evidence that our planetary neighbor once harbored surface rivers, lakes, and oceans.
A process of climate change on Mars may be the reason all that surface water vanished around three billion years ago, leaving naught but polar ice caps and mineral-bound water beneath the surface. Paper coauthor Michael Manga of UC Berkeley's department of Earth and planetary science said the findings in the latest paper suggest there might be a lot more liquid water on Mars than previously believed.
"Finding present-day liquid water in the form of groundwater in the crust completes a picture of Mars' water cycle," Manga told us in an emailed statement. "Just as on Earth where groundwater is connected to the surface through rivers and lakes, this was surely the case on early Mars as well."
In other words, while lots of water was lost along with Mars' atmosphere, there's a good possibility a lot of it retreated underground.
The authors said in their paper that the water was discovered by examining ground motion data collected by InSight's seismograph. By matching InSight data with rock physics models, examining how quickly seismic waves moved through Mars' crust and doing some modeling, the only good explanation is the presence of liquid water, the team concluded.
The bad news: It's really deep
The water, Manga explained, exists within fractures in Mars' mid crust. InSight, which landed near Mars' equator in the relatively flat planes of Elysium Planitia, was only able to gather data about the ground beneath it. If its data is representative of the rest of the planet, there's a lot of water buried down there.
"If the InSight location is representative and you extract all the water from the fractures in the mid-crust, we estimate that the water would fill a 1-2 km deep ocean on Mars globally," Manga told us.
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There's a catch, though: The water is buried between about 7 to 12 miles (11.5 and 20 km) below the surface, making it nearly impossible to access.
"On Earth it is difficult to drill deep holes – it takes a lot of infrastructure and energy," Manga said. "Engineers also circulate mud and other fluids to help with the drilling. So a huge amount of resources would need to be brought to Mars to drill that deep."
For reference, the deepest hole ever drilled on Earth is the Kola Superdeep Borehole in Murmansk, Russia, plunges to around 7.5 miles beneath the surface of our planet, and it took 20 years to reach that depth. The project was abandoned nearly 20 years ago, and we haven't dug a deeper hole since.
In other words, if we're going to drill for water on Mars, we probably need to go somewhere else.
"Looking for places where geological activity expels this water, possibly the tectonically active Cerberus Fossae, is an alternative to looking for deep liquids," Manga suggested.
Of course, extracting water somewhere else relies on InSight's findings reflecting the broader presence of water beneath Mars' rocks and soil, which isn't a guarantee.
Manga hopes additional seismometers will eventually find their way to Mars to verify his team's findings aren't geographically constrained, and he would also like to see similar readings taken on ocean worlds like Enceladus and Europa for comparison.
Getting the Mars Sample Return mission off the ground would also "be a start," Manga told us.
"The groundwater we see [on Mars] is a record of that past," Maga said. "We need to work on understanding that history: what, where, when, and how." ®
