Deep beneath the surface of Mars, in fractured igneous rock, there may be a vast reservoir of liquid water. It could be enough to fill an ocean that would cover the entire surface of Earth’s neighboring planet.
That’s the conclusion scientists have reached based on seismic data collected by NASA’s InSight lander during a mission that helped decipher the interior of Mars. The water, which lies between 11.5 and 20 kilometers below the Martian surface, may have provided favorable conditions for the preservation of microbial life, either in the past or today, the researchers said.
“At these depths, the crust is warm enough for water to exist as a liquid. At shallower depths, the water would be frozen as ice,” said planetary scientist Vashan Wright of the Scripps Institution of Oceanography at the University of California, San Diego, lead author of the study published Monday in the journal Proceedings of the National Academy of Sciences.
“On Earth, we find microbial life deep underground, where rocks are saturated with water and there is an energy source,” added planetary scientist and study co-author Michael Manga of the University of California, Berkeley.
The InSight lander landed in 2018 to study the deep interior of Mars and collect data on the planet’s various layers, from its liquid metal core to its mantle and crust. The InSight mission ended in 2022.
“InSight was able to measure the speed of seismic waves and how they change with depth. The speed of seismic waves depends on what the rock is made of, where it has cracks, and what the cracks are filled with,” Wright said. “We combined the measured seismic wave speed, gravity measurements, and rock physics models. The rock physics models are the same ones we use to measure the properties of aquifers on Earth or to map underground oil and gas deposits.”
The data indicated the existence of this reservoir of liquid water in fractured igneous rocks formed when magma or lava cooled and solidified in the Martian crust, the planet’s outermost layer.
“A middle crust whose rocks are cracked and filled with liquid water best explains both seismic and gravity data,” Wright said. “The water is in cracks. If the InSight site is representative and you extract all the water from the cracks in the middle crust, we estimate that the water on Mars would fill a 1-2 km deep ocean globally.”
The surface of Mars is cold and barren today, but was once warm and moist. That changed more than 3 billion years ago. The study suggests that much of the water that was on the surface of Mars did not escape into space, but seeped into the crust.
“On the surface of early Mars, there was liquid water in rivers, lakes and possibly oceans. The crust of Mars may also have been full of water very early in its history,” Manga said. “On Earth, groundwater penetrated from the surface into the subsurface, and we assume this is similar to the history of water on Mars. This must have happened at a time when the upper crust was warmer than it is today.”
Water would be a vital resource if humanity ever wanted to station astronauts on the surface of Mars or establish some sort of long-term settlement. Mars hosts water in the form of ice in its polar regions and in its subsurface. However, the depth of the apparent subsurface liquid water would make it difficult to access.
“Drilling to these depths is very challenging. An alternative to looking for deep fluids is to look for places where geological activity is ejecting this water, possibly the tectonically active Cerberus Fossae (a region in the northern hemisphere of Mars),” Manga said, but noted that this would need to take into account concerns about protecting the Martian environment. – Reuters
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