Scientists have explained that vast amounts of water may be trapped deep within the crust of Mars, raising new questions about the possibility of life on the red planet.
According to scientists, more than three billion years ago, the surface of Mars contained not only lakes and rivers, but also oceans. However, when the planet lost its atmosphere, these bodies of water disappeared. Today, only permafrost ice is visible at the planet’s poles.
Although some of the water is believed to have been lost in space, research suggests that this is not the full truth and that the water may have been trapped in minerals, buried as ice, or even existed in liquid form deep within the Earth’s crust.
Now scientists say their calculations suggest that huge amounts of liquid water are trapped in rocks about 11.5 to 20 kilometers below the surface of Mars.
“Our estimate of the amount of liquid water exceeds the amount of water that would have filled possible oceans on Mars,” said Dr. Vashan Wright, co-author of the study from the Scripps Institution of Oceanography at the University of California, San Diego.
Writing in the Proceedings of the National Academy of Sciences, Wright and his colleagues report how they made their calculations based on gravity data from Mars and measurements from NASA’s InSight lander, which show how the speed of seismic waves – caused by Marsquakes and meteorite impacts – changes with depth in the red planet’s crust.
“A mid-crust whose rocks are fractured and filled with liquid water best explains both seismic and gravity data,” Wright said.
Wright added that if measurements at the Insight lander site were representative of the entire planet, the amount of water trapped in the rock fractures would be enough to fill an ocean one to two kilometers deep on Mars.
“On Earth, groundwater seeped from the surface into the subsurface, and we assume that this process also occurred on Mars,” he said. “The infiltration must have occurred at a time when the upper crust was warmer than it is today.”
While the results do not rule out the possibility that water may also have been lost in space or trapped in minerals, Wright said the work has allowed scientists to reevaluate the relative contribution of these different mechanisms to the loss of surface water on Mars in the past.
The study also raises a tantalizing possibility.
“The presence of water does not mean there is life, but it is believed that water is an important prerequisite for life,” Wright said. “We know that life can exist deep underground on Earth where there is water. At least the middle crust of Mars contains a key ingredient for habitability and life as we know it.”
Bethany Ehlmann, a professor of planetary science at the Keck Institute for Space Studies who was not involved in the work, said it was now necessary to make a definitive measurement that would show whether there is liquid water in the depths of Mars – and if so, exactly where it is located.
“Where there is liquid water on Earth, there is life. So if there are liquid aquifers on Mars now, they are a priority target in the search for life,” she added.
Dr Jon Wade of Oxford University said he would not be surprised to see life on Mars. “In its early history, Mars was as favorable for simple life as Earth, if not more so,” he said.
Dr Steven Banham of Imperial College London added that identifying liquid water in the middle crust would also help geophysicists and geologists understand the internal structure and behaviour of Mars.
However, Banham expressed doubts that this water could serve as a resource for manned missions to Mars.
“Yes, the amount of water in the Earth’s crust is potentially huge, but it will be difficult to access or use,” he said. “It may not make much difference to human exploration, at least initially.”
