Mars may harbour life in vast underground reservoir

A vast reservoir of liquid water is hidden beneath the surface of Mars and may harbour life, US researchers have concluded.
The red planet is now a frozen desert but evidence of ancient rivers, deltas and oceans is etched into its surface, suggesting that it glistened with water more than three billion years ago.
A new analysis suggests that much of that liquid water did not, as widely thought, escape into space when the planet lost its atmosphere but instead filtered down into the crust, where temperatures are warmer.
The readings suggest that enough liquid water could be trapped to cover all of Mars, which is about half the diameter of the Earth, with an ocean up to about a mile deep.
“The water is the same as groundwater on Earth,” said Vashan Wright, a geophysicist at Scripps Institution of Oceanography at the University of California, San Diego, who led the study.
It would be enormously challenging for any future settlers to drill down to extract it, however. The liquid is thought to be stored in tiny cracks and pores in rock between seven and twelve miles beneath the surface. The deepest man-made hole on Earth, the Kola Superdeep Borehole, is about 7.6 miles deep and took the Soviets almost 20 years to drill.
On Mars, all of the necessary equipment would have to be imported at great expense. “It would be better to look for places where geological activity might expel groundwater,” Wright said.
• Nasa finds rock on Mars that ‘may have hosted life’
Even at great depths, however, his team believe the Martian groundwater could harbour microbial life. “I don’t see why [the underground reservoir] is not a habitable environment,” Michael Manga, a professor at the University of California, Berkeley, said.
“It’s certainly true on Earth — deep, deep mines host life, the bottom of the ocean hosts life. We haven’t found any evidence for life on Mars, but at least we have identified a place that should, in principle, be able to sustain life.”
Manga and his colleagues analysed data gathered by British-built instruments carried to Mars in 2018 by Nasa’s InSight spacecraft. These produced the first measurements of seismic activity on another planet, detecting and measuring hundreds of “marsquakes”.
Some of the larger marsquakes were traced to a geologically active area known as the Cerberus Fossae, about 1,000 miles from InSight. They may be the result of pockets of magma cooling and contracting in an area that was volcanically active a few million years ago. The lander also recorded seismic activity from meteor strikes.
These events produced seismic waves, the speed of which depended on the material they were passing through. This allowed geophysicists to build up a picture of the planet’s interior.
At the same time, the strength of gravity over the planet’s surface was mapped by tracking the position of satellites orbiting Mars. Gravity depends on mass and, therefore, density. This means that maps that show gravity and surface elevation can be converted to show the density of the crust, providing clues on its composition.
“The speed of seismic waves depends on properties of rocks — what they are made of, are they cracked, what fills the cracks,” Wright said. “A mid-crust whose rocks are cracked and filled with liquid water best explains both seismic and gravity data.”
An earlier paper concluded that closer to the surface, above a depth of about three miles, the upper crust did not contain water ice, as Manga and others had suspected. That may mean there is little accessible frozen groundwater outside the polar regions.