Mars has a massive, liquid water ocean, according to new analysis of data from NASA's retired InSight lander. InSight was launched in 2018, with a mission to record seismic activity on the Red Planet and quickly detected that Mars was still alive.
The new analysis is yet another piece of evidence to suggest that water wasn't vaporized when the planet lost its atmosphere billions of years ago, or that water is confined to the polar ice caps. But accessing the water is practically impossible.
Instead of being a surface ocean, the water is distributed throughout layers of rock, starting at least 11 kilometers (6.8 miles) beneath the planet's crust.
Calculations made by researchers from the University of California San Diego and Berkeley estimate there's enough liquid water infused through the rock to create a planet-wide ocean spanning two kilometers in depth.
But with no drill capable of burrowing that far on Earth, there's little hope of achieving the feat on Mars.
Using InSight's seismic data to detect water
In the absence of technology to drill deep into Mars's mantle, the scientists said they analyzed wave data to understand the composition of the planet's crust and the material held inside.
That data was collected by the Mars InSight lander during its four-year mission, which ended in December 2022.
Among its data collection were recordings of so-called 'Mars Quakes' and meteor impacts that cause surface motion on the planet and InSight recorded the speed that seismic waves travel during these events.
The research group used rock physics models to calculate the properties of Mars' crust when these fast-travelling waves pass through.
"The goal is to connect what's inside the rock to the speed of sound," said Vashan Wright, a geophysicist from UC San Diego's Scripps Institution of Oceanography, who led the analysis. "The more dense the rock, the faster the speed of sound will go in. You add in some liquid water, the speed will go up. If you crack it, the speed will go down."
Rather than expecting to find liquid water beneath the surface, Wright and colleagues took an "agnostic" approach to their search — expecting to find anything from 0% to 100% water, or water spread throughout rock layers.
The InSight data suggests that any water on Mars in its ancient past moved underground, forming an aquifer, much like groundwater on Earth.
"There are deep and long-standing questions on Mars, that [this study] helps us answer — it gives us clues into a water cycle that is unaffected by humans," Wright says.
Where there's water, is there life?
Wright's group is not the first to find the potential for liquid water to exist on Mars.
In 2022, Caltech researchers used the Mars Reconnaissance Orbiter to study salt deposits on the planet's surface, estimating that water persisted until as recently as two billion years ago.
Studies of the northern polar ice cap had also suggested liquid water might exist beneath the frigid surface, but a recent investigation quelled those findings as a possible misinterpretation of radar measurements.
A decade ago, NASA studies showed water may occasionally flow on the planet's surface.
That's exciting for scientists still searching for evidence of life on Mars. As on Earth, liquid water is considered an essential ingredient to allow life to evolve.
"Water seems to be essential for life," Wright says. "What we know about life and water at depth is that on Earth you have life surviving in very 'harsher' conditions than it is at the surface. If you find water deep down, it does not mean life, but it means the possibility exists."
