Image shows Mars 4 billion years ago revealing OCEAN world – and scientists say ‘lost' sea may still be hiding on planet

The Sun

12-05-2025

Sean Keach, Head of Technology and Science
Published: Invalid Date,
A LOST Martian ocean may be hiding beneath the red planet's surface.
Today Mars is a cold and dry desert – but it may have been covered in rivers, lakes, and seas around four billion years ago.
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Even as recently as 3.1 billion years ago, it may have still had "shimmering" liquid water in large quantities.
Scientists say that some of this escaped to space or froze on the polar caps – as well as the water that was trapped in minerals.
But scientists say that a there is still a significant amount of "missing" water that may be lurking under the ground.
In fact, this missing water is enough to cover the entire planet in an ocean "at least 700 metres deep, and perhaps up to 900 metres deep", according to Professor Hrvoje Tkalčić, of the Australian National University.
The scientists have used seismic data from Nasa 's InSight probe, which launched in 2018.
And this may have revealed a vast ocean underground.
"We uncovered evidence that the seismic waves slow down in a layer between 5.4 and 8 kilometres below the surface," Tkalčić explained.
"Which could be because of the presence of liquid water at these depths."
Nasa's InSight uses a seismometer to "listen" to the inside of Mars.
And scientists were able to track down a "significant underground anomaly".
This was a layer where the vibrations were moving more slowly – a "low-velocity layer".
The scientists believe this is very porous rock that has filled up with liquid water – just like a spone.
"We calculated the 'aquifer layer' on Mars could hold enough water to cover the planet in a global ocean 520–780m deep," said Tkalčić.
"Several times as much water as is held in Antarctica's ice sheet."
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The downside is that the seismic data only covers a small slice of Mars.
So scientists will need to get more seismometers to the red planet to fully map these potential water layers.
If they can find these water layers and drill into them, it could lead to a major breakthrough in the hunt for alien life.
"Liquid water is essential for life as we know it. On Earth, microbes thrive in deep, water-filled rock," Tkalčić explained.
"Could similar life, perhaps relics of ancient Martian ecosystems, persist in these reservoirs? There's only one way to find out.
Tkalčić continued: "The water may be a lifeline for more complex organisms, too – such as future human explorers.
"Purified, it could provide drinking water, oxygen, or fuel for rockets.
"Of course, drilling kilometres deep on a distant planet is a daunting challenge."
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MARS – WHAT YOU NEED TO KNOW
Here's a quick guide to Mars...
Mars is the fourth planet from the Sun, and Earth's space neighbour.
The blood-red planet was named by the ancient Romans after their god of war.
It's about 2,100 miles wide and roughly half the size of Earth.
The planet is around 142 million miles from the Sun on average, with sunlight taking 13 minutes to reach the red planet's surface.
A single Martian day lasts about 24.6 hours – while a year lasts 669.6 sols, or 687 Earth days.
The planet has two small moons named Phobos and Deimos.
It's home to Olympus Mons, which is the largest volcano in our solar system and around three times the height of Mt Everest.
Temperatures can range from 20C to -153C.
Picture Credit: Nasa / Reuters
Scientists think that this lost water could account for the "missing" water on the planet.
It may have ended up underground by seeping through cracks in the crust.
Those cracks may have been formed after Mars was "heavily bombarded by meteorites".
"Deep beneath the surface, warmer temperatures would keep the water in a liquid state – unlike the frozen layers nearer the surface," Tkalčić explained.
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This research was published in the National Science Review, and authored by scientists from the Chinese Academy of Sciences, Australian National University, and University of Milano-Bicocca.