Mars orbiter finds first evidence of ancient, giant water lakes under planet

28 Feb 2019

Image: © helen_f/

An ESA spacecraft has detected strong evidence that beneath Mars there was once a series of vast interconnected groundwater lakes.

New findings revealed by the European Space Agency (ESA) Mars Express orbiter show why you should never judge a book by its cover. While now an arid, desolate planet with no signs of life (yet), scientists have found geological evidence to show that at some point there was a system of ancient interconnected lakes underneath the surface of Mars.

Not only that, but the researchers behind the discovery, writing in the Journal of Geophysical Research, revealed that five of these dead lakes beneath the planet’s surface may have contained minerals crucial to the development of life.

Building on previous discoveries – including branching flow channels and valleys, as well as the detection of a pool of liquid water beneath Mars’s south pole – the researchers wanted to see if models that had predicted such vast lakes were true.

Using the Mars Express orbiter, the researchers explored 24 deep, enclosed craters in the planet’s northern hemisphere, with floors lying roughly 4,000 metres below the planet’s arbitrary definition of ‘sea level’.

This led to the discovery of features on the floors of these craters that could have only formed in the presence of water, most likely pools and flows that changed and receded over time. Other features include channels etched into crater walls, valleys carved out by sapping groundwater, as well as dark, curved deltas thought to have formed as water levels rose and fell.

These water levels also appear to align with the proposed shorelines of what would have been Mars’s ocean, thought to have existed between 3bn and 4bn years ago.

Infrared satellite map of the waterways and ancient lakes beneath Mars.

This image shows the distribution of a number of deep craters (marked as dots) recently explored as part of a study into groundwater on Mars. Image: Topography: NASA/MGS/MOLA; Crater distribution: F Salese et al (2019)

‘Contemporaries of a Martian ocean’

“We think that this ocean may have connected to a system of underground lakes that spread across the entire planet,” said co-author Gian Gabriele Ori.

“These lakes would have existed around 3.5bn years ago, so may have been contemporaries of a Martian ocean.”

The five craters that really caught the researchers’ attention contained minerals essential to the birth of life, including various clays, carbonates and silicates. These were the only basins deep enough to intersect with the water-saturated part of Mars’s crust for long periods of time.

ESA Mars Express project scientist Dmitri Titov said: “Findings like this are hugely important; they help us to identify the regions of Mars that are the most promising for finding signs of past life.

“It is especially exciting that a mission that has been so fruitful at the Red Planet, Mars Express, is now instrumental in helping future missions such as ExoMars explore the planet in a different way.”

Colm Gorey was a senior journalist with Silicon Republic