Scientists have found a cluster of three salty liquid water lakes on Mars, each about six miles across, below the planet’s south polar ice cap.
An international team examined radar data from MARSIS, a scientific instrument on board the European Space Agency’s Mars Express spacecraft.
The technique uses bursts of radio waves to image buried geological structures – in a similar fashion to ‘seismic prospecting’, which helps predict earthquakes.
They found the briny lakes – which have potential to sustain microbial life in extreme conditions – at Ultimi Scopuli, a region near the Red Planet’s south pole.
Microbial life in the lakes could include extremophiles, which can stand intense heat, highly acidic environments, extreme pressure and extreme cold.
The new discovery is the first ‘alien’ water found on the Red Planet since 2018, when the first ever lake was discovered beneath the Martian south polar ice cap.
The 2018 discovery was the first proof of liquid water on Mars that still exists today – an environment scientists say is ideal for the growth of microbial life.
Scientists say the new lakes in the same region are an indicator of ‘the presence of other wet areas nearby’.
Map generated using radar data with ‘reflective permittivity values’ larger than 15 suggesting the presence of liquid water. The central blue-filled isoline indicates the location of the lake found in 2018
‘The existence of a single sub-glacial lake could be attributed to exceptional conditions such as the presence of a volcano under the ice sheet,’ said Roberto Orosei, principal investigator of the MARSIS experiment.
‘[But] the discovery of an entire system of lakes implies that their formation process is relatively simple and common, and that these lakes have probably existed for much of Mars’ history.
‘For this reason, they could still retain traces of any life forms that could have evolved when Mars had a dense atmosphere, a milder climate and the presence of liquid water on the surface, similar to the early Earth.’
The three newly detected water bodies appear to be ‘discrete and not physically linked’, according to co author Dr Angelo Pio Rossi at Jacobs University in Bremen, Germany.
‘We could detect three bodies of water which are located around the main one already detected in 2018 paper, and are separated by strips of dry terrain,’ he told MailOnline.
The analysis presented in this work was performed on the data acquired in 134 radar profiles from Ultimi Scopuli. This image shows topographic map and location of MARSIS profiles collected in the region, with the new lakes indicated by diagonal red lines (top). The black star in the middle of the red cross indicates the centre of the area detected by Orosei et al in 2018
The new water bodies were found using data from the European Space Agency’s Mars Express probe, which has orbited the Red Planet since 2003 and began to collect data in the summer of 2005.
Researchers used the probe’s Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument to explore the planet’s polar ice caps.
The device sends radar signals that penetrate the ice at the planet’s surface, and measures how the radio waves spread and reflect back to the probe.
The methodology is commonly used in radar sounder investigations of sub-glacial lakes in Antarctica, Canada and Greenland.
Each of the three lakes are about 6.2 miles (10km) across and around 12 miles from the 2018 lake.
The 2018 discovery was the first proof of a liquid water on Mars that still exists today – an environment scientists say is ideal for the growth of microbial life. The lake is believed to sit below this patch of ice at the south pole
The new lakes are also about 0.9 miles (1.5km) in depth from the surface, which is not too different vertically compared to the depth of the 2018 lake.
‘But the actual depth, or thickness, of the water bodies cannot be measured with MARSIS sounding radar data (or any other radar) since the radar could not penetrate further,’ Dr Rossi told MailOnline.
‘What is measured is just the depth of the top of these liquid water bodies.’
Detection of sub-glacial liquid water in Ultimi Scopuli in 2018 reignited hopes of extra-terrestrial life in liquid water at the Martian polar regions.
MARSIS had detected an area of strong reflectivity beneath the South Polar Layered Deposits – a thick polar cap formed by layers of ice and dust.
This originally discovered lake is discovered to be about the size of lake Windermere, spanning 12 miles (20km) and buried nearly a mile (1.5km) underground.
Scientists at the Italian National Institute for Astrophysics in Rome uncovered the subsurface lake using data from the European Space Agency’s Mars Express probe (artist’s impression)
The announcement was followed by efforts to confirm the initial finding and to further understand the conditions that would allow liquid water to persist under the Martian south polar ice cap.
Now, old and new MARSIS data reveals the existence of this ‘patchwork’ of three lakes, although it’s not known if they are connected with the lake found in 2018.
‘Not only did we confirm the position, extent and strength of the reflector from our 2018 study but we found three new bright areas,’ said co-lead author Elena Pettinelli at Roma Tre University.
‘The main lake is surrounded by smaller bodies of liquid water, but because of the technical characteristics of the radar, and of its distance from the Martian surface, we cannot conclusively determine whether they are interconnected.’
As it stands, technologies do not allow for drills to penetrate deep enough to reach the liquid water in the lake, however.
Briny solutions such as the water on the Martian south pole remain in a liquid state on Earth at temperatures much lower than the freezing point of water.
Because of this, brines have been proposed as the most plausible form of liquid water on Mars, which has an average global temperature of around -108°F (-60°C).
This artist’s impression shows the Mars Express probe investigating the southern hemisphere of Mars over a radar cross section of the craft’s readings. The blue spots are areas of high reflectivity – thought to be liquid water
‘These experiments have demonstrated that brines can persist for geologically significant periods of time even at the temperatures typical of the Martian polar regions considerably below the freezing temperature of pure water,’ said study author Graziella Caprarelli at University of Southern Queensland.
‘Therefore we think that any process of formation and persistence of sub-ice water beneath the ice polar caps requires the liquid to have high salinity.’
Water bodies therefore represent areas of ‘potential astrobiological interest and planetary protection concern’, the experts say in Nature Astronomy.
‘Future missions to Mars should target this region to acquire experimental data in relation to the basal hydrologic system, its chemistry and traces of astrobiological activity.’
Finding more reservoirs of sub-glacial water and determining their composition and astrobiological potential is now the next stage of the research.
Scientists believe Mars holds large volumes of water but much of it is stored in ice or in brine patches
How important is the presence of liquid water?
It is now widely believed that Mars holds a reasonably large volume of water.
However, the surface of the planet is so cold, this water exists only as ice.
In order for life to exist on a planet, many scientists believe it is essential for the world to possess liquid water.
Ever since technology has enabled mankind to gaze at Mars in detail, humans have been looking for indications that there was water on the red planet.
Did water used to flow on the surface of Mars?
The Mariner 9 mission revealed clues of water erosion in river beds and canyons, as well as evidence of weather fronts and fogs on Mars in 1971.
Later missions from the Viking orbiters, which first launched in 1975, revealed yet more details about how water flowed on the surface and carved valleys.
Several studies investigated the presence of liquid water for decades. In 2000, the first proof of liquid water on Mars was discovered.
It was claimed the gullies seen on the surface of the planet had to have been formed by flowing water.
Scientists cited the debris and mud deposits left behind as evidence for moving water existing at some point in the history of the red planet.
However, the formation of these gullies has been hotly debated throughout the ensuing years.
Proof of ice in geological samples from Mars
Spirit and Opportunity, the twin rovers, found evidence of the presence of water enclosed in rock in 2007, when one of Spirit’s wheels broke and gorged a piece of stone.
Analysis of the silica-rich layer discovered in the scratch suggested it formed in the presence of liquid water.
In 2008, the Phoenix lander was gathering geological samples, and they disappeared after a few days.
Scientists thought these were pieces of ice. This assessment was confirmed when the lander later detected water vapour in a sample.
In 2012, Curiosity was meandering over an ancient martian seabed when it examined a number of rocks that were exposed to liquid water billions of years ago.
In 2012, Curiosity (pictured) was meandering over an ancient martian seabed when it examined a number of rocks that were exposed to liquid water billions of years ago
Recurring slope lineae and debate causes it
Features known as recurring slope lineae (RSL) were first identified in 2011.
These dark streaks populate the areas of Mars with a sharp incline.
Researchers speculated that these may have been caused by the intermittent flow of liquid water down steep banks on the planet.
In June 2013, Curiosity found powerful evidence that water good enough to drink once flowed on Mars. In September of the same year, the first scoop of soil analysed by Curiosity revealed that fine materials on the surface of the planet contain two per cent water by weight.
In 2015, Nasa claimed to have discovered the first evidence of liquid water on Mars in the present day.
The space agency said that its Mars Reconnaissance Orbiter (MRO) provided the strongest evidence yet that liquid water flows intermittently on present-day Mars.
In 2017, Nasa issued another statement rebuking its initial findings.
Features known as recurring slope lineae (RSL) were first identified in 2011 (pictured). These dark streaks populate the areas of Mars with a sharp incline. Researchers speculated that these may have been caused by the intermittent flow of liquid water
It said the dark features that run down steep inclines on the red planet were actually granular flows, where grains of sand and dust slip downhill to make dark streaks, rather than the ground being darkened by seeping water.
Images from the MRO revealed the streaks only exist on slopes steep enough for dry grains to descend the way they do on faces of active dunes.
Also in 2017, scientists provided the best estimates for water on Mars, claiming it once had more liquid H2O than the Arctic Ocean – and the planet kept these oceans for more than 1.5 billion years.
The findings suggest there was ample time and water for life on Mars to thrive, but over the last 3.7 billion years the red planet has lost 87 per cent of its water – leaving the surface barren and dry.
A subterranean lake
In a study published in the journal Science, ESO researchers have now discovered the first concrete evidence for liquid water on Mars.
Using radar imagery from the Mars Express probe, the ESO team have found a 12-mile long underground lake filled with liquid water.