While it's always been known that the planet has substantial ice deposits, this is the first time scientists have detected a stable body of water in liquid form on the planet. Scientists in the past have discovered ice on the planet, pointing to the logical conclusion that life could, if not did, exist there.
The Italian team of researchers suspect the water is salty, or briny, which keeps it in liquid form. Its waters are likely so salty that they remain liquid despite the frigid -90˚ F conditions at the bottom.
While its existence provides a tantalising prospect for those interested in the possibility of past or present life on Mars, the lake's characteristics must first be verified by further research.
If other reservoirs are detected and a network of glacial lakes is uncovered - like on Earth - then it could indicate that water has persisted on Mars for millions of years, said Orosei. Water is considered a fundamental ingredient for life. Such migrations raise the possibility of the same thing happening on Mars - as the water retreated, life moved deeper underground.
"I've been studying life in ice for 35 years", he said.
Mars may have been a watery and temperate place in the distant past, but it's been a giant dustball for many eons. InSight is also the first mission dedicated exclusively to learning more about the planet's interior in an attempt to glean clues about how rocky terrestrial planets like Earth formed during the birth of the solar system 4.5 billion years ago.
Jeffrey Plaut of NASA's Jet Propulsion Laboratory said in an email that the interpretation that it is liquid water is "certainly plausible, but it's not quite a slam dunk yet". If astronauts ever crunch across the red sands will they also be crunching over fossils of microbes? "However, MARSIS can not say anything more".
Roberto Orosei, principal investigator of the MARSIS experiment and lead author of the paper said, "This subsurface anomaly on Mars has radar properties matching water or water-rich sediments", in an ESA statement. That is tens of billions of gallons.
Evidence for the Red Planet's watery past is prevalent across its surface in the form of vast dried-out river valley networks and enormous outflow channels clearly imaged by orbiting spacecraft. But the scientists figured out how to send back the raw data to Earth. But that feature had been ascribed to a boundary between the dust-containing ice that dominates Mars' surface and a layer of pure water ice that is expected to exist below that. That suggests that the water is brim full of salts, allowing it to melt.
"Water tends to collect in lower topography", Orosei said. Subsurface echo power is color coded and deep blue corresponds to the strongest reflections, which are interpreted as being caused by the presence of water. A particularly bright radar reflection underneath the layered deposits is identified within a 20-km-wide zone.
What they believe to be a lake sits under the planet's south polar ice cap, and is about 20km across. "You have a lot of interfaces that could do odd things to radar signals", said Zurek, who was not involved with the research.
For decades now, we've been searching for water on Mars. "That's the hard part".
After years of speculation, researchers have finally discovered liquid water on Mars. "It may exceed the salt content that any terrestrial organisms that we know of can survive in".
The body of water is about 20 kilometres across and, if confirmed, would be the first evidence of permanent water on the Red Planet. SHARAD operates at different frequencies than MARSIS does, but it's also created to pick up subsurface features. The team then spent nearly a year analyzing the data, and another two years writing their paper and attempting to rule out non-aqueous explanations for what they had seen. "They're eating the rocks for energy".