The Italian Space Agency believes it's found a 20km wide underground lake of liquid water locked under thick ice near the planet's south pole.
Orosei and co. used MARSIS to measure a section of Mars' canyon-filled southern ice cap called Planum Australe, which had been returning abnormal radar readings for a section of land in that area, between May 2012 and December 2015. Orosei estimated the water temperature at somewhere between 14 degrees Fahrenheit (minus 10 degrees Celsius) and minus 94 degrees Fahrenheit (minus 70 degrees Celsius).
The water is likely to be below the freezing point for water (32°F or 0°C) given its location beneath the ice cap, but the presence of minerals such as magnesium, calcium and sodium perchlorate in the soil of the northern plains of Mars, "support the presence of liquid water at the base of the polar deposits". That's because the radar works best at night and when it's within 500 miles of the planet's surface.
Scientists aren't even exactly sure what to call the body of water, which they detected by analyzing radar echoes gathered over three years by the orbiting Mars Express spacecraft.
It's not clear where the water the Italian team found is coming from, and it's not certain there are any other underground lakes to be found.
So the researchers did a rough calibration by registering the signal that bounced back when the radar hit the atmosphere/dusty ice boundary at the Martian surface, since the composition of these materials is pretty well understood.More news: Egypt's Mohamed Salah nominated for Federation Internationale de Football Association best player award
"This is the first body of water it has detected, so it is very exciting", David Stillman, a senior research scientist in the Department of Space Studies at Southwest Research Institute in Texas, told AFP in an email. The pressure also changes the melting point of water.
A few years ago, biologists found more than 3,500 unique gene sequences in Lake Vostok which had been isolated for more than 15 million years; Lake Vostok gets no sunlight with it being 4,000 metres below the ice and has a recorded temperature of -89.2c, showing life to be hardy.
For as long as anyone can remember, Mars was the planet that scientists, astronomers and stargazers looked to and wondered 'is there life out there?'.
One of the 29 samples showed unusually strong reflections.
"If there is microbial life operating there, it's operating under conditions that would be at the very limits of what we know life operates under here on Earth", said Brent Christner, a microbiologist at the University of Florida.
He suspects Mars may contain other hidden bodies of water, waiting to be discovered.
"Water is considered one of the fundamental requirements for life". And unfortunately, we don't have that understanding-the instrument was simply too large to open it up and calibrate it on the ground before Mars Express was launched.