An artist's impression of the Mars Express spacecraft probing the southern hemisphere of the planet.
He noted that a higher-frequency radar instrument made by the Italian space agency, SHARAD, on board the Mars Reconnaissance Orbiter launched in 2005, has been unable to detect subsurface water.
Liquid water hanging out beneath the planet's surface, which is too hot for it to survive, has been a suspected reality for years.
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. A tool onboard the spacecraft sends radar pulses that penetrate the surface and ice caps of the planet and reflections off subsurface features provide scientists with information about what lies below.
Although the temperature of the lake is expected to be below the freezing point of pure water, the research team notes that salts of magnesium, calcium and sodium - known to be present in Martian rocks - could be dissolved in the water to form a brine.
Until now evidence from the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument, MARSIS, the first radar sounder ever to orbit another planet, remained inconclusive.
Still, she said, there are microbes on Earth that have been able to adapt to environments like that.More news: Greece wildfires: At least 20 killed near Athens as residents flee homes
The scientists analyzed radar profiles, within a 200 km-wide area, collected between May 2012 and December 2015. It's terribly cold on Mars, particularly at the poles, but the ice creates an insulating layer so that temperatures further down can actually be warmer.
After ruling out other explanations, they believe that the signals could reveal a patch of liquid water, more than 12 miles across and about a mile beneath the ice.
There is another satellite orbiting Mars right now, but it hasn't detected what MARSIS did. The bright horizontal feature at the top represents the icy surface of Mars in this region. A particularly bright radar reflection underneath the layered deposits is identified within a 20 km-wide zone. Image credit: NASA / Viking / JPL-Caltech / Arizona State University / ESA / ASI / University of Rome / R. Orosei et al.
Based on the report, the idea of water at the base of Mars' ice caps has been the subject of debate for over three decades.
"This subsurface anomaly on Mars has radar properties matching water or water-rich sediments", said MARSIS principal investigator Dr. Roberto Orosei, a researcher at the Istituto di Radioastronomia, Istituto Nazionale di Astrofisica, Bologna, Italy. Still, this sounds very promising, and it's exciting to think of the possibilities of what else might be up there. "This thrilling discovery is a highlight for planetary science and will contribute to our understanding of the evolution of Mars, the history of water on our neighbor planet and its habitability".