What is believed to be liquid water is sitting below Mars’ southern polar ice cap and is described as a “well-defined, 20-kilometer-wide zone.” 20 kilometers is roughly 12.5 miles.The data comes from the ESA’s Mars Express orbiter, which carries a ground-penetrating radar instrument called MARSIS. It has generated roughly 13 years of data, including multiple passes over the polar regions. The interface between ice and water acts similarly, producing a bright reflection. Analysis of that data had already identified a highly reflective region beneath the thickest part of the southern ice cap in an area called the Planum Australe. A layer of pure water ice is expected to exist.
ESA Mars Orbiter
There are other possible explanations for this sort of signal, but the authors consider and reject them. The presence of liquid water at the bottom of the Martian polar ice caps was first theorized more than 30 years ago, the researchers said. The water is likely to be below the freezing point for water (32°F or 0°C). Despite the obvious excitement surrounding the findings, Mars’ surface is “inhospitable to life,” according to the Open University’s Dr. Manish Patel. But “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,” Dmitri Titov, ESA’s Mars Express project scientist, said.