Mars may have more water than scientists thought

Data showed that there are subsurface lakes on Mars back in 2018. That data came from an ESA spacecraft called Mars Express. The spacecraft shot radar signals at the surface of the Red Planet, and the data gathered showed that the South Pole of the planet appeared to have liquid subsurface Lakes. Since 2018, follow-up studies have revealed what are believed to be additional subsurface lakes on Mars.

A new paper was recently published by a pair of scientists from the NASA Jet Propulsion Laboratory. The paper describes finding dozens of similar radar reflections around the South Pole. The researchers analyzed a broader set of data collected by Mars Express. However, one discovery the data has revealed is puzzling. Scientists say that many of the radar reflections indicating water under the surface are in areas that should be too cold for water to remain in a liquid state.

JPL scientist Jeffrey Plaut says whether or not the signals are liquid water is a mystery, but scientists know that the signals appear to be much more widespread than what the original study found. Plaut says either liquid water is common beneath the South Pole of Mars, or the signals are indicating something else. Originally, the radar signals interpreted as subsurface water were found in a region of Mars known as the South Polar Layered Deposits.

That region gets its name from the alternating layers of water ice, dry ice, and dust that have settled there over the millennia. This particular area is of very high interest to scientists as they believe the layers provide a record of how the tilt in the axis of Mars has changed over time. Researchers beam radio waves at the planet's surface, which allow them to peer below the icy layers and map them in detail.

Radio waves lose energy as they travel through the material in the subsurface and are reflected back to the spacecraft as a weakened signal. However, in some cases, signals returning from the region suspected of having subsurface water were brighter than those at the surface. Those signals were interpreted to imply the presence of liquid water because water is known to reflect radio waves strongly. Plaut says the mapping gets scientists a few steps closer to understanding the extent and the cause of the mysterious radar reflections.