On August 2018, scientists have submitted a study suggesting that a subterranean lake might be found on Mars. This theory came about as a team of researchers studied the radar data collected from the European Mars Express. In their analysis, they have identified a liquid mass resembling a saltwater lake about 20 kilometers (12.5 miles) wide and 1.5 kilometers (1 mile) below the surface. the lake is said to be found under the Red Planet's southern ice cap.

A new study has recently emerged concluding that an active groundwater system could possibly be found beneath the equatorial regions of Mars. This study gives an explanation to one of the mysterious phenomena that the Martian surface is exhibiting.

A theory by Abotalib Z. Abotalib and Essam Heggy, researchers from the University of Southern California, revolves around the recurring slope lineae (RSL) as a result of a deep reservoir of salty water which is presumed to be currently active. RSL is described as the dark streaks that periodically appear on the sides of the craters on the Martian landscape.

Nature Geoscience has published the study on Thursday where images provided the high-resolution camera on the Mars Reconnaissance Orbiter of the National Aeronautics and Space Administration (NASA) that has been orbiting Mars to survey the different features on the surface of the Red Planet.

In their research, Abotalib and Heggy analyzed photos of Palikir crater to arrive at their new hypothesis. The said crater has been harboring RSL. It is now seen as a prime location for present-day water flows.Heggy stated that the Red Planet is nor hydrologically dead. 

RSL has been the center of many studies of various groups over the past years. There are now a number of theories that were lobbied with regards to the occurrence of RSL. One of which was the idea that the streaks were a result of sand flows on the surface. Some suggested that the streaks were caused by the seeping saltwater that is just below the Martian surface but shallow pools of groundwater have not been found or identified in radar experiments.

The duo's different perspective on the Martian RSL came from their backgrounds in studying aquifers and groundwater flow in the different desert environments on Earth. The similarities between Earth and Mars fueled their paper. Their hypothesis is that water can be found at about 750 meters (about half a mile) into the surface of Mars. Due to the high pressure, the liquid is being forced up through the soil, finding its way through fractures and cracks on the surface.