It seems that scientists just can’t get enough of Mars at the moment. Fresh off the back of the discovery of salty water on its surface, new research suggests that lakes may have once been present – specifically at the Gale Crater, the location of the Curiosity rover.

Although lakes have been theorized before, based on data from orbit, Curiosity has been able to perform direct observations on the ground. It has been studying the geology of Gale Crater, 140 kilometers (90 miles) wide, which has a vast mountain known as Aeolis Mons, or Mount Sharp, that towers five kilometers (three mile) high at its center.

A new paper in the journal Science suggests that large impact craters like Gale were capable of storing water for thousands of years in the Martian past. The theory is based on studying clinoforms, the ordering of sediments on the bed of the ancient lake. The paper suggests that the surface of the crater basin rose over time, caused by the deposit of sediment. Some of this would have come from the northern crater wall, where gravel and sand were moved south in shallow streams. And eventually, wind-driven erosion dumped deposits in the center of the crater, forming Mount Sharp.

“This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin,” the researchers wrote in the paper.

^{Layers of rock on Mars (strata), seen by Curiosity. NASA/JPL-Caltech/MSSS.}

The layering of rocks suggests Gale Crater began with rivers, transporting sediment, before progressing to a standing body of water – a lake – at some point. This is based on analysis of sedimentary layers in the rock at Curiosity’s location, which are 75 meters (245 feet) thick.

The exact time the lake would have existed is not clear, although the sediment is thought to have been deposited between 3.6 and 3.2 billion years ago. The water table beneath the ground, where water was stored, would have been tens of meters deep, and while the extent of liquid water on Mars is not known, it’s possible this lake was linked to others by a groundwater table.

Woodward Fischer from Caltech, a co-author on the study, told IFLScience that the lake wouldn’t have been "especially deep, maybe a couple of meters to a couple tens of meters." He added that previous research had hinted at a lake in Gale Crater before, but those prior reports were "just little snippets that were tricky to place into a unique history." This latest study provides the best data yet on Gale Crater's lake.

As more and more evidence for water is found, it increases the chances that Mars once was – or still is – habitable to extraterrestrial life, Marjorie Chan of Utah University writes in Science. Considering how Earth-like some of these bodies of water may have been, it’s possible they could have once played host to some form of primitive life.