The water on Mars appears to have been an especially good home for life, according to a new study.
Mars is one of the most likely possible homes for alien life in our solar system, and water is thought to be a key requirement for that life to take hold.
Previous studies have suggested the red planet would once have been home to lakes of flowing water, that could have been home to life.
But there has still been no evidence to suggest that alien life once lived on the planet – or that there is any evidence of it there still.
In an attempt to understand what the ancient Mars could have looked like and whether it was inhabited, scientists have looked to understand the water chemistry that would have been found on the planet billions of years ago.
They do so by looking at the materials left over on the planet today, which could offer a clue to how it once looked.
Recent measurements taken by Nasa's Curiosity rover on the Martian surface suggest that the water that is thought to have once covered its surface could have had just the right ingredients to support any microbial life that formed on the planet.
The new study looked at sediments that seemed to have been left in lakes on Mars's Gale Crater. It found they appeared to have formed in the presence of liquid water that had a similar pH to that in Earth's oceans.
That suggests that the early surface of Mars would have been the kind of place that could have served as a home for life, like that on Earth.
A paper detailing the discovery, titled 'Semiarid climate and hyposaline lake on early Mars inferred from reconstructed water chemistry at Gale', was published in Nature Communications.