Life on Mars hopes raised as scientists reveal water was made up of ice sheets rather than flowing rivers, scientists say

Mars may once have been covered in ice sheets like those in the Arctic, rather than flowing rivers, according to a new study.

When the valleys that cross across Mars's surface were spotted and further explored, they led to hope that rivers once flowed across its surface. That helped contribute to the idea that the planet was once wet and warm, with rainfall and oceans.

But the water that previously existed on the planet might actually have been there in a similar way to the ice that formed similar channels in the Canadian Arctic Archipelago, according to the new study.

That could actually be more helpful to any alien life that might once have lived on the ancient Mars, the researchers say, since the ice sheets would offer protection, allowing the water underneath to stay stable as well as serving as a barrier against the solar radiation that is thought to have once bombarded the Martian surface.

Researchers examined thousands of Martian valleys, which allowed them to generate detailed information on their construction. They then compared those channels found on Mars's surface with those channels, helping to understand what conditions might have given rise to them.

They found that they looked remarkably similar, with only a small number of the valley networks appearing as if they had been formed by surface water erosion. Instead, they seem to have come about as a result of extensive erosion from water draining beneath an ancient ice sheet, they found.

"For the last 40 years, since Mars's valleys were first discovered, the assumption was that rivers once flowed on Mars, eroding and originating all of these valleys," said Grau Galofre, who led the research published in Nature Geoscience, in a statement.

"But there are hundreds of valleys on Mars, and they look very different from each other. If you look at Earth from a satellite you see a lot of valleys: some of them made by rivers, some made by glaciers, some made by other processes, and each type has a distinctive shape. Mars is similar, in that valleys look very different from each other, suggesting that many processes were at play to carve them."

The research would also help answer the mystery of how the valleys could have formed on a planet so far from the Sun, as well as so long ago, at a time when it was less intense.

"Climate modelling predicts that Mars' ancient climate was much cooler during the time of valley network formation," said Galofre. "We tried to put everything together and bring up a hypothesis that hadn't really been considered: that channels and valleys networks can form under ice sheets, as part of the drainage system that forms naturally under an ice sheet when there's water accumulated at the base."