Martian valleys studied reveal that the young red planet had a fairly icy landscape.

Today Mars is cold and dry. But that may not always have been the case. Scientists hypothesize that the red planet was warm and humid in the distant past, and water flowed liberally across the surface. A new study is now questioning this assumption. Because possibly the former Martian landscape did not consist of free flowing rivers, but of ice caps.

Water
It is no coincidence that scientists think that water-filled rivers once flowed abundantly over the surface of Mars. There are countless signs on Mars that indicate that large amounts of water once flowed across the planet. Think of undulating tracts visible from space, branches and river beds. But researchers now argue that many of the valleys carved into the landscape were not created by free-flowing rivers. Instead, they are cut into the surface by water melted under glacial ice. It means that the theory that Mars once had a warm and wet climate that caused rainfall, rivers, oceans to exist on the red planet must be strongly reconsidered.

Valleys
The researchers studied more than 10,000 Martian valleys in the new study. They then compared these valleys to the subglacial channels in the Canadian Arctic archipelago. And the team came across some notable similarities. As a result, the researchers now argue that the early Martian landscape probably resembled that of Devon Island in the Arctic Ocean. “In the past forty years, since the Martian valleys were first discovered, it was believed that flowing rivers were responsible for all of these valleys,” said researcher Grau Galofre. “But there are hundreds of valleys on Mars and they all look very different. If you look at the Earth with a satellite, you will also see many valleys. Some are created by rivers, others by glaciers or other processes. In addition, each valley looks slightly different. This is also the case on Mars. The valleys differ from each other, which suggests that many different processes have carved these valleys into the landscape. ”

Valleys on Mars (top) compared to channels on Devon Island (bottom). The shape and the entire network appear almost identical. Image: Anna Grau Galofre

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Using a new algorithm, the researchers managed to uncover the underlying erosion processes of the valleys studied. And the results are groundbreaking. “They provide the first evidence of subglacial erosion caused by the channeled meltwater runoff under an ancient ice sheet on Mars,” concluded researcher Mark Jellinek. In other words, the valleys may not have been created by rivers, but by ice caps. “The findings show that only a fraction of the valleys on Mars match the patterns associated with river erosion,” Jellinek explains. “This is in sharp contrast to the existing theories.”

Zone
The new hypothesis also sheds light on another existing mystery. Researchers have long wondered how it was possible that the valleys formed 3.8 billion years ago on a planet farther from the sun than Earth during a time when the sun was also less strong. The new study helps explain this. “Climate models predict that it was much colder on Mars when the valleys formed,” says Galofre. We have tried to reconcile everything and now propose a hypothesis that has not really been considered yet: the channels and valley networks can also arise under ice sheets as part of the drainage system that naturally forms under an ice sheet as water accumulates. ”

According to the researchers, these environments would also provide better survival conditions for possible past life on Mars. An ice layer offers more protection and stability for the underlying water. In addition, ice protects against solar radiation in the absence of a magnetic field – something Mars once had, but which disappeared billions of years ago. Whether there are traces of (former) life on the red planet can be found NASA’s newly-launched Mars rover will seek out Perseverance. Perseverance was successfully launched last Thursday and will land in the Jezero Crater (a 45-kilometer area just north of the Martian equator) in February 2021. Here the rover will actively search for traces of microbial life or even micro-organisms that may still be stored in deposits or sediments.