Melting ice water may have contributed to gullies' formation on Mars, study finds

A recent study led by researchers from Brown University sheds new light on the formation of ravine-like channels, known as gullies, on Mars, suggesting that water from melting ice may have played a significant role.

Martian gullies bear a striking resemblance to gullies found in the Dry Valleys of Antarctica, formed by water erosion from melting glaciers. The research team, including Brown planetary scientist Jim Head, developed a model to simulate the conditions under which Mars could experience periods of above-freezing temperatures, leading to liquid water on the planet's surface.

The team discovered that when Mars tilts on its axis to approximately 35 degrees, its atmosphere becomes dense enough to allow brief episodes of melting at gully locations. By comparing their model's data with periods in Martian history when gullies in the Terra Sirenum region rapidly expanded downhill from higher elevation points, the researchers found that the presence of water was necessary to explain the phenomenon.

"We know from a lot of our research and other people's research that early on in Mars history, there was running water on the surface with valley networks and lakes. But about 3 billion years ago, all of that liquid water was lost, and Mars became what we call a hyper-arid or polar desert. We show here that even after that and in the recent past, when Mars' axis tilts to 35 degrees, it heats up sufficiently to melt snow and ice, bringing liquid water back until temperatures drop and it freezes again," said Jim Head, a professor of geological sciences at Brown.

Prior theories suggested that Martian gullies were carved by carbon dioxide frost, which evaporates from the soil. However, the height and erosion of the gullies led many scientists to hypothesize the involvement of meltwater from glaciers. Confirming the existence of liquid water on Mars has been challenging due to the planet's typically frigid temperatures, hovering around 70 degrees below freezing.

The new findings indicate that gully formation was driven by periods of melting ice, as well as by evaporation of carbon dioxide frost during other parts of the year. The researchers suggest that this process has likely occurred repeatedly over the past several million years, with the most recent occurrence approximately 630,000 years ago.

Despite doubts about the possibility of meltwater, the researchers were convinced that the theory of meltwater on Mars was accurate due to their firsthand observations of similar features in Antarctica.

Published in the journal Science, this study builds upon previous research conducted by the team, which began several decades ago, examining Martian gullies.

"Everybody's always looking for environments that could be conducive to not just the formation of life but the preservation and continuation of it. Any microorganism that might have evolved in early Mars is going to be in places where they can be comfortable in ice and then also comfortable or prosperous in liquid water. In the frigid Antarctic environment, for example, the few organisms that exist often occur in stasis, waiting for water," Head explained.