In a new study, scientists have found new evidence that gullies on the slopes of Martian craters formed during periods of melting ice water on and beneath the planet’s surface. The study, led by scientists from Brown University, sheds light on the formation of gully-like channels that dissect the slopes of impact craters on Mars. The paper was published in the scientific journal Science
Drawing parallels between Martian gullies and gullies in Antarctica’s dry valleys, which form as a result of water erosion of melting glaciers, the scientists built a model that simulates the conditions under which liquid water could exist on Mars. They found that when Mars is tilted relative to its axis by 35 degrees, the atmosphere becomes dense enough that short-term episodes of melting occur in the locations of gullies.
According to Jim Head, a planetary scientist at Brown University, this study fills critical gaps in our understanding of how these gullies formed. “We know from previous studies that early in Mars’ history, flowing water existed on the surface in the form of networks of valleys and lakes,” he explains. “But about 3 billion years ago, all this liquid water was lost and Mars became what we call a hyper-arid or polar desert. We show that even after that and in the recent past, when Mars’ axis tilted 35 degrees, it warmed up enough to melt snow and ice, returning liquid water until the temperature dropped and it froze again.”
The findings disprove previous theories that Martian gullies were formed by frost vaporization of carbon dioxide, causing rocks and debris to slide down slopes. The height and erosion of the gullies indicate that glacial meltwater was involved in their creation. However, proving the existence of liquid water on Mars has been difficult because of the extremely low temperatures.
The researchers suggest that the formation of gullies on Mars occurred during periods of ice melt and evaporation of carbon dioxide. They believe that this process has occurred repeatedly over the past few million years, with the most recent occurrence taking place about 630,000 years ago. The authors of the study suggest that if ice was present at the gully sites when Mars’ axis tilted by about 35 degrees, conditions would have been ideal for it to melt, as temperatures would have risen above freezing.
This groundbreaking research not only deepens our understanding of Mars’ geologic history, but also raises intriguing questions about the possibility of life on the red planet in the past and present. As scientists continue to explore the mysteries of Mars, these results will undoubtedly be an important step in unlocking the secrets of the neighboring planet.