Gullies on Mars may have been formed by recent periods of melted liquid water, study finds

June 30 () –

A study led by researchers at Brown University (United States) offers new insights into how water from melting ice may have played a recent role in the formation of gully-like channels that cut the sides of impact craters in Mars.

The study, published in the journal Science, focuses on Martian gullies, which look eerily similar to gullies that form on Earth in the Dry Valleys of Antarctica and that they are caused by the erosion of the water coming from the melting of the glaciers.

The researchers, including Jim Head, a planetary scientist at Brown, built a model that simulates a sweet spot at which conditions on Mars allow the planet to warm above freezing temperatures, resulting in periods of liquid water on Mars when ice above and below the surface melts.

They discovered that when Mars is tilted on its axis by as much as 35 degrees, the atmosphere becomes thick enough for brief melting episodes to occur where there are gullies.

Next, they compared their model data to periods in Mars history when gullies in the planet’s Terra Sirenum region are thought to have expanded rapidly downslope from high points, a phenomenon that could not be explained without the occasional presence of water.

“We know from much of our research and that of others that early in the history of Mars there was running water on the surface with networks of valleys and lakes.“explains Head, a professor of geological sciences at Brown.

“But around 3 billion years ago, all that liquid water was lost and Mars became what we call a hyperarid or polar desert,” he adds. “Here we show that even after that and in the recent past, when the As the axis of Mars tilts 35 degrees, it heats up enough to melt snow and ice, returning liquid water until temperatures drop and it freezes again.”

The findings help fill in some of the missing gaps about how these ravines formed, including the height at which they begin, the severity of erosion, and how far down the slopes of the craters they extend.

According to previous theories, Martian gullies were formed by carbon dioxide frost evaporating from the ground, causing rocks and debris to slide down the slopes.

The height of the ravines led many scientists to theorize that meltwater from the glaciers had to be involved due to the distance they traveled down the slopes and the eroded appearance of the ravines. Proving the existence of liquid water on Mars since it disappeared so long ago has been difficult because temperatures often hover around 70 degrees below zero.

The results of the new study suggest that the gully formation was due to periods of snowmelt and frost evaporation of CO2 at other times of the year. According to the researchers, it is likely that this phenomenon has been repeated over the last few million years, the most recent being about 630,000 years ago.

They say that if there was ice in the gullies in the areas they studied when the axis of Mars tilted about 35 degrees, the conditions would have been right for the ice to melt because temperatures rose above 273 degrees Kelvin, equivalent to About zero degrees Celsius.

“Our study shows that the global distribution of gullies is best explained by liquid water over the last million years. says Jay Dickson, the study’s lead author and a former Brown researcher who is now at the California Institute of Technology. Water explains the elevation distribution of gullies in a way that CO2 cannot. This means that Mars has been able to create liquid water in sufficient volume to erode the channels in the last million years, which is very recent on the scale of the geological history of Mars.”

Despite doubts that meltwater was possible and scientists were never able to model the right conditions on Mars for ice to melt, the researchers were convinced the meltwater theory was accurate because they had seen similar features firsthand in Antarctica.

There, despite the low temperatures, the sun is able to heat the ice enough for it to melt and ravine activity to take place.

The new study is a continuation of previous research the team began decades ago on Martian ravines. In a 2015 study, for example, the researchers showed that there may have been periods on Mars in the past when water was available to form gullies if Mars tilted far enough on its axis.