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Billions of years ago, rain once fell on the Martian plain, and not always gently.
New research into the now empty lakes of the Red Planet suggests that an enormous amount of liquid water must have escaped the sky around 3.5 to 4 billion years ago, enough to carve channels into shape. river and pierce several lake basins.
“This is extremely important because 3.5 to 4 billion years ago, Mars was covered with water. There was a lot of rain or snowmelt to fill these channels and lakes”, explains the planet. Gaia Stucky of Quay at the University of Texas.
Modeling what the climate of Mars looked like all those years ago is incredibly difficult, but studies of the planet’s geomorphology and chemistry certainly suggest that it was once home to an abundance of water, fed both by precipitation. and melting snow.
Scientists don’t know how long these showers lasted or whether the weather was torrential, drizzle, or a mixture, but markings on the surface of Mars suggest there were once showers heavy enough to leave a lasting impression.
“Now it’s completely dry,” says Stucky of Quay.
“We’re trying to figure out how much water was there and where it all went.”
Using satellite imagery and topography, the researchers examined 96 lake basins on Mars that would have formed all these billions of years ago. Some of the basins had ruptured due to the water overflows, known as open basins, while others remain intact, called closed basins.
By measuring these lakes and their watersheds, the team was able to show how much precipitation and snowmelt would have been required to fill intact basins without piercing them, while simultaneously overflowing open basins.
In cases where a closed and open basin was fed by the same river, the researchers could predict both the maximum and minimum precipitation that might have fallen in a single event.
In a single rainstorm, which could have lasted for days or even thousands of years, researchers estimate that precipitation on Mars fell to between 4 and 159 meters (13 and 520 feet).
While the effects can be seen globally, not all areas have been affected in the same way. Some open-basin lakes were in areas considered to be “semi-arid” on Earth, so they likely received less water than wetter parts.
“We re-emphasize that our constraints are based on a threshold – not cumulative – event (i.e., lake overflow) that must have occurred during a single, near-continuous runoff event, which may have recurred multiple times, ”the authors write.
“Indeed, the large erosion volumes of the entrance valleys require cumulative volumes of water which generally exceed the volumes of the lake basins, thus suggesting repeated runoff episodes …”
In other words, the deeper channels leading to the lakes were probably dug during several showers, which would probably have flooded the lakes several times.
Recently, however, some scientists have suggested that these valleys weren’t just carved out by water, and by overestimating the impact of precipitation, we could miscalculate the precipitation itself.
Still, the authors believe this new knowledge about precipitation and aridity could help improve and test our climate models for the Red Planet, but they admit that their results are only one piece of the bigger puzzle.
Understanding the evolution of Mars’ climate will be key to assessing its potential to harbor life, and that is why the Mars 2020 Perseverance rover is currently heading towards a lake bed.
The study was published in Geology.
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