Mars had its own Mediterranean Sea: researchers found evidence of Earth-like processes on the Red Planet (photo).

One of the greatest mysteries is what the ancient climate of Mars was like. Once, the planet was wet and warm; now, it is dry and cold. However, the climatic changes on Mars were not abrupt. New research indicates that on ancient cold Mars, layers of frozen carbon dioxide allowed rivers to flow and a sea the size of the Mediterranean to exist. In Earth's cold climate, rivers can flow beneath thick protective ice covers. Scientists believe something similar occurred on Mars. The study is published in the journal JGR Planets, reports Universe Today.

The researchers utilized extensive data gathered during the study of Mars to create a model of how water behaved on the Red Planet as it became cold and dry.

Scientists suggest that 3.6 billion years ago, most of the water on Mars's surface was already frozen in large ice sheets in the planet's southern region. The atmosphere of Mars, composed of carbon dioxide, underwent periodic changes, leading to the formation of a massive ice cap of frozen carbon dioxide at Mars's south pole. However, at the same time, liquid water remained beneath the ice sheets.

The scientists' model demonstrates that the carbon dioxide ice cap acted as a thermal blanket and released a vast amount of meltwater. This water flowed through rivers, similar to how water on Earth drains from glaciers.

Researchers believe that so much water flowed out that it was sufficient to fill the Argyre Planitia on Mars. This is one of the largest impact basins on the Red Planet, with a diameter of approximately 1,800 km. This enormous impact basin was formed billions of years ago as a result of an asteroid collision. It lies about 5.2 km below the surrounding plains, making it the second-deepest impact basin on Mars. Scientists think that the Argyre Planitia contained as much water as the Mediterranean Sea on Earth.

According to the study's authors, rivers flowed beneath the ice, where they were insulated from the cold. When they emerged from the glacier, they seeped until a thick enough ice cap formed to insulate them. The ice grew until it reached thicknesses of hundreds of meters, while the water flowing beneath the ice caps was several meters deep. The water carved river channels thousands of kilometers long, with several of them extending from the polar cap to the Argyre Planitia.

The model indicates that filling the impact basin with water took about 10,000 years, and after it filled, the water poured out onto the surrounding plains over a radius of approximately 5,000 km. This process occurred repeatedly over an era spanning 100 million years, with each event separated by millions of years, scientists believe.