Mars Getting Better

The long-held belief that ancient Mars was an eternally cold and icy world may soon be shattered.  The latest research, published in the Journal of Geophysical Research: Planets, puts forward a bold hypothesis: billions of years ago, the Red Planet experienced periods of heavy rain and snowfall, and its climate was much closer to Earth's than previously thought. The discovery overturns decades of scientific understanding and forces a new look at the history of Mars.

For four years, NASA's Perseverance rover has been carefully exploring the Jezero Crater, a unique landscape where scientists believe a powerful river once flowed, forming a vast delta. However, the very existence of such a powerful water system is puzzling: how could a planet considered eternally cold provide such an intensive water supply?

Geologists from the University of Colorado Boulder, led by Dr. Amanda Steckel, decided to figure out this paradox. They created a digital climate model of Mars that simulated different scenarios. In some cases, the model included heavy rains and snowfalls, while in others, it relied solely on the melting of polar ice. The question was: could Mars, at least temporarily, have a climate similar to Earth? The results of the modeling were unexpected. When rain and snowfall were added to the model, river valleys and channels formed across the entire surface of the planet - at different latitudes and altitudes.

This perfectly matched the real Martian landscapes. In contrast, the scenario with a single source of water — melting glaciers — gave a completely different picture: water networks were concentrated only in high-mountain regions near the poles, which clearly did not match the observed reality. Having compared the results with photographs from NASA satellites, scientists confirmed that the relief of Mars is much more consistent with the impact of rain and snow, rather than the slow melting of ice.

But what about today's Mars, where snow falls only in the Polar Regions? It turns out that technology has already recorded snowfall. For example, the Mars Climate Sounder on the Mars Reconnaissance Orbiter satellite detected "dry ice" (frozen CO₂) falling to the surface. Back in 2008, the Phoenix mission used laser equipment to detect water snow near the North Pole. The only problem is that clouds often hide snowfall from spacecraft cameras, so direct visual evidence is rare.

 However, even the available data allows scientists to assert that snow on Mars is not only possible, but may have been quite common in the past. But the main mystery remains. How did Mars manage to maintain a warm climate in the era when the Sun was 25 per cent weaker than today (and this is about 4 billion years ago)? After all, for stable rains and rivers, a dense atmosphere and a powerful greenhouse effect are needed. 

According to geologist Brian Hynek , one of the authors of the study, many forms of Martian relief simply cannot be explained without a constant water flow. As an example, he cites the delta of the Jezero crater: a huge, scattered layer of sedimentary rocks there could only have formed with powerful and long-term river floods, and therefore in the presence of huge water masses. A new study finally destroys the myth of an eternally cold Mars. There is every reason to believe that in the distant past, the Red Planet was much more like Earth - with rivers, lakes, rain and snow. 

- pravda.ru