The Mars of the past could have had a thin layer of icy clouds that would have created a greenhouse effect that, in turn, would have allowed suitable conditions for the water to flow, being able to have lakes and rivers.
One of the great mysteries of modern space science
At that time when the red planet, currently a dusty desert with no clear signs of life, the Sun was much weaker than it is today and Mars receives a third of the amount of sunlight that we enjoy today on Earth. . However, a new study led by University of Chicago planetary scientist Edwin Kite, assistant professor of geophysical sciences and an expert on otherworldly climates, has used a computer model to present this promising explanation.
“There has been an embarrassing disconnect between our evidence and our ability to explain it in terms of physics and chemistry,” Kite said . “This hypothesis goes a long way toward closing that gap.”
Of the many explanations that scientists have come up with on various occasions, none of them fit entirely: from a collision of a large asteroid that could have released enough kinetic energy to warm the planet to other theories that, likewise, did not work as they should.
How did Mars retain its water?
Thus, the 3D computer model of its atmosphere of how it would have been more than 3 billion years ago, revealed that it would have had a series of wispy high-altitude clouds similar to the contrails of aircraft. These cloud-like plumes originate where freezing temperatures freeze the water droplets before they have a chance to evaporate. A greenhouse effect similar to carbon dioxide in the atmosphere.
The idea was first proposed in 2013, but largely shelved because, “it was argued that it would only work if the clouds had implausible properties,” Kite clarifies. For example, the models suggested that water would have to stay in the atmosphere for a long time, much longer than it usually does on Earth, so the whole prospect seemed unlikely. But the missing piece was the amount of water on the ground. If ice were covering large portions of Mars, it would create surface moisture that would favor low-lying clouds, which are not believed to make the planets very hot (or even cool them, because clouds reflect sunlight away from the planet. ).
But if there are only patches of ice, such as at the poles and on mountain tops, the air on the ground becomes much drier . These conditions favor high cloud cover, clouds that tend to heat planets more easily.
“In the model, these clouds behave in a very different way than on Earth,” Kite continues. “Building models based on Earth’s intuition just won’t work, because this is not at all similar to Earth’s water cycle, which moves water rapidly between the atmosphere and the surface.”
“Our model suggests that once the water moved into the early Martian atmosphere, it would stay there for quite a long time, closer to a year, and that creates the conditions for long-lasting high-altitude clouds,” explains the expert.
Mars is important because it is the only planet we know of that had the ability to support life and then lost it, so scientists hope that the Perseverance rover will test this hypothesis by analyzing rocks in order to reconstruct past atmospheric pressure on Mars.
Referencia: Edwin S. Kite el al., “Warm early Mars surface enabled by high-altitude water ice clouds,” PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.2101959118
