Madrid, 26 (Europe Press)
The presence of ice clouds at high altitudes would have kept Mars warm enough for rivers and lakes.
It is the result of a new study published in PNAS by planetary scientist Edwin Kate of the University of Chicago, associate professor of geophysical sciences and an expert on otherworldly climates.
Obviously, one of the great mysteries of modern space science is the rendering of NASA’s persevering spacecraft, which just landed on Mars, and is today a desert planet, yet the craft is floating next to an ancient river delta. This apparent contradiction has perplexed scientists for decades, especially since at the same time that Mars was bursting rivers, it received less than a third of the sunlight we enjoy on Earth.
Kate used a computer model to come up with a promising explanation: Mars may have had a thin layer of ice clouds at high altitudes that caused global warming. “There was an embarrassing disconnect between our tests and our ability to explain them in terms of physics and chemistry,” Kate says. “This hypothesis goes a long way toward closing this gap.”
Of the many explanations scientists previously suggested, none have fully succeeded. For example, some have suggested that a massive asteroid collision may have released enough kinetic energy to warm the planet. But other calculations show that this effect will only last for a year or two, and traces of ancient rivers and lakes show that warming has continued for hundreds of years at least.
Kate and colleagues wanted to review an alternative explanation: high-altitude clouds, like thin clouds on the ground. Even a small amount of clouds in the atmosphere can greatly increase the temperature of a planet, a greenhouse effect similar to that of carbon dioxide in the atmosphere.
The idea was first proposed in 2013, but was largely put on hold because, as Kate notes, “it was said that it would only work if clouds had implausible properties”. For example, the models suggested that water should remain in the atmosphere for a long time – much longer than it usually is on Earth – so the whole possibility seemed unlikely.
Using a 3D model of the planet’s atmosphere, Kate and his team set out to work. The missing piece was the amount of ice on the ground. If too much ice covered Mars’ surface, it would create surface moisture that favors lower clouds, which are not thought to make planets too hot (or to cool them, because the clouds reflect sunlight off the planet).
But if there are only patches of ice, as there are at the poles and mountain tops, then the air on Earth becomes drier. These conditions favor higher cloud cover, which tends to heat up the planets more easily.
The model results showed that scientists may have to rule out some crucial assumptions based on our planet in particular.
“In the model, these clouds behave very differently from the Earth,” says Kate. “Building the models on Earth’s intuition will not work, because this is not the same as the Earth’s cycle at all. Water that moves water quickly between the atmosphere and the surface.”
On Earth, where water covers nearly three quarters of the surface, water moves rapidly and unevenly between the ocean, the atmosphere and the Earth, and moves in vortices and vortices that make some places mostly dry (desert) and others (Amazon). In contrast, even while it was most habitable, Mars had less water on its surface. When water vapor reaches the atmosphere, in a kite model, it stays so.
“Our model indicates that once the water entered the atmosphere of early Mars, it remained there for a long time – about a year – creating the conditions for the formation of long-range clouds at high altitudes.” Remember the kite.
The NASA rover should be able to test this idea in multiple ways, such as analyzing gravel to reconstruct past atmospheric pressure on Mars.
Scientists say understanding the full story of how Mars gained and lost heat and atmosphere could help in the search for other habitable worlds.
Kate asserts that “Mars is important because it is the only planet we know that has the ability to support and then lose life.” “The long-term stability of the Earth’s climate is extraordinary. We want to understand all the ways in which the long-term climatic conditions of a planet collapses, and all the ways (not just the Earth) that can sustain it.” This paper identifies a new field of comparative planetary habitability. “