Ancient icy clouds may hold the answer to water on Mars

Researchers from the University of Chicago believe that icy clouds have solved the interstellar mystery of water on Mars.

The discovery infers that a thin layer of icy, high-altitude clouds was responsible for a greenhouse effect that created temperatures capable of accommodating water on Mars, with the desert planet once home to ancient lakes and river systems.

The conundrum of water on Mars has long evaded scientists, with the remnants of its prehistoric river deltas indicating its exitance, but the source of its precipitation remaining unsolved. Perhaps the most perplexing thing is that while rivers flowed and meandered on the Martian planet, there was estimated to be only a third of the sunshine that is exhibited today on Earth. This new study proposes to solve this, employing a computer model to decipher the history of the now baron land– suggesting that icy clouds are the reason behind water on Mars.

Edwin Kite, leader of the study and an assistant professor of geophysical sciences and an expert on climates of other worlds, said: “There’s been an embarrassing disconnect between our evidence and our ability to explain it in terms of physics and chemistry. This hypothesis goes a long way toward closing that gap.”

Previous theories hypothesised that the collision of a gigantic asteroid was to blame – releasing sufficient kinetic energy to warm the planet for water accommodating conditions; however, this was disproved as the effect would last a mere few years, with the deltas existing for at least 100 years.

Instead, Kite and his team reconsidered a theory that was first proposed in 2013 – that high-altitude clouds, like cirrus on Earth, were to blame. This is because even an insignificant amount of clouds in the atmosphere can generate a greenhouse effect capable of substantially raising the planet’s temperature.

To test this theory, the team created a 3D model of the planet’s atmosphere in its entirety, finally capturing the answer they had been searching for – ice on the ground. If ice was covering large portions of Mars, humidity that favours low-altitude clouds would be created, which are not believed to warm planets very much as they reflect sunlight from the planet. However, if the ice were situated at the poles of the planet and the top of mountains, the air would become much drier, creating conditions favouring a high layer of clouds that warm planets.

“In the model, these clouds behave in a very un-Earth-like way. Building models on Earth-based intuition won’t work because this is not at all similar to Earth’s water cycle, which moves water quickly between the atmosphere and the surface,” said Kite.

Three-quarters of the Earth is covered by water, which rapidly oscillates between the land, oceans, and atmosphere. Contrastingly, even at its peak, water on Mars was much sparser, with the water in its atmosphere lingering.

“Our model suggests that once 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-lived high-altitude clouds,” said Kite.

The researchers believe that their findings can help form a more comprehensive understanding of other planets’ propensity to have water.

Kite said: “Mars is important because it’s the only planet we know of that could support life and then lost it. Earth’s long-term climate stability is remarkable. We want to understand how a planet’s long-term climate stability can break down and all of the ways (not just Earth’s way) that it can be maintained. This quest defines the new field of comparative planetary habitability.”

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