Dune: what the climate of Arrakis can tell us about the hunt for habitable exoplanets

The conversationFrank Herbert’s Dune is an epic science fiction story with an ecological message at its core. The novels and films are set on the desert planet Arrakis, which several characters dream of transforming into a greener world – just as some imagine Mars today.

We examined Arrakis using a climate model, a computer program similar to those used to make weather forecasts. We discovered that the world Herbert had created, long before climate models even existed, was remarkably accurate – and would be habitable, if not hospitable.

However, Arrakis was not always a desert. According to Dune lore, 91 percent of the planet was once covered by oceans, until an ancient catastrophe led to desertification. The remaining water was further removed by sand trout, an invasive species brought to Arrakis. These spread and carried liquid into cavities deep underground, making the planet increasingly drier.

To see what a big ocean would mean for the planet’s climate and habitability, we now used the same climate model: we threw in an ocean without changing any other factors.

If most of Arrakis were flooded, we calculate that the average global temperature would drop by 4°C (7.2°F). This is mainly because oceans add moisture to the atmosphere, leading to more snow and certain types of clouds, both of which reflect the sun’s energy back into space. But it is also because the oceans on Earth and (we assume) on Arrakis emit ‘halogens’ that cool the planet by depleting the ozone layer, a powerful greenhouse gas of which Arrakis would have significantly more than Earth.

Model of Arrakis

The authors gathered information from the books and the Dune Encyclopedia to build their original model. They then added an ocean with an average depth of 1,000 meters (3,280 feet).

Image credits: Farnsworth et al, CC BY-SA

It is not surprising that the ocean world is a whopping 86 times wetter, because so much water evaporates from the oceans. This means that plants can grow because water is no longer a finite resource, as in the desert of Arrakis.

A wetter world would be more stable

Oceans also reduce extreme temperatures, because water heats and cools more slowly than land. (This is one reason why Britain, surrounded by oceans, has relatively mild winters and summers, while places far inland tend to be hotter in summer and very cold in winter). The climate of an ocean planet is therefore more stable than a desert world.

In the Arrakis desert temperatures would reach 70°C (158°F) or more, while in the ocean state we estimate the highest recorded temperatures to be around 45°C (113°F). That means that the ocean Arrakis would be livable even in summer. Forests and arable crops could grow outside the (still cold and snowy) poles.

However, there is one disadvantage. Tropical areas would be ravaged by large cyclones because the vast, warm oceans would contain much of the energy and moisture needed to create hurricanes.

The search for habitable planets

None of this is an entirely abstract exercise, as scientists looking for habitable “exoplanets” in distant galaxies are also looking for this sort of thing. Currently, we can only detect such planets using huge telescopes in space to look for planets similar to Earth in size, temperature, available energy, ability to host water, and other factors.

Graph of habitability, Y-axis is Earth Similarity Index, X-axis is Planetary Habitability Index

Both desert and ocean Arrakis are significantly more habitable than any other planet we have discovered.

Image credits: Farnsworth et al, CC BY-SA

We know that desert worlds are probably more common than Earth-like planets in the universe. Planets with potentially life-sustaining oceans tend to be in the so-called ‘Goldilocks zone’: far enough from the sun to keep it from getting too hot (so further away than boiling-hot Venus), but close enough to keep everything from being frozen (so closer than Jupiter’s icy moon Ganymede).

Research has shown that this habitable zone is particularly small for planets with large oceans. Their water is at risk of either freezing completely, making the planet even colder, or evaporating as part of a runaway greenhouse effect in which a layer of water vapor prevents heat from escaping and the planet becomes hotter and hotter.

The habitable zone is therefore much larger for desert planets, because on the outer edge they will have less snow and ice cover and absorb more of the sun’s heat, while on the inner edge there is less water vapor and therefore less risk of a runaway. greenhouse effect.

It is also important to note that although the distance from their local star can provide an overall average temperature for a planet, such an average can be misleading. For example, both the desert and the ocean in Arrakis have a habitable average temperature, but the daily temperature extremes on the ocean planet are much more hospitable.

Currently, even the most powerful telescopes cannot observe temperature at this level of detail. They also cannot see in detail how the continents are arranged on distant planets. This could again mean that the averages are misleading. For example, while the ocean Arrakis we modeled would be very habitable, most of the land is in the polar regions, where there is snow all year round – so the actual amount of habitable land is much less.

Such considerations may be important in our own distant future, when Earth is expected to form a supercontinent centered on the equator. That continent would make the planet far too hot for mammals and other life to survive, potentially leading to mass extinction.

If the most likely habitable planets in the universe are deserts, they could be very extreme environments that require significant technological solutions and resources to support life – for example, desert worlds are unlikely to have an oxygen-rich atmosphere.

But that doesn’t stop people from trying. For example, Elon Musk and SpaceX have big ambitions to create a colony on our nearest desert world, Mars. But the many challenges they will face only emphasize how important our own Earth is as a cradle of civilization – especially since ocean-rich worlds may not be as plentiful as we would hope. If humans eventually colonize other worlds, they will likely face many of the same problems as the characters in Dune.

The conversation

Alex Farnsworth, Senior Research Fellow in Meteorology, University of Bristol; Michael Farnsworth, Research Leader, Future Electrical Machines Manufacturing Hub, University of Sheffield, and Sebastian Steinig, Research Associate in Palaeoclimate Modelling, University of Bristol

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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