What's up with Star Wars' bizarre 'mono-climate' planets?
On this May the Fourth, explore the unusual worlds of a galaxy far, far away.
Everywhere we look, a long time ago, in a galaxy far, far away, there are weird worlds that seemingly possess only one climate. How does that happen, though? How could these 'mono-climate' planets come to be?
Here on Earth, we have numerous climates, from tropical rainforests and scorching deserts near the equator, to the icy wastelands of the north and south poles. These are spread about on four major land masses — the Americas, Afro-Eurasia, Antarctica, and Australia — that cover about 30 per cent of the planet's surface, with oceans making up the rest. Latitude and general weather patterns are the dominant factors that control exactly where these climates exist.
In this image of Earth, snapped by the DSCOVER satellite's EPIC camera on July 15, 2020, we see snow and ice, mountains, plains, grasslands, forests, jungles, oceans, and deserts. (NASA)
In the Star Wars galaxy, though, most (if not all) of the habitable planets and moons we've seen have only one climate that covers the entire world.
Although the action often takes place on just a small portion of the surface, seen from orbit, even planets that are reasonably Earth-like still lack some basic features that should exist there, such as polar ice caps. So, how could worlds have developed like this, naturally?
Desert Planets
Tatooine is a desert world baked by twin stars — Tatoo I and Tatoo II.
Like Mars, it likely had a much wetter environment in its past. The Dune Sea is evidence of it having a vast ocean, which probably dried up due to the system's binary stars heated up as they aged.
Or, perhaps, like Jakku, with its immense impact scar, some cataclysmic event may have caused the planet to lose its water. In either case, there is likely not enough moisture on the planet for polar ice caps to form.
Other desert worlds in Star Wars include Mandalore, Geonosis, Jedha, Pasaana, and Arvala-7.
Swamp Planets
Dagobah, the planet where Jedi Master Yoda went into seclusion after the Clone Wars, and where he trained Luke Skywalker, is completely covered in swamps and bogs. This is very likely due to the thick layer of clouds that blankets the planet, similar to what we see on Venus (although not to the same extreme).
The planet's persistent clouds would trap light and heat, producing a fairly uniform range of temperatures across the entire surface.
'Mud' planets, such as Mimban and Wobani, are probably quite similar, although they apparently lack the abundant biosphere of Dagobah.
Forest Worlds
Kashyyyk, the homeworld of the Wookiees, is an entire planet covered by expansive rainforests and jungles, with numerous small tropical seas. The planet's lack of an axial tilt means it does not experience seasons.
Also, the truly massive biosphere of this planet, with wroshyr trees growing up to 400 metres tall, may be what maintains relatively uniform temperatures from pole to pole.
Other forest worlds we've seen include Tokodana, the planet that became Starkiller base, Dantooine, Sorgan, and Corvus. How these worlds maintain their uniform climate is not as clear.
Snowball Planets
An ice planet like Hoth could develop fairly easily, simply by having an Earth-like world form farther out from its star. It's also possible that Hoth had simply gone through a climatic change, similar to the 'Snowball Earth' stage our planet may have gone through around 650 million years ago.
It's thought that, at the time, the eruption of a supervolcano may have pumped enough dust or sunlight-reflecting sulfur compounds into the atmosphere to cool the climate. It is also possible that a surge in ocean life may have reduced the concentration of carbon dioxide in the atmosphere, triggering a global cooling event.
Habitable Moons
For the moons of Yavin IV and Endor, the infrared radiation (heat) given off by the gas giant planets they orbit can supply more than twice the energy the moons would receive from their system's parent star.
This would be an abundant heat source, especially if the planet was reasonably close to its star (perhaps at the same relative distance that Mars is from our Sun). This added heat would help polar regions of the moons maintain a more temperate climate, as well.
Lava Planets
Once a lush world, Mustafar is a volcanic planet that was plunged into a gravitational 'tug-of-war' between two immense gas giants after it was knocked out of its original orbit. The intense gravity of these two massive worlds would squeeze and squish Mustafar's core, ramping up the heat inside the planet until it caused volcanoes to erupt across its surface.
This same kind of 'tidal squeezing' is evident in our own solar system, with Jupiter's closest Galilean moon, Io, being one of the most volcanically active objects in the system.
The sunlit hemisphere of Io is shown here, marked by numerous volcanoes 'powered' by the tidal squeezing of the moon by massive Jupiter, as well as Europa and Ganymede. (NASA/JPL-Caltech/SwRI/MSSS/Thomas Thomopoulos)
Moons like Jupiter's Europa and Saturn's Enceladus likely have oceans of liquid water, even at their far distance from the Sun, due to the added internal heat from this same kind of tidal action.
Ocean Worlds
Kamino and Mon Cala are two examples of 'ocean worlds' in the Star Wars galaxy. Both of these planets likely have no dry land at all. From the exoplanets astronomers have discovered in our own galaxy, these two could fall into the "super-Earth" category. With heavier gravity than we experience here, this kind of planet holds on to more atmosphere, and would tend to develop deeper oceans. It's also possible that they simply developed in planetary systems that had more available water, or were under heavier bombardment by comets early on.
As for the climate of these worlds, the global ocean of such a planet would absorb a large amount of incoming solar radiation, and would be slower to give this heat up. With internal ocean currents and likely frequent hurricane-class storms delivering that heat from the equator to the poles, these planets could also maintain fairly uniform global temperatures. Ahch-to, where Jedi Master Luke Skywalker lived during his self-imposed exile, is another example, although this planet had numerous rocky islands. Scarif, which housed the Empire's data vaults, is another example, although its oceans appeared to be shallow, and Crait is likely another, although its oceans have long dried up, leaving behind a planet-wide crust of salt.
This may look like a planet in a galaxy far, far away, but it is actually an artist's representation of TOI 700d, an Earth-sized exoplanet found by NASA's TESS telescope in 2020. (NASA's Goddard Space Flight Center)
There are a few bodies in our own solar system that, if they were closer to the Sun, would be water-worlds. Europa, Ganymede and Callisto, Enceladus and Titan, and even the 'asteroid' Ceres, would qualify.
Terraformed Planets
As we see above, there are many mono-climate worlds in the Star Wars galaxy that could exist simply by natural means. However, several defy explanation if you only look at what could have developed without intervention.
Alderaan, Naboo, and Lothal appear to be some of the most 'temperate' planets in the Star Wars galaxy. Each has (or had) its own dominant terrain, though — Alderaan: mountains, Naboo: hills and lakes, and Lothal: grasslands.
Planets like these would need help to maintain one global climate, though.
Given the technological level of the galaxy, with antigravity, interstellar travel, synthetic intelligence, and so on, it is very likely that the Republic developed the means to terraform (Coruscant-form?) planets. Any world that was suitable, but for some reason did not develop a habitable climate on its own, would then have its climate deliberately adjusted to meet the needs of a new colony.
Artificial weather modification could redistribute heat and moisture across a planet's surface, making as much of it habitable as possible. This could easily include the melting of a planet's polar ice caps, to transport that water to more temperate zones, thus smoothing out any variation of climates that would have occurred without that intervention.
Finally, planets like Coruscant and Hosnian Prime are best described as 'urban planets', or ecumenopoli, due to the fact that nearly every square centimetre of their surfaces is covered in city sprawl.
On Coruscant, the urban environment is so extreme that, to see any of its original surface, residents and tourists need to visit Monument Plaza, on the planet's 5,216th level. There, they can see the summit of Umate, Coruscant's tallest mountain, poking up above the new artificial surface. If Umate was the same height as Mount Everest on Earth, that level would be at over 8,000 metres above Coruscant's original sea level, making the air so thin that you couldn't breathe for long without collapsing.
That implies that Coruscant is completely climate-controlled, with all weather suppressed or altered through technology. Also, with its biosphere reduced to nothing and a population numbering in the trillions, the planet would even need atmospheric processors running constantly to add and refresh the oxygen content of the air.
In reality, many planets in our galaxy (and even other galaxies) will probably have a variety of climates, like Earth. However, given the variety we have discovered so far, who knows what we will end up finding in the future! In the meantime, we can continue to enjoy the multitude of bizarre worlds shown to us in the Star Wars universe.
May the Fourth be with you!