Introducing the ultimate sci-fi planet tier list:
- Arrakis (Dune) – an investigation into the substitution of plants with giant worms
- Earth (The Wandering Earth) – can we turn Earth into a spaceship?
- Earth (Snowpiercer) – can we mimic volcanoes to stop climate change?
- Pandora (Avatar) – on the floating islands of Avatar
- Vulcan (Star Trek) – can nuclear warfare permanently impact our magnetic field?
- Dr. Miller’s Planet (Interstellar) – the physics of orbiting a black hole
- Felucia (Star Wars) – can giant mushroom forests come to be?
I strongly believe that science-fiction is a personality trait. When one sci-fi nerd meets another, there is an unspoken acknowledgement that each nerd has traversed unknown, breathtaking planes, and has ascended the orthodox state of being. Now, with such breadth of imagination, one can only speculate the imbalance in the fabric of the universe caused by an ineffable union of science-fiction nerds and actual science.
(It is in the rare instance that these minor shockwaves materialise– for instance, as seen in Elon Musk.)
For anyone who has perhaps descried a familiar sci-fi title in the list above, or anyone who holds any magnitude of interest in science and fiction, this tier list is gifted to you in the hopes that you might share our love for this special convergence between reality and storytelling.
Kicking off this planetary tier list, we have Arrakis, a planet undoubtedly worthy of the epithet Dune.
Because it is indeed covered with many, many sand dunes.
Frank Herbert’s ecological magnum opus of a planet is the epitome of Chekhov’s gun: a massive desert planet whose conditions are antithetical to life and begets thriving desert folk- the Fremen-and gargantuan sandworms averaging (that’s right: AVERAGING) 200 metres. How many questions us readers must have! For the sake of concision, I’ll look to answer some of the ecological questions about Arrakis.
Let us first address the elephant in the room. Where in the world does the 23.58% oxygen constituent of the Arrakian atmosphere come from? All known “intelligent” life forms require oxygen, and the atmospheres of all habitable planets contain at least 19% of it. One glance at Dune (1984) suggests a decided absence of photosynthesising plants. On an orthodox Earth-like system, photosynthetic autotrophs evolve from simpler organisms and begin evolving oxygen as a by-product of their food- a process dramatically entitled “The Great Oxidation Event”.
On Arrakis, however, the apex predator, the Sandworm, maintains the dual role of also being a primary producer, and is responsible for producing all oxygen required to sustain life. We have never found an organism such as this- capable of photosynthesising, let alone becoming, a net producer of oxygen. So here is a speculative explanation as to how this could occur:
The worm may have developed a mechanism similar to that of photosynthesis, but uses a different source of oxygen to power these reactions.
In photosynthesis, organisms break down water (H2O) to produce oxygen (O2) and hydrogen ions (H+, essentially electrons), the latter of which provides energy for the production of sugars. However, there is little water on Arrakis. So how can we remedy this? Knowing that part of the worm’s diet involves sand, a user on Reddit provided a solution, suggesting the electron donor could be silicon dioxide (SiO2 or sand), which can be oxidised to produce O2 and Si2+ or Si4+. The worm then uses the Si2+ charge gradient to generate energy.
Yet this requires four times more energy than needed to hydrolyse water, so energy from sunlight alone may be insufficient. Thus, perhaps the worm burrows extraordinarily deep into the sand and utilises geothermal energy to power this reaction. This speculation opens an avenue to alternative Arrakian biochemistry, which suggests that life on Arrakis could be silicon based. This element has been plausibly considered the basis of an alternative biochemical system, as silicon has many similarities to carbon, such as tetravalency and alike chemical properties due to their shared occupancy of Group 14 on the periodic table.
It was suggested by The Dune Encyclopedia that the inside of the worm contains gaseous products as a result of its metabolism, including methane, ethane, propane and butane. The heat from the friction of the worm’s movement through the sand is thought to have ignited these products, keeping an eternal flame perennially alight within the worm’s belly (not to mention the heat discharged by metabolic processes of a 200 metre worm would far outpace our constant internal body temperature of around 37 degrees). Though this heat is insufficient to power silicon-dioxide oxidisation, it would certainly make an ideal environment for sulfide-oxidising bacteria, found in trophosomes (bacterial cavities for symbiotic relationships to occur) of tube worms in deep-sea vents. These bacteria are chemoautotrophs, meaning they fix organic compounds and produce oxygen by oxidising chemicals rather than water.
However, an organism as large as the worm is unlikely to have been able to evolve given the sand medium, as it is predicted to weigh around 200, 000 kg, requiring calcium bones of 0.5 metre radius (weighing three quarters its body weight). Herbert solves this problem by attributing water-like properties to Arrakian sand, which would help support its mass and make its growth capacity almost indefinite. In water, the larger the organism, the faster it travels; its motion through water is opposed only by friction (a function of surface area) and not by gravity, as us terrestrial plebs are. Of course, Fremen wouldn’t be able to walk on the sand, but once again, science fiction asks us to suspend disbelief.
I want to discuss one more thing, which is whether there is potential for an Arrakis-like exoplanet to exist in our universe. We have two main contenders:
Mars. In Dune, ecologist Pardot Kynes finds “a glaring white surprise in the open desert… salt. Now he was certain. There’d been open water on Arrakis–once”. The presence of minerals like jarosite on Mars has been confirmed by NASA Mars Exploration Rovers, and can only be formed in wet conditions, indicating a parallel with Arrakis of a more agreeable climate in the past.
Mars, like Arrakis, also lacks “a dominant, planetary-scale magnetic field” (R. Lorenz, The Dunes of Dune). This is contrary to Earth’s “strong magnetic dipole”, which is proposed by the Dynamo Theory to be generated by its rotating iron core. On Arrakis, Fremen use a paracompass to navigate “previously mapped magnetic anomalies”, which would also theoretically function on Mars.
Alternatively, dunes have been found in abundance on Saturn’s moon, Titan, which also contains lakes and seas of liquid hydrocarbons. Perhaps, in our hunt for the sandworm, we will find it traversing the methane waters of Titan with silicon in its backbone.
With all that said, what rank should Arrakis get? With its magnificent ecological wonder, phenomenal scientific insight and real-world parallels, I see fit to give Arrakis a D.
D For Dry.
Bibliography:
https://en.wikipedia.org/wiki/Dynamo_theory
https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Silicon_biochemistry
“The Biology of the Sandworm” 2008 by Sibylle Hechtel, Ph.D.
“The Dunes of Dune” 2008 by Ralph D. Lorenz, Ph.D.
“The Shade of Uliet” 2008 by David M. Lawrence
2019). Reddit. What is the plausible bio-energetic of the sand beast ecology? https://www.reddit.com/r/dune/comments/8um61h/what_is_the_plausible_bioenergetic_of_the_sand/e1h1x7z/?utm_content=permalink&utm_medium=api&utm_source=reddit&utm_name=dune
McNelly., W.E. (1984). The Dune Encyclopedia. The Berkley Publishing Group.
