Carbonbergs of the Kessel Run: What could their actual composition be?

As we currently observe and celebrate the end of the basic Star Wars ennealogy (=nine-part series; Internet tells me my preferred choice “nonalogy” is not a word!), watching, maybe multiple times, Star Wars: Episode IX- The Rise of Skywalker, I think back, relative to this blog’s theme, on the couple carbon material references in the series. One is carbonite of Episode V, Star Wars: The Empire Strikes Back, a substance that through the rapid freezing of carbon gas is used for preservation of substances or artificial hibernation of beings, such as the captured Han Solo, later released from his suspended animation by Princess Leia in the beginning of Episode VI, Star Wars: The Return of the Jedi.

The other, more “geologic”, carbon-material mention is the carbonbergs of the 2018 film, Solo: A Star Wars Story . This movie is a “standalone” Star Wars story, which, like Rogue One: A Star Wars Story, serves as a prequel to the original Star Wars film, Episode IV: A New Hope. While Rogue One ends, time-wise, just before (like days before) the start of A New Hope,  Solo, and its depiction of Han Solo’s record-setting Kessel Run through the Akkadese Maelstrom, occurs about 10 years before that.

Carbonbergs, according to Wookiepedia, are “large, drifting masses of solid carbon that could be encountered in realspace. Among other hazards, the Akkadese Maelstrom notably contained planet-sized carbonbergs that routinely crashed into each other, creating gravitational chaos.” In the middle of the Akkadese Maelstrom, was the planet Kessel, the source of “spice”, a group of drugs mined and refined for both legitimate medicinal and illegitimate recreational purposes and a target of smugglers, like Han Solo, and nefarious political entities and operators.

FIGURE 1: Map of Akkadese Maelstrom with various Kessel Run trajectories from https://starwars.fandom.com/wiki/Akkadese_Maelstrom .

The Kessel Run was the route through the cyclonically-shaped maelstrom to planet Kessel and usually was a spiral route through an uncluttered channel (Figure 1). A shorter route could be taken by cutting across the whorls of concentrated ice chunks, carbonbergs, interstellar gas, other debris, monsters, plus a strong gravity well (destructive but not as strong as a black hole). The distance or length of the traditional Kessel Run route is 18 parsecs, but Han’s record-setting run, famously bragged about in A New Hope (watch https://www.youtube.com/watch?v=fjYuw6zWk_Y at 10-20 sec.), was about 12 parsecs. (People have complained over the decades that using “parsecs” was incorrect since parsec is a unit of distance not time. However, the apologia is that Solo was indeed talking about distance since his record-setting route was done over a shorter distance than any previous ship, taking him through a more dangerous part of the maelstrom. The shorter route also resulted in a faster time.)

Carbonbergs, as described above, are solid carbon, which assumably means elemental or native carbon, not a carbon compound that includes other elements like hydrogen, oxygen, nitrogen, silicon. In a movie clip of the Solo Kessel Run, the Millennium Falcon slides on a big carbonberg ripping off part of the landing gear (https://www.youtube.com/watch?v=cnmbVQcENf8; Slide occurs at 1min 26 seconds). Rob Brewdow of Industrial Light and Magic, describes the scene: “in the middle of the Kessel run when we’re coming up to that ice, that giant carbon berg, that Han does the slide on, we actually rip off the front two landing gears”. 

 

FIGURE 2: Passage between two carbonbergs just prior to reaching planet Kessel from Solo: A Star Wars Story. (Snap taken at ~1:45 https://www.youtube.com/watch?v=cnmbVQcENf8 after escaping gravity well.)

However, that description (“ice” and “slide”) implies an icy carbonberg. With ice elsewhere in the maelstrom, and space being freezing cold, and the analogous name to “icebergs”, it suggests perhaps some frozen deposition process or mix of ice and carbon in the carbonbergs. There are a couple instances of icy carbon-bearing materials on both Earth and the solar system. One is methane clathrates, AKA methane hydrates, methane (CH4) is trapped within a cage-like crystal structure of water ice. These are found in the Earth’s deep ocean and possibly moons of Jupiter, Kuiper Belt Objects, and comets. 

A second example is bladed ice “penitentes”, named for their similarity to contrite kneeling figures. With a texture similar to the jagged carbonbergs (Figure 3), penitentes are found in South America, and are postulated to exist on the Jovian moon Europa and on Pluto. On Earth, they form in “cold and dry conditions at tropical latitudes, for example, in the Andes Mountains of northern Chile. They begin to form when a field of ice naturally develops small pits in its surface. When the Sun is nearly overhead, sunlight preferentially strikes the bottom of these pits, warming the ice. This warming ice doesn’t melt in a traditional sense: The air is so dry that the heated ice immediately vaporizes into gas in a process called sublimation. As sublimation continues, the pits deepen. Over time, the cumulative sublimation eats away at ice, creating penitentes with typical heights of 1–5 meters.”  Like penitentes of Earth, the ones on Europa, which could be 15 m tall, would be water ice. On Pluto, they are possibly made of frozen methane and stand 500 m tall. 

 

FIGURE 3: Penitentes on slopes of the dormant volcano Llullaillaco, Chile/Argentina border. (Photo from https://eos.org/articles/microbes-spotted-on-blades-of-ice-high-in-the-andes )

But, the description of carbonbergs does say “solid carbon” so despite their slippery surface, they should not, by definition, be a material including other elements or mixed with ice. Pure carbon crystalline allotropes (differing atomic arrangements of same element) include cubic diamond (and its hexagonal polymorph lonsdaleite), fullerenes, and graphite. (That is allotropes known to us Earthlings.) Diamonds have a network crystallographic structure, and, truthfully, if the carbonbergs were made of diamond I think they would have told us that.

Fullerenes are arrangements of carbon atoms in a closed hollow ball/sphere or cylinder shape, and have been found in interstellar space. The round molecular shape of some fullerenes called “buckyballs”, because of resemblance to Buckminster Fuller’s geodesic dome, makes them useful as lubricants or lubricant additives. A one-atom thick flat/unfolded sheet alone is called graphene. Crystalline fullerene (fullerite) does look a bit like a small version of a carbonberg (Figure 4). Fullerite has a hardness comparable to diamond but does not cleave as nicely. 

 

FIGURE 4: Fullerite (no scale given on photo). 

However, my choice for the mineralogy of carbonbergs would be graphite (Figure 5). The loose bond between layered sheets of carbon atoms in graphite makes it useful as a low-friction lubricant. As any mineralogy student learns, graphite has a very slippery surface, and is relatively soft so one can make marks on paper with it (Ancient Greek word “grapho” means “to write”). Therefore, the Millennium Falcon could slide on a graphitic carbonberg without requiring any ice to be present, assuming the carbon sheets will still slip relative to each other in the cold vacuum of space. 

 

FIGURE 5: Terrestrial graphite from Baffin Island, Canada; crystals 10-15 cm high.

Graphite has indeed been found in space. Carbon is formed by fusion in the interior of stars, and there are such things as “carbon stars” in which the element carbon is more abundant than oxygen. The lower-gravity carbon stars can lose a lot of their mass, so the carbon becomes part of the interstellar dust. Graphite grains, commonly round or onion-shaped, are found in presolar dust (AKA stardust) and have been found on Earth entombed in meteorites. Presolar dust is formed in stars that predate our Sun. (Actually, the onion-shaped grains could be disordered carbon.) While stardust graphite, as we know it, is microscopic in size (Figure 6), in the fantasy universe of Star Wars, we can certainly imagine graphitic carbonbergs of fantastic planetary size.

 

FIGURE 6: Scanning electron microscope photos of micron-size graphite in stardust (Jadhav and others, 2013)