Friday, 27 November 2020

Antique Paleoart: Journey to the Center of the Earth

Because I am nothing but unoriginal I decided to basically rip off Love in the Time of Chasmosaur’s long-running Vintage Dinosaur Art series, though of course with a twist. These definitions are naturally somewhat subjective, but a cultural object is usually defined as “vintage” if it is at least 25 years old (meaning Jurassic Park is already vintage and its first sequel will be as well in two years). Once something is older than 100 years it however stops being vintage and instead becomes an antique, which is where I want to jump in. In this new category I want to take a light-hearted look at paleoart (mostly from books), which is at least 100 years old, which at the point of writing would be anything made before 1920. To kick this off nicely I decided to begin with a true classic: Voyage au centre de la Terre by none other than Ur-sci-fi-author Jules Verne. While it was technically first published in 1864, the definitive and most famous editon was the 1867 reissue, which featured artwork by one Édouard Riou. Riou may perhaps not be such a big name anymore in today’s discussion around paleoart, considering all the Knights, Burians and Pauls that came after him, but he is still indispensable for the history of the medium for illustrating Louis Figuier’s The Earth before the Deluge in 1863 (which I still need to get my hands on). While Figuier’s book still worked off a biblical narrative, it was the first major book aimed at general audiences that told and illustrated Earth’s geologic history through the ages, making it the precursor to basically every popular non-fiction dinosaur/prehistory-book written after it. Without it we might never have had books like Life through the Ages, All about Dinosaurs, Life before Man or All Yesterdays and paleoart might still be relegated to dry scientific papers. It was also exactly this work which most scholars agree was the inspiration behind Verne’s novel.

In the rare case you do not already know the basics of the story, the novel follows the adventure of the clumsy German geology professor Otto Lidenbrock and his nephew Axel, who, together with the stoic Icelandic guide Hans, follow the trails of a long-dead monk down the lava tubes of a long-dead volcano to discover a fantastical biosphere deep under the Earth. The first third of the novel mainly concerns the rather drab travel towards and down the volcano, without any wildlife-encounter, but I still wanted to include this Riou-illustration of a gigantic crystal cavern. The reason is that, while in Verne’s time this was seen as fantastical, real-life caverns like this have been discovered in the form of the Naica Mine in Mexico. Another thing to add to the long list of things Verne predicted, which also includes travelling to the Moon, giant submarines, skyscrapers and even the internet. Take that H. G. Wells!

Technically our first illustration of extinct life comes when the expedition team travels through a naturally hollowed out coal-deposit. While not outright stated in the text, it is quite clear that what is depicted here are petrified Calamites trees. In the Carboniferous these giant horsetails, together with scale-trees, were near ubiquitous in the ancient coal swamps. Fossils like these have even been found near where I live at the Swiss Tödi mountain and the town of Dorénaz. Axel, the narrator and whose opinions basically reflect mainstream geology of the time (as opposed to his uncle who’d be considered an odd crank nowadays), uses this passage to tell us a bit about the Carboniferous and Devonian times and their inhabitants. Interestingly for us today, he muses that through the overconsumption by the industrialized nations the world’s coal-deposits might be completely depleted in about three centuries. From Jules Verne’s POV while writing the novel, that would be in around the 2160s. Since the global industrialization has only expanded since his time I wondered how well this prediction would hold up. At least according to this paper our known coal deposits might last until the 2110s, with all other fossil fuels already running out by the 2040s. I have however also found some sources claiming that coal might already run out by the 2060s, so Verne’s prediction might be 50 – 100 years too optimistic. Of course, none of this would be a problem if we simply stopped using fossil fuels and start relying on renewable resources.

After travelling further down the lava tubes, the expedition finally comes to a titanic, perhaps continent-sized cavern, which houses the Lidenbrock Sea and which is lighted by electric clouds under the cave ceiling. After walking along the sea’s beach they come across a forest of giant mushrooms, a truly iconic image. While this was of course pretty fantastical even in Verne’s time, in hindsight there is something funny about this, seeing how we nowadays know of Prototaxites, a Devonian, pillar-shaped lichen which grew about 8 meters tall and dominated the landscape before actual trees evolved. Prototaxites had been known since 1843, though the suggestion that it was a fungal organism had not been made until 2001. Maybe we can add this to the list of Verne’s predictions too. Inside the mushroom forest they also find Carboniferous trees, living versions of the ones they previously saw in the coal ore. Among these on the ground they find bones of various extinct mega-mammals, like Mastodon, Megatherium and Deinotherium. It is left open whether these are the remains of animals which recently lived in the underground forest or if these are fossils swept here from the above-world by sinkholes or similar geologic forces. As they do not see any living ones, Axel assumes the latter, while Lidenbrock likes to think it is the former.

Shortly after, they build a raft and decide to cross the Lidenbrock sea to explore the other shore. At sea they encounter gigantic algae and catch blind descendants of the Devonian placoderm Pterichthys (today referred to as Pterichthyodes, the animal which I currently use as my profile picture). This first encounter with a genuine prehistoric animal makes Axel daydream about travelling to the past and encountering other extinct lifeforms. This dream is what is depicted in the above image by Riou. The mammal on the bottom left is, I assume, Anoplotherium, the one on the right is not an anteater but the giant sloth Megatherium. Yes, back then it was thought that Megatherium had a trunk like a tapir, as can also be seen with the famous statues at the Crystal Palace Park. In more recent years it has also come into question if giant sloths like these, especially the ones living in areas like Florida or Brazil, really were as shaggy as often depicted instead of being naked like most large mammals. Speaking of fur, the two mastodons at the beach are notably drawn without any. As recently discussed by Mark Witton this may actually be closer to the truth, as the idea of mastodons being as hairy as mammoths is entirely born out of paleoartistic convention rather than actual evidence. Nice job, Riou. The Mesozoic reptiles in the background are of course very much of their time, but still give the piece a nice atmosphere. The marine saurians greatly resemble the same ones from Riou’s previous work on La Terre avant le Deluge and the pterosaurs also remind me of another piece of art, but I cannot quite put my finger on which one. Oh, and look, a moa! That should fill our dinosaur-quota for the day. On its own this is a really nice piece, even if deliberately anachronistic, but what diminishes it is that it is just a dream-sequence. But do not worry, this initial disappointment is just build-up for when the real-deal comes!

After a few days at sea, the expedition tries to fathom the depth of the water by letting down a pickaxe attached to a rope. After they pull it out of the water again they see that the axe has been heavily dented by gigantic, crocodile-like bite-marks, a definite sign that they pissed off something big and scary. The next day they are woken up as a gigantic animal hits their raft. What I really like about this image is the sort of creepy vibe. This could just as well have been an illustration in one of those Bernard Heuvelmanns’ books about sea-serpents or other marine cryptids… which is of course because the modern vision of sea-monsters was based off this era’s science on Mesozoic marine reptiles. In hindsight, books like Journey to the Center of the Earth or Arthur Conan Doyle’s The Lost World probably contributed a lot to the “prehistoric survivor paradigm” which has made cryptozoology the laughingstock that it is nowadays.

After the initial shock they see a multitude of animals in the distance, a whale, a crocodile and a lizard on one side and a giant tortoise and a sea serpent on the other. As they come closer however they see that it is just two creatures whose body-parts they mistook as belonging to separate animals: an ichthyosaur and a plesiosaur. To us this mistake may sound odd, but it emphasizes just how alien these animals were to the people of the mid-nineteenth century. I bet that this was Mary Anning’s first reaction upon discovering Plesiosaurus. What follows this odd encounter is what most people would consider the signature scene of the novel. In fact a colored version of this image is used as my edition’s cover. Now of course we could spend all day talking about how outdated this reconstruction has become, but come on man, scenes like this are what we are all here for. Raw antediluvian brute force! It is interesting to compare this to Riou’s previous illustration of the two animals in Deluge. There they do not fight, but just look mildly annoyed at each other. In Deluge they also are more anatomically accurate and have smooth skin, while here they look more monstrous and are decked out with almost turtle-like armor-scutes. It is probably safe to say that Riou deliberately made the animals more exaggerated here for added entertainment value. Also interesting to note is how this image demonstrates the fact that people at this time thought the sclerotic ring of ichthyosaurs was visible in life, as can also be seen at the Crystal Palace sculptures.

After an odd encounter with a geyser and a kugelblitz, the expedition finally lands on the far side of the shore. There they encounter a giant fossil graveyard, strewn with the bones of various extinct mammals and reptiles. It is again left uncertain if these bones came from animals living underground or sank down here from above.

Among the bones they shockingly find the remains of a prehistoric human. Mind you that this was at a time when the existence of humans in faraway geologic history was still controversial and remains of fossil hominins were still rare. Charles Lyell had just written Geological Evidences of the Antiquity of Man in 1863 and the identity of the neanderthal remains was still called into question by some. What follows is Otto Lidenbrock audibly daydreaming of standing in his lecture hall and making fun of the scholars which doubted the antiquity of man. Though something seems off with this haunting image The skeleton does not look like a fossil, but rather like a mummy as it still has hair and skin.

After crossing the graveyard, Otto and Axel enter a large forest filled with Cenozoic plants. There they find a herd of still living (and naked) mastodons and, dumbfoundingly, a gigantic human leaning against a tree with a large club, apparently tending the mastodon herd like they are its cattle. The sight is so terrifying that the two explorers flee the forest, in fear that the giant might spot and attack them. Axel finds this encounter so unbelievable that he tries to tell himself in retrospect that what they saw just was just a large ape, but we readers know better thanks to Riou’s illustration. The way he drew the jungle has a certain eldritch quality to it. Together with the frightening sight it reminds me a bit of scenes from H. P. Lovecraft stories. One wonders if there was an influence, though Lovecraft would not be born until 1890 and as far as I am aware did not read much from Jules Verne. That said, both Verne and Lovecraft had Edgar Allan Poe as an influence. Getting back to the shore of the Lidenbrock sea, Otto and Axel find more signs of Arne Saknussemm, the Icelandic monk that led them to this journey. With their raft they follow his path, landing in another lava tube which ejects them out of the Italian volcano Stromboli, concluding their journey.

A few words on the hollow earth and dinosaurs

Despite the title, the protagonists of the Verne novel never reach the center of the Earth. According to Otto, the Lidenbrock Sea is “only” 35 miles (56.3 km) under the Earth. That is close to the boundary between the crust and the upper mantle, so admittedly still impressive, but very far from the center. In fact, at the end Axel is strongly of the opinion that his uncle still is a nutjob for thinking the Earth is hollow and that everything they encountered was nothing but local exceptions. Hence it is very ironic that this became one of the signature stories to influence hollow earth fiction. The idea of a hollow earth or at least large, underground lost worlds, did not begin with Verne. Arguably the oldest example of such a story was Dante Alighieri’s Divine Comedia from 1320, wherein at the center of Earth is hell with Satan himself. In a scientific context the idea was first suggested by Edmond Halley in 1692, when he postulated that the interior Earth is made up of multiple independently rotating shells with their own magnetosphere. He came to this conclusion as he tried to explain compass anomalies and the phenomenon of aurora borealis (which we now all know is actually caused by steamed hams). This was further adapted by Scottish mathematician Sir John Leslie, who proposed that there were two small suns in the interior of the Earth providing light to the surface of a concave hollow Earth. Leslie's idea is actually referenced by Axel when he first sees the Lidenbrock Sea. In 1818 John Cleves Symmes also hypothesized about a hollow Earth and proposed that entrances to it could be found at both the North and South poles. This actually inspired multiple arctic/antarctic expeditions trying to find these entrances. One of his most notable believers and approver of such an expedition was John Quincy Adams, the sixth president of the United States of America. Symmes’ theories also influenced The Narrative of Arthur Gordon Pym of Nantucket, an Edgar Allan Poe story from 1838. Despite all this popularity, the idea of a hollow Earth was already disproven in 1774, when Charles Hutton calculated the mean density of our planet, showing that its interior was filled and solid.

Verne’s true contribution to the genre was the connection between subterranean lost worlds and prehistoric life. In all previous stories the Hollow Earth was populated by either fantastic beasts or Atlantis-like civilizations. In my eyes it is clear that Verne himself did not believe in the Hollow Earth, but rather the mainstream geology of his time, and instead simply used this genre as a vehicle to tell a fun and also educational story about geology and paleontology, especially in a time when time-travel fiction did not really exist yet (Wells still had to catch up). I find the association between prehistoric life and underground worlds fascinating in a psychological and cultural context, as in many ways it resembles the reasoning behind ancient beliefs about the afterlife. Why did many old religions believe the world of the dead was underground (think of the Greek Hades or the Jewish Sheol) and not, say, on the Moon? A relative of mine who studied theology put it quite simply: That is where these cultures buried their dead, so it is where the souls of the dead would also stay and dwell. Now, why would prehistoric animals be living deep underground? Because that is where their fossils rest. To explain why these animals are only ever found as frozen carcasses, Siberian mythology actually does say that mammoths are animals which live continually underground like giant moles and once they accidentally breach the surface they instantly freeze to death. Similar stories exist in Native American folklore about fossils. Now compare this with Greek stories like that of Orpheus and Eurydice. The idea of meeting entities from the past while travelling underground was also used in Dante's comedy and various mythologies before him. In some ways the type of Hollow Earth which Jules Verne created then seems like a (subconscious) continuation of such ancient beliefs about the underworld. Images and scenes like the fossil graveyard and the coal mine only add to this baroque sense of remembering the dead (which in the end paleontology is all about when you think about it). However, any such deeper meaning seems to have been lost in later stories inspired by Verne’s novel. Edgar Rice Burroughs’ Pellucidar series, starting in 1914, and Vladimir Obruchev’s novel Plutonia from 2015 both feature a concave Hollow Earth populated by all sorts of prehistoric creatures (and occasionally Tarzan), but use these mostly as fantastical elements rather than being geologically or paleontologically minded. From then on the association with the Earth’s core and extinct life became codified without much sense behind it. The most hilarious example of this is the fact that, according to one of the screenwriters of the 2003 movie The Core (a movie which mind you is well aware that the interior of the Earth is solid and hotter than the sun’s surface), the original script of the film still wanted there to be dinosaurs at the Earth’s core! The movie is hilariously dumb as is, but I would have loved to see that trainwreck. Speaking of dinosaurs, it is odd that none appear in Journey to the Center of the Earth (apart perhaps from that one moa Axel dreams about). As a kid I thought this was simply because dinosaurs were not yet known in Verne's time, but history quickly proved young me wrong. The first known dinosaur, Megalosaurus, was already described in 1827, the Crystal Palace Park saw completion in 1853 and the relatively complete skeleton of Hadrosaurus was discovered in 1858. Édouard Riou himself previously illustrated a fight between Iguanodon and Megalosaurus in Deluge before working for Verne. In the next decade already the infamous Bone Wars between Marsh and Cope would break out. Why did Verne not capitalize on this growing dino-mania and instead resorted to fossil animals which were already long-known at the time? Frankly, I do not know. One also wonders if this “lack” had an influence on the book’s popularity over the years. While it is among his most well-known works, Journey to the Center of the Earth nowadays never seems to be as culturally relevant or popular as his other books, such as Around the World in 80 Days, 20’000 Leagues under the Sea or Around the Moon. Perhaps some dinosaurs would have helped boost its popularity. Though I think there is something deeper behind this. Most of Verne’s stories concern the technologies and possibilities of the present and future, while Journey stands out for being perhaps his only story that is interested in exploring the past. It is also mainly known for being both outdated and impossible. Compare it then, for example, with Around the Moon, which predicted many details of the Apollo moon landings with an almost eerie precision. As discussed previously this difference in popularity/relevance is likely indicative of the modern trend of young people being more interested in technology than fossils. But hey, when worlds collide...

On a final note, I really enjoyed the 2008 movie adaptation when I was younger. Brendan Fraser deserves more love, especially after what he has been through in recent years! This has been it for our first post in this new category. Next time we will take a look at Harry Govier Seeley’s Dragons of the Air from 1901. Thanks for reading and see you until then!

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Related Posts:

Literary Sources:

  • Ley, Willy/De Camp, Lyon Sprague: Lands Beyond, New York 1952.
  • Verne, Jules: Journey to the Center of the Earth, Paris 1864 (German translated edition 1971).
  • Witton, Mark: The Paleoartist's Handbook. Recreating prehistoric animals in art, Marlborough 2018.


Online Sources/Further Reading:

Thursday, 5 November 2020

The Many Mysteries of Darwin IV - Part 1

Fig. 1: The classic cover of the first edition, soon to be replaced by the reprint.

Ever since watching E.T. the Extraterrestrial, aliens were one of the biggest fears I had as a child. This was because most aliens I had seen since then were those weirdly humanoid ones, which are intentionally designed to evoke the uncanny valley. This fear of being abducted by greys or Spielberg’s roasted gremlin subsided when I saw two things: Star Wars, with its light-hearted and imaginative alien life, and a 2005 documentary on Discovery Channel called Alien Planet. Especially the latter made me see the idea of alien life in a new, positive light and gave me hope that we might discover some of it one day. What young me did not realize at the time (because who reads credits anyway?) is that Alien Planet was based off a science-fiction book by painter Wayne Douglas Barlowe. In Expedition a wildlife illustrator goes on a journey to a mysterious and wild planet called Darwin IV and paints the local creatures in all their beauty while detailing his travels. This book was first published in 1990, which means that this year marks its thirtieth anniversary! To commemorate the occasion, Barlowe is now selling a reprint of the book on Echo Point Books. If you never had the chance to read it before, now is your time! Now how do I want to commemorate one of the most monumental works in speculative evolution? By playing armchair-scientist of course!

One of the greatest strengths of Expedition is the great aura of mystery it not only creates but leaves behind about Darwin IV. After the first (and so far only) expedition we leave with more questions than we arrived with. This is what makes it feel almost real, as an actual first encounter with alien life would probably be just as if not more confusing. What I want to do in this post and its sequels is to seriously examine Darwin IV and the life on it in a semi-scientific way and maybe work out a few answers to its many mysteries. While I am doing this in part to put the knowledge I gained in studying Earth System Sciences to good use, my intention is also that we both learn something about real-life star systems, planets, geology and lifeforms in the process. This first post mainly concerns the orbital and geophysical characteristics of Darwin IV.

Fig. 2: The cover of the more well-known Alien Planet documentary, more precisely of the German DVD I owned since childhood.

Before we start, I just want to clarify that I will be very biased and apologetic about some of the criticisms made against the book by people in the spec-evo community. I just love Darwin IV so much that something deep inside me wants something like it to be real. When it comes to questions of plausibility, I will therefore play devil’s advocate (which is fitting since Barlowe has also extensively painted hell).

What does any of this have to do with dinosaurs or paleontology, you ask? You will see in time.

The Darwin System

Darwin IV is part of the Darwin star system. It is a binary star system 6.5 lightyears away, consisting of at least one F-type-main-sequence star and six planets (Barlowe 1990, p. 11-12). If both stars in this system are F-type stars is not exactly made clear, though they are said to be very different in size (p. 12). The real-life binary F-type star systems we know of that contain exoplanets are Upsilon Andromedae, Tau Boötis and HD 142 and in all three the second star is a red dwarf that circles the main F-type star. It is therefore safe to assume that the main Darwin star (let us call it Darwin A) is an F-type that is accompanied by a red dwarf (Darwin B). Now the first obvious question some of you may have is if a planet with large animal life could even exist in such a system. Our own sun is a G-type-main-sequence star. F-type stars can be up to 1.4 times heavier than our own star and are considerably hotter. Binary star systems can also lead to planets with unstable climates, depending on how they rotate which star. That said, Darwin IV’s stated position in the system actually makes its habitability quite plausible. There can be two types of planets in a binary star system: Non-circumbinary (S-Type) planets, which orbit only one star in the binary system, and Circumbinary (P-type) which orbit both stars at once if those stars are close enough to each other. Both types of planets can be habitable given the conditions, but P-types are more likely to be as they have more stable orbits. Darwin A and B are said to orbit so closely to each other that they look like a single star from one of their planet’s surface and Darwin IV orbits both of them at once, making it a P-type planet. Darwin IV being such a circumbinary planet may sound contrived at first, but there are multiple real-life examples of such circumbinary planets. Kepler-47c is one such example and even circles its binary system in its habitable zone. Speaking of which, Darwin IV is said to orbit Darwin A&B at a distance of two AUs or Astronomical Units (p. 12). One astronomical unit is the distance between Earth and our sun, in other words meaning Darwin IV is twice as far away from its sun(s) than we are from ours, which in our solar system would be about the position of the asteroid belt between Mars and Jupiter. Would that not mean the planet should be completely frozen over? No. Remember that F-type stars are larger and hotter than our sun. A 2014 paper determined that the habitable zone of an F0-type star (hottest in the F-class) extends from 2 to 3.7 AUs, while that of an F8-type star (coldest in the F-class) extends from 1.1 to 2.2 AUs (Sato et al. 2014). It is interesting to note that both these ranges are larger than our own sun’s estimated habitable zone which ranges from approximately 0.8 to 1.5 AUs. Darwin IV being 2 AUs away places it firmly well in the habitable zone of all F-type stars. Mind you that Wayne Barlowe accurately predicted this habitable zone 24 years before the study I cited was made. Because we do not know where in the F-class Darwin A is, it becomes difficult to say whether Darwin IV is comfortably in the middle or the rim of the habitable zone. We also are not informed (at least in the book) about the age of the system, which is also significant as the luminosity of a star changes throughout its lifetime. Depending on these two factors, Darwin IV might be (distance-wise) Darwin’s equivalent to Earth, but could also be its Venus, something to keep in mind. The same paper that estimated F-type stars’ habitable zones also determined that lifeforms around these stars are under stronger exposure to damaging UV-radiation, but this can be countered if the planet in question has an ozone-layer (something Darwin IV definitely has) and/or a decent magnetosphere (which it probably has).

Fig. 3: Darwin IV would be a P-type planet.

All that said, even if Darwin IV were not ideally or not at all in its star’s habitable zone, it could still be habitable for its lifeforms as we see. What many people forget or maybe just do not know when talking about habitable zones is that it just describes a region around a star in which without any modification or protection temperatures are in theory capable of maintaining liquid water and are tolerable for life as we know it. In other words, it is a zone determined by simply putting a blank thermometer into empty space and seeing where an astrophysicist would feel comfortable in his spacesuit. It does not take into account things like: Albedo caused by icecaps or clouds, greenhouse effects, densitiy and make-up of atmospheres and nuclear or tidal heating. As a consequence, some scientists consider the classic concept of habitable zones totally useless (Cohen 2002, p. 10) and I must frankly agree. The most poignant demonstration of this is Earth itself, as without its greenhouse atmosphere our temperatures would drop to minus 18 degrees Celsius on average, rendering most or all our surface water into solid ice. Temperature drops close to this have in fact happened billions of years ago, possibly suppressing the development of multicellular life for many millions of years. We are therefore, arguably, outside our solar system’s strictest habitable zone. More examples abound, such as Mars, which had plenty of liquid water on its surface at a time when the sun was at only 70% of its current luminosity, and the moons of the gas giants, far away from the sun but filled with liquid water thanks to the tidal forces enacted by their parent planets. According to calculations such as those by David Stevenson, even rogue planets which do not orbit any star at all but just wander through the eternal darkness of deep space could have liquid water on their surface thanks to a combination of an insulating atmosphere and geothermal heat produced by the decay of radioactive elements (Cohen 2002, p. 8). Even the other extreme, a planet way too close to its star, could have habitable conditions. Imagine for a moment if Mercury were tidally locked to our sun, (something we once used to think but then found out it rotated three times around its axis every two revolutions around the sun). One side would be infernally hot and the other permanently engulfed in cold darkness. Between these two unchanging extremes a gradient would span and inevitably at one point of this gradient a permanent ring would form around the planet on which, with enough air pressure, liquid water and life as we know it could exist… while at the same time farther away Venus would still be inhospitable (Cohen 2002, p. 131). So much for goldilocks zones…

At this point we might discuss what sources we should consider, as there is of course not just the book but also the documentary and its accompanying material. Bizarrely one of the most informative sources I could find about Darwin IV was of all things the brochure to my DVD of Alien Planet. I scanned a part of it here:

Now the first thing to note is that the orbital image here directly contradicts what is stated in the book, as Darwin IV is depicted as an S-type planet orbiting only one of the two stars and Darwin B is shown as similarly sized to Darwin A while also orbiting it at a significant distance. This makes little sense in the context of both the book and the documentary. The length of a Darwin IV-year is also given as 1.6 times that of an Earth-year, while in the book it is stated as being 2 Earth-years long (p. 12). The information given here should therefore not be taken as seriously as our main sources… which is unfortunate as the brochure also gives us information about three things which are not stated in either the book or documentary: The planet’s age (around 2 billion years old), density of the atmosphere (2 times that of Earth) and solar energy received (79% that of Earth). Especially the age and atmospheric density are pretty important, which makes it frustrating that they only come from an unreliable source. I will therefore treat these as estimates, but not necessarily canon. Also interesting is that we get a glimpse of planets Darwin I-III, all apparently larger than Darwin IV. Darwin V and VI are either outside the picture or do not exist in the documentary’s canon. Perhaps they got Pluto-ed.

One dense motherf...

Let us come to the orbital details and geophysics of Darwin IV itself.  As mentioned, going by the book’s information, a full rotation of the planet around its two stars takes about 2 earth-years, so about 730 earth-days. A single day on Darwin IV lasts 26 hours and 42 minutes (p. 12). A Darwinian year therefore lasts about 656 Darwin-days. This is comparable to Mars, whose days last 24h39min and whose year is about 1.8 times as long as that of Earth.

Fig. 4: Physical characteristics of our inner rocky planets. Darwin IV has similar dimensions as Mars, but might internally be structured more like Mercury.

A further similarity between Mars and Darwin IV is that they are small compared to Earth. Earth has an equatorial diameter of about 12’756 kilometers, Mars one of 6792 km and Darwin IV one of 6563km (p.11). This translates to respective volumes of 1.08321 x 1012 km3, 1.6318 x 1011 km3 and 1.48015 x 1011 km3. In other words, Darwin IV has about 51% of Earth’s diameter and only 13.6% of its volume, while sharing almost 97% of Mars’ diameter and 90.7% of its volume. From that we would assume that Darwin IV has a similar mass and density to Mars and therefore also a similar gravity. Gravity is usually measured in gravitational acceleration, which on Earth measures about 9.8 m/s2 (1 g) and on Mars 3.72 m/s2 (0.38g or 38% of Earth-gravity). Now, directly from the text, the gravity of Darwin IV is described as being 60% that of Earth (p. 12), which would mean it has a gravitational acceleration of about 5.88 m/s2. Here we meet our first major mystery. How can Darwin IV be smaller than Mars yet have considerably higher gravity? This must mean it has a higher mass and, due to its size, a way higher density. We can determine the mass of Darwin IV if we multiply its gravity acceleration (5.88) with the radius squared (32815002) and divide this by the gravitational constant (6.673 x 10-11), giving us a value of 9.48858 x 1023 kg. That is about 15.9% the mass of Earth but over 146% the mass of Mars! If we divide this mass through the volume of the planet (1.48015 x 1020 m3) we get a density of 6410.55 kg/m3 or 6.41 g/cm3. That is higher than the density of the Earth, which measures only 5.51 g/cm3! Coincidentally Earth happens to be the densest object in our solar system, meaning Darwin IV is denser than any of our planets. The closest analogy we could compare it to is the planet Mercury. Despite being a lot smaller than Mars, Mercury has a density close to that of Earth with 5.43 g/cm3, making it the second-densest object in the solar system (if we correct Earth’s value from gravitational compaction, Mercury would actually be number 1). The hypothesized reason for that is that Mercury’s inner iron-rich core must make up around 55% of its volume, compared to Earth’s which only makes up 17%. The safest assumption is therefore that Darwin IV’s core makes up a similar proportion of its volume. Determining the exact radius of this core and the rest of the planet’s internal structure is however difficult without having seismological data as we have for Earth. A more pressing question is perhaps how Darwin IV ended up with such a proportionally large core. Three proposed explanations exist for Mercury’s situation:

  • Mercury used to be larger in the past but a giant impact early in its history stripped off much of the crust and outer mantle, leaving only the planetary core and little else behind.
  • Due to its proximity to the sun the lighter elements of Mercury’s outer layers essentially vaporized and then were stripped off the planet by solar wind.
  • During the formation of the solar system, the solar wind of the proto-sun pushed away low-density material from the innermost orbits, leaving Mercury with only high-density material to form out of.

Current surface-data obtained by satellites does not support the first two hypotheses, leaving the last one as the likeliest. Darwin IV is however too far away from its suns for hypotheses II and III to work, unless maybe the planet used to be a lot closer to its parent-stars in the past but then wandered farther out. Such behaviour has been proposed for gas giants, but does not seem likely for rocky planets, so we may assume that Darwin IV formed at roughly its current position. The possible explanations we are therefore left with are either a giant impact or the possibility that planet-formation around F-type stars simply does deal with denser materials than we are used to in our G-type system. I unfortunately could not find any sources about the latter topic, though the higher energy output of F-type stars might result in denser material at farther distances than is normal for our system, meaning a modification of hypothesis III could still work. All that said, the best guess for our subject so far is the impact-hypothesis. The best evidence we might have for it are Darwin IV’s two moons. Not much is said about them, but we can see both of them in the Darwinian sky on plate XXVI (p. 136.) and on the original edition’s cover. Unlike the two moons of Mars, Phobos and Deimos, the Darwinian moons (let us call them Wallace and Lamarck because why not) appear perfectly circular in shape like our own moon. This means they both have reached hydrostatic equilibrium or in other words have enough mass that gravity squishes them into spheroids. The smallest known object with hydrostatic equilibrium is the dwarf planet Ceres, so the moons must be at least that massive. However, since Ceres is mostly made of ice and the Darwinian moons are (probably) mostly made of rocks, it means they are likely considerably heavier. That is a suspiciously high amount of mass in Darwin IV’s orbit. It is not impossible that these moons used to be dwarf- or proto-planets that Darwin IV captured with its surprisingly strong gravity, but you probably guessed what I am getting at here. It seems just as plausible that during its formation a younger, larger Darwin IV was hit by another proto planet, just like Earth was. This impact would have however been considerably more violent than ours, stripping away much of the outer layers of the planet and scattering them into orbit where the debris could develop into fully fletched moons. This impact, perhaps in combination with a higher density of the impactor, fusing of the two cores and/or a generally high density of the Darwin-proto-planetary-disk, led to the formation of the current small and dense Darwin IV.

Fig. 5: The two moons of Darwin IV as seen from its northern tundras.

With these assumptions we will then move on to part 2 where we will examine the geography, geology and atmosphere of the planet. Thank you so much for reading and see you until then.

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Related Posts:

Literary Sources:

  • Barlowe, Wayne: Expedition. Being an account in word and artwork of the 2358 A.D. voyage to Darwin IV, New York 1990.
  • Barlowe, Wayne: The Alien Life of Wayne Barlowe, Beverly Hills 1995.
  • Cohen, Jack/Stewart, Ian: Evolving the Alien. The Science of Extraterrestrial Life, London 2002.
  • Costard, François/Forget, François/Lognonné, Philippe : Planet Mars. Story of Another World, Paris 2006.
  • Grinspoon, David Harry: Venus Revealed. A New Look below the Clouds of our Mysterious Twin Planet, Cambridge 1997.


Online sources/Further reading:

Image Sources:

  • Fig. 1: Barlowe 1990, cover.
  • Fig. 3: Wikimedia
  • Fig. 5: Costard 2006, p. 24.
  • Fig. 6: Barlowe 1990, p. 136.