The Real Callisto
Jondar and Lankar's Callisto
Understanding the Anomalies
The Geography of Callisto
It's turning out that pretty much every planet and moon that we look
at in our solar system is not only strange, but stranger than we expected.
That's a lot of fun, actually.
The real Callisto
appears to be a pretty quiet place at first, mostly rock and ice.
But its got some surprises. It is almost the size of Mercury,
at 2985 miles in diameter, but has only a third its mass. Its density
is low, approximately twice that of water ice (Water Ice is 1.0.
Callisto is 1.86. For comparison, Earth is 5.6), which suggests that
more than half its volume is ice, with the rest being rock and slush.
Its surface gravity is only 12% of Earth's.
There's little or no evidence of an active internal core (the low mass
would argue against that) or of substantial geological processes.
No volcanoes, no mountain ranges, no deep fissures. Mostly, its craters,
with a couple of really big ones. The biggest, Valhalla, is 600 miles
across with impact rings produced by the shockwave 3000 miles in diameter,
the second biggest is Asgard, at about half that size.
Although it's the darkest of the Jovian moons, its still twice as bright
as Earth's moon. It's got a whispy atmosphere of Carbon dioxide.
It has an orbital and a rotation period of about 16 days, meaning it always
keeps the same face turned towards Jupiter. There's some evidence
for a slight magnetic field, and perhaps possibly a buried liquid water
ocean or sea (which might be producing the weak magnetic field).
But those tantalizing hints aside, mostly, it's cold, dry and geologically
and Lankar's Callisto
Carter's Callisto, as given in his novels, is a little bit smaller than
the real one with a diameter of about 2770 miles. I suppose
I could have adjusted it up to match the real world, but there are so many
other differences that it seemed pointless. But anyway, let's take
a few minutes out to work out some of the physical dimensions of our planet
Starting with a diameter of 2770 miles, we get a surface area of about
24 million square miles. Now, this amounts to only about half
the roughly fifty million square miles of Martian surface, and one-eighth
of the two hundred million square miles of Earth's surface.
But remember, that in the case of Earth, only about a quarter of the surface
area is land... This means that Callisto's surface, by itself,
is roughly as big as Asia and Europe put together. It's also about
twice the surface area of the moon.
What this means is that there is plenty of space to have adventures
on, particularly since most of Callisto is land. There are
only five large bodies of water: The two polar caps and adjacent
mountain glaciation, two seas (the Corund Laj and Sanmar Laj) and a large
lake (the Cor Az) on the 'dark side', collectively accounting for perhaps
20% of the surface area.
Of course, 'known' Callisto, at the start of the books is mainly the
'light side,' so theoretically, we'd cut the surface area in half.
But that still gives us a volume of land half again the size of North or
Callisto also has a circumference of about 8700 miles. That's
roughly three times the width of the North American continent at its midpoint,
or a hell of a walk. A circumference is a complete circle of the
planet at its widest. Normally, you wouldn't walk in a complete
circle. But this means that the farthest place away from you
from anywhere on Callisto is going to be 4,350 miles away (the farthest
point on the circle, after that, it gets closer and closer as you round
the circle and return to your starting point). Still a pretty
damned good walk.
We also get a volume of 11 million cubic miles. Roughly,
that's three times the volume of the moon. One quarter the volume
of Mars, and one twenty-fourth the volume of Earth. Put another
way, you could fit three moons into Callisto. You could fit
four Callistos into Mars, and twenty-four Callistos into Earth.
For the record, you could get sixty-four moons into Earth and eight Mars
into Earth. Why is that important? We'll get back to it later...
Carter's Callisto has a surface gravity that is substantially heavier
than Mars or the Moon. John Dark, arriving, notes that the
gravity seems earth normal. Later on, in a fight, he discovers
that the lower gravity actually gives him a significant advantage in strength
over the locals. So.... Not too noticeable, but enough
to make a real difference? Perhaps 80% of terrestrial gravity,
at a guess?
This suggests that Carter's Callisto is at least seven times heavier
than the real one, and proportionately two and a half times heavier than
Mercury. In turn, this would probably have an effect on Callisto's
own orbit, and on the orbits of the other Jovian satellites.
In part because of the higher gravity, Carter's Callisto also has a
substantial, 'Earth thickness' and 'Earth composition' atmosphere.
John Dark is pretty close to sea level on Earth when he transports through
space. Arriving on the new world, he doesn't seem to be short
of breath, which tells us that composition and density of the atmosphere
must have been pretty comparable.
This Callisto is unaccountably bright and hot. As recorded
by Dark, it seems that the sky is luminous. The sun is so far away
it is practically a bright star. Jupiter and the satellites contribute
some light, but not that much. Yet Callisto experiences atmospheric
light equivalent to terrestrial daylight, which shuts off on a regular
basis, giving us a 'day/night' cycle. Moreover, the satellite is
warm enough that it has temperate or rain forest climate over much of its
volume. Only at the north pole does it get cold enough to form ice
This is very peculiar. It appears that the moon is generating
more light than it receives, which should make it a very very bright object
from Earth's point of view (unless there is some means by which Callisto's
light is hidden).
The source of the extra heat and light is a mystery which Carter never
adequately explains. When pressed, he mumbles something about
'electrical excitation' of the atmosphere, postulating some upper atmosphere
'neon' layer that gets all charged up by solar radiation or Jupiter's magnetic
field or something. Then his character changes the subject.
That's perhaps not unacceptable, since his character is an adventurer not
a scientist. The whole point is just to have a setting to tell the
story, not to justify it. So, that leaves it up to us, I guess, to
try and make sense of it.
The point is that this Callisto is so radically different from the real
world jovial moon, that those differences -- mass, gravity, light output,
heat, atmosphere, etc. -- would be readily apparent from Earth.
In essence, Jandar's Callisto is most definitely not in our Universe.
But if not ours, then whose?
Okay, let's take it as a starting point that this Callisto is very different
from ours. What is the key difference? Gravity,
I think. Gravity is a lot stronger on this Callisto, approximately
seven times stronger, and very near earth standards.
The gravity means that Callisto has to have a lot of mass.
Well, Callisto isn't anywhere near Earth, or even Mars sized.
Its volume, as we've noted, is pretty puny. This means that it has
to be much denser than the real Callisto, which is basically a dirty slurpee.
The real Callisto's density is about 1.86, about twice as dense as ice
(1.0). Earth's and Mercury's, the two densest large bodies in the
solar system, is around 5.5. Mars density is about 4.0. (By
the way, Mercury's greater density is why its gravity is almost as great
as that of Mars, despite being a smaller body).
For Carter's Callisto to have the gravity it does, it needs to have
a density which is off the charts. Somewhere in the vicinity of 12
to 14. That's pretty extreme, in fact, its damned near insane.
Earth's composition is pretty heavy, about 35% iron, with a mix of oxygen,
silicon, magnesium making up most of the rest. Callisto's makeup
has to include a lot heavier stuff, and a lot more of it. Probably, instead
of iron, as with Earth, Callisto's inner core is lead, which is four times
heavier. It's likely that the core also contains a fair number of
volatiles, like Uranium, Plutonium, Radium, etc., in greater quantities
than Earth, which makes Callisto a very 'hot' world indeed, far hotter
than its mass would normally be. It's also likely that the
tidal stress of being one of Jupiter's satellites is also keeping the core
Callisto's 'sky-brightness' is attributed to electrical excitation of
the atmosphere. Now, Callisto is standing outside Jupiter's
magnetic field (or at least it is in our universe), and its too far away
from the sun to pick up significant radiant energy, so the only source
for this excitation has to be Callisto's own magnetic field.
Earth's magnetic field is a doozy, yet the best it ever manages is the
Aurora Australis and Aurora Borealis, or the Northern and Southern lights,
when a strong solar wind comes along. Sure, its pretty as hell.
But it's a candle compared to the daylight conditions produced by Callisto.
Lead doesn't produce electromagnetic effects. It's pretty inert.
So this tells us that Callisto's heavy, extremely hot, lead core is heating
up and rapidly spinning a molten outer of iron, which also adds to the
moons mass and generates the powerful magnetic field that lights up the
sky and keeps the surface warm.
The large dense inner and outer core then gives way to a relatively
thick, rocky mantle and crust. I say relatively thick, because we
see no sign that Callisto is a swamp of magma and erupting volcanoes.
So there has to be a thick insulating layer of rock for the surface to
be as stable as it is.
It is likely that the iron outer core is spinning much faster than the
planet's surface. It may well be spinning faster than the lead inner
core. So, this suggests that the inner and outer cores are
not tightly bound to the mantle, but rather, are probably sitting surrounded
by a liquid rock mantle layer, which acts as an interface between the inner
and outer spin rates.
There may be several distinct mantle layers, and its likely that Callisto's
internal structure is even more highly defined than Earth's. One
thing is clear, this volatile internal geography is not showing up on the
surface as plate tectonics or outbreaks of volcanoes. The few
mountain and lowland areas show no sign of continental structures.
This means that whatever is going on under the surface, the crust seems
to be relatively stable.
If Callisto's heat and light are the by-products of a turbocharged spinning
iron outer core, then it may explain why the areas of the magnetic poles
are so cold and dim, differing climactically from the rest of the planet...
Although intuitively, I might have expected them to be the brightest and
hottest spots on the planet.
As to why the light seems to have a day/night, on/off cycle, I can't
say. Possibly, it's some issue with the atmosphere or potentially,
the iron core has some sort of cycle. Conceivably, the day/night
cycle is not continuous over the planet, but is constantly occurring in
Those problems aside, this does much to explain Callisto. But
it does pose some new issues. For one thing, if Callisto was
this magnetically active, it would blare like a siren on radio telescopes,
which would make it even more noticeable in our universe. For
another, it would pose real problems for space travellers.
A magnetic field that strong and erratic might well fry anyone's electronics.
Visiting Callisto might be a one way trip, easy enough to visit, hard to
Geography of Callisto
drew some decent maps of his Callisto, so I'll recommend them to the reader.
In terms of geography, the important factor is that Carter's Callisto,
like the real one, is tidal locked. That is, its rotation and revolution
period are the same, it takes the same amount of time to orbit as it does
to turn around on its axis. As a result, Callisto always keeps the
same face towards Jupiter.
This is significant, because mainstream civilization on Callisto seems
concentrated on the 'light side' or side facing Jupiter. The opposite
hemisphere, the 'dark side' facing away from Jupiter was considered to
be a vast unknown and forbidden territory.
Starting with the 'day side' the most prominent feature is the 'Grand
Kumala' a vast tropical rainforest larger than the Amazon which sits at
the center of the day side. Its surface area is almost four
million square miles, it ranges 500 miles north to south, and 2500 miles
east to west.
The Kumala is bordered on the south by the 'Plains of Haratha'
which appear to be largely unpopulated, though there is evidence of prior
inhabitation (the teleport station/temple). The Plains of Haratha
appear to be semi-arid expanses, like the prairies or Siberian tundra.
The dominant plains animal is the Vanth, a large elk-like herbivore which
migrates seasonally. We assume it is forced to migrate because
local pastures are not resilient enough for sustained grazing.
This suggests a relatively slow growing plant community. Another
notable life form is the walking trees, which move from place to place
in search of moisture. We are told that rain is both infrequent
and extremely torrential, a sort of feast and famine hydrology which can
be pretty tough to deal with. The picture that comes to us is of
a stable grasslands ecosystem operating on very limited water supplies.
The plains are grasslands because there isn't enough water to support trees
in most areas. Stands of trees, or clumps of forest probably
represent deep subsurface or subsoil water pockets and aquifers
The plains are likely uninhabited by farmers or cities because the poor
soil and limited water will not support intensive agriculture.
However, from the teleport site ruins that there was once at least one
substantial complex, perhaps a city, in the region. Perhaps several
cities. It is possible that there was once a wave of agriculture
on the plains, perhaps sustained by fertilizer and irrigation, which eventually
failed, ending that experiment.
South of Haratha, we come to the south polar region. Like the
north pole it is described as cold and frozen, we have evidence of glaciation
on the subpolar black mountains, so it's likely a glaciated region.
It is not clear why this should be so. On Earth, the poles are cold
because they get the least amount of sunlight. Callisto's heat and
light are internal, so there seems to be no good reason at the outset why
they should get less, or why light and heat are not evenly distributed.
On the north side, there are the 'White Mountains.'
And directly above that we get to the frozen wastes and eventually the
north pole. The northern polar area is definitely cold and
is referred to on maps as 'frozen lands.' An inadvertent visit
in Sky Pirates of Callisto confirms this impression.
On the northeast,
there is a fertile plain fed with several large rivers which apparently
drain from mountains or from the jungle into the Corund Laj, a name which
translates to 'Greater Sea.' It is the largest body of water on Callisto,
with a surface area of perhaps two to three million square miles.
It may be that part of the size of the Corund Laj is due to the fact that
it seems to be a drainage basin for much of the northern hemisphere, all
water eventually winds up in it. This suggests that a large
part of the Corund Laj may be very shallow, and it accounts for the fact
that it contains one significant island.
The southern hemisphere water body, is the Sanmur Laj or 'Lesser Sea.'
It is perhaps half the surface area of the Corund Laj. Unlike the
northern sea, the Sanmur Laj does not appear to sport much of a drainage
basin, there are no substantial rivers which drain into it.
There is some evidence that it is slowly shrinking, there is a large lake
adjacent which appears to have once been part of it. The Sanmur Laj
is likely a saltier and generally deeper sea than the Corund Laj, with
fewer shallows and is probably less biologically productive. It is
believed to be the home of the Laj-Thad or 'sea people.'
As an odd coincidence, we've already noted that the real Callisto has
two huge impact basins, Valhalla and Asgard. These two are about
the right size to be the Corund and Sanmar Laj. Given that
there is no way Carter could have known about these impact basins, much
less incorporate them, we can chalk this down as yet another of these strange
coincidental overlaps. In any case, I don't think that the
seas are impact basins, I suspect that they have a more interesting explanation.
West of the Sanmar Laj are the Black Mountains, in which the Yathoon
have their hidden valley, located in the only known geologically 'hot'
region on the planet. The geology of both the Black and the White
mountains produces the strange buoyant gas which floats Thanator's airships.
On the opposite
side of Callisto, the forbidden and unknown 'dark side' or 'far side'
there is a large and largely unexplored southern plain, and three interesting
sets of features. Proceeding from the light side, the first
area is the hill/mountain complex ruled by the Zarkoon, a race of winged
cannibals. Past that is a vast plateau ringed by mountains,
which contains a huge lake, the Cor Az. And then beyond that,
connecting to the Cor Za by a river, is the Harangzar mountains and valley.
These three features appear to be loosely connected as a band of mountain/hill
North of this area is a plain designated as 'unexplored' and beyond
that, are indications of a small unnamed mountain range. Aerial
flyovers indicate that it is inhospitable grass and scrublands.
One observation which can be made with respect to Callisto's mountain
areas, is that there doesn't seem to be any evidence of tectonic plate
activity as seen on Earth. On Earth, mountain ranges are shaped
by continental plates moving against each other, and so there are recognizable
patterns of ranges and volcanoes. None of this is present here.
The mountains are just clumped in groups, the seas and lowlands, the highlands
form no discernible plate patterns. We cannot trace the outlines
of continents or continental plates anywhere on Callisto, the way that
we can do on Earth..
This is likely because, despite its heat and mass, Callisto is a much
smaller world. Or possibly, its outer crust is comparatively thicker,
allowing less actual movement. However, the absence of tectonic
plates means that other reasons will have to be found to explain Callisto's
mountains and lowlands.
Generally, the Dark Side seems to be dryer and more impoverished, geographically,
than the Light Side. This is probably an effect of the tidal
lock. On Earth, the lunar tides from a comparatively weak moon cause
large lifts in water as the Earth spins. On Callisto, the gravity
of Jupiter is far greater, and Callisto always keeps the same face to Jupiter.
So, what this means is that moisture will probably tend towards the
day side, with the Grand Kumala rain forest being the result. This
doesn't mean that the dark side will be all desert, after all, it's all
one planet, and a small one at that.
Given the gravity, clouds and wind and moisture are going to circulate
right around the planet. However, there will be more tendency
towards rain forest on the light side and arid conditions on the dark side.
This explains why the most fertile or wettest and most biologically productive
regions on the dark side tend to be sheltered within mountain complexes.
And it also may explain why human civilizations tend to be concentrated
on the light side, where presumably, there is more water and more biological
productivity, even outside the rain forest.
The placement of the two seas is interesting and perhaps key.
They are literally on opposite sides of the planet from each other, in
the northern and southern hemispheres. We've seen with Mars/Barsoom
that features on diametrically opposite sides of the planet can be related,
thus the Hellas Impact basin seems to correspond to the Tharsis uplift
region, and the Argyre Impact basin appears to relate to the Elysium volcanic
complex. In the Martian case, these areas are the result of
titanic impacts which flattened one side of the planet and whose shockwave
ruptured the opposite side.
Here, unlike Mars, what we have, however, is two related depressions.
So its unlikely that an impact was directly responsible. If it had
been, we would have noticed an uplift area and a sea, not two seas.
So, what's going on here?
I think these seas are the sites of fossil poles.
Bear with me. Planets and Satellites spin on their axis, right?
This means that centrifugal force invariably moves mass towards the equator,
with the result that the planet or satellite is wider than they are tall.
Gravity works to keep it basically round, but the effect translates into
a slight flattening in the polar areas. In a nutshell, the
polar areas tend to be a slightly or somewhat lower elevation than the
rest of the planet. They're not actual basins, but they are
sort of depressions.
So, let's say that early in Callisto's history, after the crust has
solidified, but while it's still somewhat flexible, its spinning along,
minding its own business. Then, all of a sudden something very big
comes along and whacks it. Something perhaps on the scale of
the Argyre or Hellas impact. Callisto is a smaller world, and it's
locked in a perpetual gravity struggle with Jupiter, so it's a bit less
stable than Mars. It doesn't fall out of orbit or anything
like that, but what does happen is that it wobbles off its axis.
Or more accurately, the axis drifts away from the established poles and
re-establishes itself approximately 35 to 40 degrees away.
Now, this causes several interesting things to happen to the young planet.
Obviously, its not made of silly putty, so it doesn't just reform smoothly,
with the new poles flattening out and the old polar regions assuming a
more rounder shape. On the other hand, we can assume that the moon
is still relatively young. And the new axis is going to put sheering
pressure on the world's geography.
The satellite's geography becomes stressed. The old polar
lowlands, now 45 degrees off and spinning on the sides of the moon are
subject to sheering or lateral stress. They deform, becoming
elongated, east to west, with the direction of spin, and narrowing north
to south. They're pulled from roughly circular lowlands or flat lands
into distorted oval shapes.
In turn, the deformation of the former polar regions east to west affects
the local geography. After all, if you are stretching out the
former polar basin, then lands beyond that basin have to go somewhere,
and it uplifts into mountains or highlands. If we look at the
map, we find mountainous regions on both the east and west sides of the
Corund Laj, and a mountainous region opposite the Sanmur Laj.
In essence, we are finding mountains where we would expect to find mountains
if the polar lowlands were moved and deformed.
Finally, the deformation of the old polar regions would tend to produce
relatively flat table lands towards the equator in each case.
Moving east and west, the deformation pushes up lands into mountains.
Contracting north and south, the same process will 'pull down' mountains,
giving us flat plains, riven with chasms and canyons. This
is actually a pretty good description of the plains of Haratha and the
Okay, so the question is, if something did hit the planet that was big
enough to tilt it off its axis, that's a pretty big goddamned hit.
So where is it? And as we've seen with Mars and Mercury, a hit that
big is likely to mess up the opposite side of the planet... So where
is that? We need at least one major impact site, perhaps two.
Can we find them?
Oddly, yes. If we look at the dark side, there appear to
be two strange features which may represent the remains of titanic impacts.
The first is the region of the peaks of Harangzar, a roughly circular or
oval mountain formation which encloses a large valley containing the haunts
of the Mind Wizards, and their forbidden city, Kur.
The other is the plateau of Cor Az, a strange circular area.
Strange because it isn't a crater per se, but rather a plateau.
The plateau sort of an elevated crater, it's ringed by high mountains,
and contains a large lake, the third largest body of liquid water on the
planet (puny compared to the two seas), which lake drains into the third
largest river on the planet. It's the home of the cave people and
the river people, as well as the home of strange monsters not found elsewhere.
It's also the home of Yllana, the Cave Girl.
The Cor Az is a bit of a puzzler. Normally, it has many of the
characteristics of an impact site, high ringing walls, a shallow bowl within.
On the other hand, the whole region is elevated, and obviously, we expect
impact sites to be depressed.
What we are looking at, I think, is a pair of impacts, which are closely
related, perhaps occurring within months or years of each other.
The Cor Az impact comes first, and whacks the moon hard enough to make
it ring like a bell. Under normal circumstances, that would
be it, the Cor Az becomes a big depression, some mountains spring up on
the other side, and Bob's your uncle.
However, immediately (in geological or astrophysical terms) after the
Cor Az impact comes the Harangzar impact, while the moon is still in a
fluid state from the first impact.
The Harangzar impact depresses the crust underneath it, while pushing
up the crust around it, much the same way that pushing down on one spot
on a waterbed will cause the area around that spot to push up.... No big
deal that, we saw the same thing with the Hellas impact on Mars.
However, in this case, the most vulnerable and 'pre-fractured' turf is
the Cor Az impact area, where the crust has already been deformed and broken.
So this area is pushed up to become a plateau.
The shock fractured crust also produces an uplift mountain area on the
opposite side of the plateau, which becomes the hangout of the Zarkoon.
The process is fairly simple. Cor Az hits, fracturing or impacting
the crust. Then Harangzar hits, pushing the compressed Cor Az impact
basin straight up into a mighty plateau. However, Cor Az settles
back a bit, descending most around area of greatest compression, the impact
basin. The result is the ringing mountains get higher. But
as Cor Az sinks from its peak, material has to go somewhere. So the
Zarkoon volcano/mountain complex forms on the opposite side of Cor Az,
along the fault line produced by the two impacts. It's all
in a straight line.
And if we look at the opposite side of the planet from Cor Az and Harangzar,
what do we find? The White Mountains, a geologically unique place,
home to the mightiest mountain ranges on the moon, and principal source
of the lifting gas of Zanadar. In short, a strange, disordered mountain
territory, exactly where it should be.
The White Mountains are also to the west of the Corund Laj, so the deformation
of the former polar regions may also have contributed to their formation.
But that's okay, we're allowed to have more than one process acting to
create the same mountains. So, the geography of Callisto is
actually starting to make a pleasing amount of sense.
Of course, this begs the question, did Lin Carter have any of this in
mind when he drew his world up? Sadly, probably not. He's dead,
so we can't ask him. But my own thinking is that he probably didn't
think it through like this. He wanted a big jungle, so he stuck
that in the middle, thought some seas would be good, so he tucked them
in, and then some mountains had to go somewhere, etc. So really,
it may have amounted to no more than doodling.
On the other hand, he was not a stupid man, he was well aware of Earth's
geography, and almost certainly had some smattering of geology. Plate
tectonics, for instance, would have been well known to him, as well as
the relationship of mountain ranges to cloud movement and water drainage.
He would have had examples to draw from, even if he didn't fully understand
the processes that created these examples. So its likely that in
his world building a certain amount of conscious and unconscious expertise
or insight went into it.
But whether he worked out the process to the same level of detail I
So why do I bother? Well, because its fun, and because I can.
It's a fun challenge to take something like this and try and make it make
sense, to take a picture and work out the history of that picture.
Hopefully its at least mildly entertaining to you, the reader as well.