Archive for the ‘Chott’ Category

Your Turn, Round 1-2: In Which Michael Designs Aliens

The role-playing scenario, called “The Farthest Star“, that I set on Chott follows a classic theme: the robinsonade or desert island story.  Rachel would call it another iteration of The Conversation That Never Dies, since it is centuries old.  Plainly spoken, a group of humans – be they the original Robinson Crusoe, a Swiss family, a bunch of primary school students, or some other ragtag bunch of misfits – are put somewhere isolated and have to survive.

This is a remarkably diverse premise.  That’s why the general theme is so popular.  Put humans from the present in the past and we have alternate history.  Put humans from Earth on another planet and we have science fiction.  Setting this on Chott gives a fun scenario for the players to play through, and a chance for me to show off my worldbuilding.  But I couldn’t just make the map.  I had to populate Chott with interesting things and characters for the players’ characters to encounter and deal with.  And now you all get to rip my designs for alien biologies and societies apart.

Sufficiently Advanced Aliens

I needed a way for present-day humans to get lifted from the Earth and dropped onto Chott.  To do that, I used a technology that was functionally indistinguishable from magic.  Like Greg Benford, I invoked the perhaps-not-entirely-impossible concept of negative mass,  where the gravitational and inertial masses are of opposite signs.   I defer to someone with more expertise in theoretical physics to tell me if negative mass is possible or if it violates one of the fundamental symmetries of the universe.

I also assumed negative and positive near-point masses under very sophisticated and intelligent control, be they somehow-stabilized specks of neutronium or black holes just big enough to not put off too much Hawking radiation.  Putting a negative point mass next to a positive point mass gives an engine: the positive mass is attracted to the negative one by gravity, but the negative mass is repelled.  Or the other way around, depending on which of the negative mass’ masses is negative.  Either way, the dipole then goes flying, and it can be loaded down with a payload of conventional positive-mass non-degenerate matter.  Conservation of energy has to hold, so I decided that the dipole sucks energy out of the local expansion of the universe – effectively, slightly pulling space closed behind it.  Momentum would be conserved by gravitational wave radiation.  This thing has a strange wake.

While the acceleration of the point masses and their payload can be also arbitrarily high, it can also be compensated so that the abducted humans are not turned into highly-compressed organic goo.  All of this was assumed so that characters from present-day Earth could be flown across most of a kiloparsec in a few subjective hours.  But who’s flying this strange starship?

I called them the Examiners.  They are never seen directly, interacting with the humans only by an AI avatar assigned the job of testing humanity by abducting a sample of several hundred and dropping them on Chott with a certain amount of equipment for a bit over a century, to be observed without any interaction until the end of the test.  What a galaxy-cluster-spanning billion-year-old sufficiently-advanced culture would learn by spending five and a half millennia  playing with six hundred apes was not specified.  Maybe it tells them something useful about properties of human culture that don’t vary over centuries.  Maybe the Examiners are just being cruel.  Maybe they operate on some inscrutable alien agenda.  Maybe the Examiners themselves are a million years dead and the humans are dealing only with the AI.

Either way, the Examiners exist as a way to set up the robinsonade.  Their emissary picks up the humans, explains the situation to them, gives them several hundred tons of custom-built equipment, and drops them into a playa on Chott, telling them to survive and thrive for the next 121 years.

The History Of Chott

Chott has been used by the Examiners for testing for the last few million years, for anyone who is able to breathe the air or/and drink water with some mixture of dissolved ions.  Humans are simply the most recent ones to arrive.  The planet is quite liberally dusted with ruins left behind by the previous testers, concentrated into the areas that the Examiners found most suitable for dropping them in.  It’s also dusted with microbes and some larger lifeforms from many different worlds, although those that are not Chott-native have a tendency to get out-competed and eventually die off.

In the last few tens of thousands of years, five tests have taken place in one particular longitude range in Chott’s southern temperate zone.  The humans encounter what the previous four groups left behind.  The ruins provide various resources for the humans to use, as well as information about the people who lived in them.  I had only called them T-1, T-2, T-3, and T-4, going back in time from the most recent to the least recent.  The players promptly named them treants, snakes, tetras, and hexes.  So I’ll use those names here.  Everything will be referenced to the time when the humans arrived at Chott, which is sometime in the 4700s CE on Earth.

Here’s a map of a section of the south temperate zone of Chott.   The humans arrived at the point labeled “Drop”, and rapidly surveyed this area using UAVs that the Examiners had provided to them.  T-1 marks the range of treants ruins; T-2 where the snakes are buried; T-3 and purple dots tetra sites, and T-4 marks the hexes.  Earlier testers on Chott were outside of this region.   Darker-colored regions are generally raised. The lower-right area is volcanic mountains; the upper-left is a rift valley. In between is the ocean and the lower, light-colored playas. The lakes in the playas are colored green but are a varying mixture of different colors due to all the different algae- and bacteria-like things growing in them.   MB: Thanks to Rachel for the picture as opposed to my pencil-sketch.

The Treants

The treants were tested about three thousand years ago (which means that the AI in charge of testing the humans didn’t know about the treants’ test before it picked up the humans, but was informed en route).  Like humans, they are a low-salt species and could not drink Chott groundwater.  They constructed a network of large solar-powered stills on the high ground around two adjacent playas to provide themselves with water, several of which the humans in both runs of The Farthest Star renovated to use themselves.  Unlike humans, the treants look like something from a cross between an elephant and an oak tree, with tentacles instead of arms and side-mounted protruding eyes.

The treants had somewhat different technologies than humans.  Not necessarily less advanced, but different.  Their chemical engineering was good.  They managed to power their vehicles using plant-derived hydrocarbons and built the roofs for the stills to last through over five thousand Chott storm seasons.  Their medical science was well-developed as well.  They were not used to Chott’s gravity; it was too high for them.  So infant treants had prosthetic legs to help support them, rather than immediately being able to walk.  But the treants did not have large-scale heavier-than-air flight, and so did not explore the entire planet.
The treants fought a brief civil war a few decades after their arrival, over disputed water and food rights.  It ended with a low body count, and did not appear prevent them from passing the test.  Or so says a book the treants made, printed on metal sheets and left in their library just before the Examiners returned to take them all home.


7000 years ago, the snakes were dropped at the south end of the playa that would later host the humans.  They could have handled the salinity, but did something very foolish and set up a single initial camp underneath an unstable slope.  The entire group was buried under a landslide.  There were no survivors.  I confess that such an extreme failure of judgement seems unlikely.  I had it have happened to demonstrate to the players that failure was possible, and that I would let their characters die if they did something equally unadvised.

The snakes were only snakelike in their method of locomotion.  The rear halves of their bodies were elongated, flexible, and with a series of friction pads on the underside.  The front halves of the bodies were held upright, allowing appendages to more easily manipulate objects and for the eyes to give a better view of the surroundings.  If you squinted hard enough at the partial reconstruction of one of the bodies by the humans, it looked something like a rearing cobra.  Hence the name.

It did not come up much in the run-throughs of The Farthest Star, but some of the snakes’ equipment could have been salvaged and used by humans.  It included ceramic-shelled tents, crushed flat but with individual sheets of ceramic composite (based on alumina and corundum) that were still intact.  Had the humans started fighting one another, those would have been useful as improvised ballistic armor.


The tetras were a hive mind intelligence, composed of specialized tetrahedral elements that joined to each other by clasps at the vertices that also conveyed the equivalent of nerve impulses.  Some were primarily structural members, some muscle, some sensors, some manipulators, some reproductive, some processing, and some data storage.  As confusing as it may be to think about, when they were networked, the processors automatically pooled into a distributed shared awareness that could break apart and recombine at will.

We can call the tetra units that the Examiners brought to Chott either “it” or “they”.  Either way, the tetras established a central base about 2000 km to the west-north-west of the human, treant, and snake centers.  Smaller subsidiary minds were sent out to explore; a plane carrying one of them crashed and was later partially excavated by the treants and then studied by the humans.

The tetras had no concept of reading or writing at the beginning of the test, although they did understand communication between separate minds by pressure waves and radio.  They did attempt to communicate with later testers by leaving individual memory elements at various hex ruins.  But after seventeen thousand years, their biological solid-state storage was completely decayed.  So the humans could not even attempt to understand what exactly tetras thought.


The hexes were six legged and salt-loving.  And they were very good biologists as well as thorough explorers.  30,000 years ago, they explored the entire planet and studied the remains from tests as far back as 350,000 years ago.  They attempted to ensure that their ruins would be noticed by future testers and that those testers would know who they had been.
The hexes built three monolithic hexagonal-prism towers at a place the humans called Triangle.  They could be entered only from airlock doors on the roofs.  Solar-powered crystal radio beacons announced their presence to anyone with a receiver within a few hundred kilometers.  Inside were thousands of square meters of microprinted cave paintings, developing a common vocabulary and working up to give a description of the hexes’ history on their home planet (about 1800 lightyears from Chott and 4500 from Earth) and of everything they had done during their test.  From this, the humans got a crash course in xenobiology – hex and Chott – beyond what they had been able to figure out themselves.  Most of the plants and animals that the hexes had engineered had been taken with them or had died out and could only be identified by remains, but some were still alive on the surface of Chott.

The Rollers

One of the things the hexes engineered was a species of wheeled animals to hunt down and eat predatory Chott-native species.  The wheeled design was quite efficient on for moving on the playas, and a rocker-bogie arrangement allowed them to ascend fairly steep and rough terrain.  The wheels were biological stepper motors, with small muscles controlling samarium-cobalt magnets on the inside of each wheel.  Another set of magnets and the rims were separated from the hubs by something that could be called blood.

The hexes made the rollers intelligent enough to hunt in groups and to use the simplest of stone tools, to make them more efficient hunters.  Protoculture technique-sharing and vocalizations from deliberately grated wheels completed their initial skills.  Reproduction was parthenogenetic.   The hexes controlled the roller population in  two separate ways.    Chemical triggers shut down reproduction in rollers that spent too much time in the presence of too many other rollers.  And the samarium to make wheel magnets required a particular protein to be metabolized and formed into magnets, a protein that the rollers themselves could not produce.  That protein was synthesized by the hexes and provided only in a large mass in the center of one of the hex’s settlements.  The rollers would periodically return to the supply, or they would lose their ability to keep on rolling.

But then the hexes left, leaving the rollers nothing but the large monoliths and pile of the protein at Triangle.

Thirty thousand years passed.  The tetras did not notice the rollers, because its planes did not fly far enough east to enter the rollers’ range.  The treants did not walk that far either and the snakes had no chance to see anything.  The hexes had allowed a relatively high mutation rate and over the five to ten thousand generations between when the hexes left and the humans arrived, the rollers evolved.

Those that were smart enough to hunt effectively on their own – and later, to deliberately spend periods of time by themselves – had more offspring and rapidly dominated the population.  Language and technology both developed soon after.  By the time the first human aircraft buzzed overhead, the rollers had developed a culture roughly analogous to the human late-neolithic or early-bronze age (I was inspired to this idea by the webcomic Schlock Mercenary).  The analogy is limited, since the rollers use salvaged bits of metal from hex ruins for spear-points rather than smelting metal.

Roller culture is distributed, and has expanded to cover a much greater range as the rollers became better at navigation and caching food.  Small groups travel well over a thousand kilometers from Triangle in search of prey.  Social prestige and more offspring come from being a skilled enough hunter to bring down prey alone, usually using thrown spears, or from killing the largest prey in the smallest possible group.  Elders, slowed by age and by injuries up to and including loosing one wheel on each side, are valued for their experience and for the time they can spend caring for and teaching their grandchildren.  And every two chott years, all of the rollers – there are tens of thousands of them – convene at Triangle for a festival that has grown up around the necessity to eat mouthfuls of dirt-of-life.

But the rollers have a problem that they are not yet aware of.  In the beginning, there was a large mound of the dirt, half-buried in the center of Triangle.  Now there is a large pit, with the last few meters of dirt-of-life at the bottom.  If nothing is done, in another few thousand years, the rollers would go extinct.

And so we have plot for the human characters to deal with.

Your Turn, Round 1-1: Chott

This time, we’re going to do things somewhat differently.  I will describe a fictional planet that I created for a role-playing game scenario, which Rachel and a bunch of players on ran through on different occasions.  Then you get to point out anything and everything that I got wrong.

Despite my repeated poking at the economics and sociology of other works, here we’ll just start with the description of the planet and let you all tell me the right way to do planet formation, geophysics, geology, and meterology.  The people and cultures that have lived on it and the plot of the scenario can wait for another post.

Ready?  Here we go.


Chott is a planet with a mass of about 0.5 Earth masses, formed out of material with a similar ratio of carbon to oxygen.  A shortage of oxygen would have meant a mineralogy dominated by carbides or some other more exotic materials rather than oxides of silicon.  While such mineralogies likely occur on some exoplanets, our knowledge of the geophysics and geochemistry for such places is very limited, so I’ve left Chott with near-solar C:O and changed some other things instead.

Chott has somewhat less water and other volatiles per unit mass than Earth or Venus, although it has retained more than Mars.  There is enough water in the crust to keep plate tectonics operating roughly as it does on Earth, with differences in arc volcanism because there isn’t quite as much water-rich subducted ocean sediment.  Mid-ocean ridges do exist, but the rate of spreading is less because there is less geothermal heat to drive the convection.  The lower ocean depth exposes the ridges above the surface of the water, adding to already larger areas of land with relatively little vertical relief.  The rate of orogeny is slower than on Earth, so the balance between erosion and mountain-building is reached at much lower heights.


In part because of the insolation from its host star and in part because of the weaker greenhouse effect from a thinner atmosphere, Chott is colder than Earth.  The polar regions have permanent ice caps, and relatively little water evaporates from the oceans to be rained out on the land.  While there is some groundwater, most streams and lake beds are transient, with the lakes getting water during only part of the year and being salt pans the rest of the time.  This is where I got the name for the place, although I admit to using the word “chott” incorrectly – the rainfall is seasonal, but not necessarily concentrated in the winter.

Over geologic time, Chott’s oceans have become hypersaline relative to Earth.  The lakes are also hypersaline, and so is much of the groundwater.  Depending on the location, the water reservoirs can also be acidic or basic or have interesting concentrations of other ions, but almost everything moist on the planet is very salty.  The exceptions are clouds, rainwater, and areas where the soil has been washed free of salt.  The salinity does help keep the lakes and ocean at equatorial and mid-latitudes from freezing at night and during the winter.  Chott has ~30 degree obliquity with large long-term oscillations  and ~26 hour rotation, so nights can get quite cold.

Mid-morning in a dry lakebed on Chott.  The high ground on the horizon is about 20 km away.  There is still some surface water in the basin, feeding a multi-colored brew of microbes.  But that is 2 meters downhill and ~50 km behind you.  This was the first place the characters in the role-playing scenario encountered.

Basically, the nicest-to-humans areas of Chott are something like the Mojave.  Other areas are like the Atacama , with a bit more precipitation but lower temperatures.  At the poles, it gets cold enough to freeze out CO2, but there isn’t that much in the atmosphere.  As you can tell, I designed this place to be somewhere where humans could just barely survive without lots of sophisticated technology.


There is life on Chott, based on nucleic acids and proteins and using several different sources of energy.  There are sufficent oxygen-producing organisms that the atmosphere has enough oxygen for humans to breath (partial pressure ~0.2 bars), and enough consumers of CO2 that the partial pressure of that is not so high as to be toxic to humans, although there is still far more of it than on Earth.  But how did the Chott biosphere evolve?

Halophile microbes and larger organisms on Earth evolved into those environments, and almost all survive by expending lots of energy to keep their insides relatively free of salt as compared to their surroundings.  This is necessary because many normal (for life on Earth) proteins are not soluble in salt water.  Increase the salt concentration too much, and they come out of solution – salting out.  It has been far easier for Earth microbes to adapt cell membranes to keep out the high concentration of salt than it has been to use an entirely different set of proteins with a greater propensity to form hydrogen bonds with water molecules.

Life on Chott works differently.  The background of simple proteins accessible in whatever equivalent there was of primordial soup were ones that on Earth could have been too soluble for their jobs.  The structural materials used by early Chott microbes were solid/gels/membranes in salt-rich environments, but would dissolve or disintegrate in low-salinity places.

This causes an obvious problem for larger organisms outside of the oceans, lakes, and groundwater: they will dissolve in pure rainwater.  Combined with the high value of water on much of Chott’s surface, this means that the plants and animals on the land will all be armored with shells of things that don’t dissolve in pure water – be those proteins or non-polar hydrocarbons or some long-chain organic polymer.  For the plants, only areas above ground need to be armored, since water below the surface will have mixed with the soil and picked up enough salt to be usable.  At the risk of being insufficiently creative and of overselling convergent evolution, I designed a few Chott plants inspired by real succulents.

Chott plants.  The shape and surface texture were inspired by Euphorbia obsesa, but the color is different because Chott plants don’t use chlorophyll.

The need for protection against rainfall extends to the animals.  Some may be exoskeletal, others simply have thick hides.  Something like a thorny devil would work, since any means of collecting water is useful as long as that water can be combined with a little salt-rich dirt before being drunk (or as long as whatever equivalent the animal has of a stomach has a water-insoluble lining).
Both the animals and plants differ as much from place to place on Chott as on they do on Earth.  There is no such thing as a single-biome planet.  I have not detailed the entire biosphere, because that would mean generating a consistent ecosystem of hundreds of thousands of different species.  But I have considered various interesting local variations.
In areas with relatively high rainfall, the density of plants becomes high enough that there is an advantage to being taller than the plants around you.  That leads to things not entirely unlike trees.  One difference is what they use for support.  Woody plants on Earth use cellulose and lignin.  But tall Chott plants use salt crystals surrounded by organic membranes.  The areas that could be called forests are underlaid by large deposits of rock salts – both halite and salts other than NaCl.  Groundwater brings in some salt from areas uphill, and the insoluble membranes prevent the dead trunks from dissolving away too quickly.  These forests can’t grow up onto ridgelines, since there is no supply of salt there once the local soil has been depleted.

What Have I Missed?

So that is Chott, in terms of planetary science, geophysics, geology, meteorology, biochemistry, and biology.  What have I missed or gotten wrong?

Your Turn Round 1-2 will go into the history and cultures and economics of Chott.  And you all can thank Rachel for the pictures.