Mars Trilogy: The Crucible

Part of the Mars Trilogy Technical Commentary Series. Contains spoilers for this chapter and earlier chapters. Google Mars .kml. Literary commentary podcast.

The opening prolog to this section describes the formation of the planet Mars, so we have many opportunities to put our nerd hats on. One of the main reasons I am writing this commentary is to reflect on the knowledge we have gained in the ~30 years since the Mars Trilogy was written, but in reviewing this section I am reminded that despite our incredible gains, many of the mysteries raised are still mysteries and will likely remain thus until many years after humans walk there. Still, what we have is not nothing, and it is very cool.

In the text, KSR describes planet formation as “rocks banging together in space,” which is not wrong. Planetary accretion is still an area of active research with several unsolved problems. For example, it’s not completely understood how primordial dust grains, which are ~10 microns in size, first stick together. They are too small to have sufficient gravitational interactions, at least at close range, so broadly speaking there must be something happening with electrostatic forces. The problem is that electrostatic forces can be repulsive as well as attractive.

Next up, we read that Mars’ small size led to premature heat loss, core solidification, loss of differential rotation, and as a result no magnetic field. We now know this isn’t the entire story, which is super cool. First, Mars Global Surveyor (launched in 1996) mapped Mars’ magnetic field and found surprisingly strong remnant crustal magnetism, indicating that Mars almost certainly had a dynamo once.

While its magnetic field isn’t nearly strong enough to prevent gradual loss of its atmosphere due to stripping by the solar wind, it is strong enough in some places to form aurorae. Even weirder, the crustal magnetic field is striped similarly to Earth’s oceanic basalt, which was only understood in the context of plate tectonics (invented in its modern form in 1957!) and geomagnetic reversal. While we have no reason to suspect that Mars’ dynamo couldn’t have reversed before it ultimately stopped, there doesn’t seem to be evidence for the continual formation of new crust that this sort of imprinting would require, so chalk it up in the “solved one mystery, found six more” column.

Second, the way in which planets make magnetic fields is still poorly understood, and was in fact identified by Einstein as one of the big mysteries more than a century ago. I studied it during undergrad when, in ~2008 it still was not really understood, and even today we don’t get it. We have a bunch of theorems that exclude all the simple possibilities, but magnetohydrodynamics in the general case is really complicated! Still, in 1995 Glatzmeier and Roberts published a simulation of Earth’s geodynamo (or a numerically tractable approximation with much higher viscous dissipation) performing a reversal.

I haven’t read deeply on this topic since about 2013, but when I last checked there weren’t any published follow up studies (despite advances in computation) that added substantial new insights (updates welcome!). For a necessarily imprecise heuristic explanation of what is going on, the Earth’s core generates heat from nuclear decay and iron crystalization. This heat is transported through the molten iron/nickel outer core through convection. Convective efficiency is impeded by magnetic forces on the molten metal currents, both fluid and amperic. Combined with coriolis force we end up with self-intensifying, multiscale, turbulent rotating “storms” of molten metal, with a characteristic timescale of a few thousand years. These rotating cells provide the necessary geometrical characteristics to generate magnetic fields, which feed back on themselves to create yet more magnetic fields. Over time, the transported heat gets dumped into the lower mantle, which has a much longer dynamical timescale (~100 million years) and the storm currents migrate away from the equator towards the poles, just like hurricanes/cyclones, which are also heat engines but mercifully do not involve magnetic fields. Once the polar parts of the core mantle boundary (not to be confused with the other CMB) are sufficiently heat saturated, the mechanism shuts down and restarts nearer to the equator, sometimes with the opposite polarity, which causes a geomagnetic reversal. Because the pattern of Earth’s geomagnetic reversals are imprinted in rocks as they are formed, they are incredibly valuable for dating rocks. Sometimes, enough heat is dumped into the CMB to cause a large blob of hot mantle rock to migrate upwards, causing other forms of excitement, of which, more soon.

Third, relatively recently we have acquired much better information about the interior structure of Mars from the Insight mission. Sadly, this lander was declared dead the same day I write these words due to accumulation of dust on its solar panels. Using a sensitive seismometer, Insight was able to probe the interior of Mars, which became the third world (after Earth and the Moon) have its core thus measured. It turns out to be larger than expected, but containing some lighter elements.

The RISE instrument, supplied by JPL, enables tracking of the lander’s position relative to Earth to a precision of just 2 cm – better than GPS despite the distance. Careful monitoring of Mars’ rotation enables measurement of differential core rotation, which turns out to exist. So Mars still has a molten outer core, differential rotation, but no dynamo, probably because (like Earth, if magnetic fields stopped today) direct conduction is adequate to transport radiogenic heat into Mars’ mantle, and without magnetic fields to impede heat flow, there isn’t enough rotational flow to drive a dynamo.

Next, we read about the Tharsis terrane. Mars’ surface has some very odd lumps and bumps, and lacking the filtering, smoothing effect of an active water cycle, has retained scars of its formation.

The most salient feature of Mars’ topography is the dichotomy between the relatively smooth (young) low altitude surface in the northern hemisphere, and the rough, cratered (old) high altitude southern hemisphere. It doesn’t take a huge leap of the imagination to suppose that the north’s surface obscures ancient craters because it was resurfaced by some primordial ocean or two, but the ocean’s existence and character is still controversial.

The second most salient feature is probably the high altitude Tharsis region visible in brown on the map, and surmounted by four absolutely colossal volcanoes, which appear as white bumps. Why are they in a straight line? Good question! We have already met (briefly) Pavonis Mons, the central of the three and also positioned precisely on the equator, but the others are no less impressive.

In the text, KSR relays speculation that Tharsis may have been formed from ejecta from the Hellas basin (the deep blue hole on the lower right) that flew around the planet to the opposite corner. One of many more recent theories is that each of the major impacts (Hellas, Arcadia, Isidis, Chryse, Utopia) led to crustal delamination and local volcanism, but that Arcadia’s impact was sufficiently inclined (with ejecta focused to the north west) that delamination led to a continuing hinge, subduction, and three or four tiers of volcanism, of which the four contemporary large volcanos are the surviving remnants. In this sense, Tharsis is a proto-continent, and there’s some evidence that it did not originally form at the equator. But it is impossible for us to say for sure, and even with Mars-based labs doing nothing but radioisotope dating and paleomagnetic field studies, we may not ever know the answer with certainty.

Next, we read about the late heavy bombardment, a period relatively late during planetary formation during which the inner solar system was hit with a much higher rate of impacts on already-formed planetary surfaces, resulting in essentially all the lunar cratering we can observe from Earth, the perfect sterilization of the surface of the Earth, and the craters visible on the southern hemisphere of Mars. Also, it’s possible that the LHB never actually occurred. As much of Mars preserves its ancient surface and its crust has not been regenerated, it seems safe to assume that, at least in the southern hemisphere, the crust is composed of kms-thick layers of packed rubble, which is quite different from the Earth’s mixture of granitic intrusions and neatly ordered sedimentary beds.

Regardless of whether the LHB actually occurred, the planetary surfaces tell us that there was a time when lots of big rocks fell from the sky, and then that time gradually came to an end. Before it did, though, Mars took some absolutely monster hits. It is possible that some of these were other bodies that formed on Mars’ orbit, as Earth’s Moon-forming impactor is thought to have done. Some simulations have the solar system forming dozens or hundreds of planets before orbital resonances cause them to impact each other, fall into the sun, or be ejected from the solar system altogether. Mars’ gravity was too low, its geological processes too slow, and water cycle too dry to undo this damage, and so we can see it even today on the topographic map. At least five or six craters big enough to blast out holes kms deep and 100s of kms wide, plus innumerable smaller ones. Enough rock was blasted off each of the rocky inner planets that decent quantities found their way to all the other planets! We still observe some meteorite falls here on Earth that appear to be rocks dating to the LHB.

KSR speculates that Mars’ small moons Phobos and Diemos were also formed from impact ejecta, as we now understand the Earth’s Moon was. Current thinking has not ruled this out but it seems more likely that they are captured asteroids, but not without mysteries. Both have crater chains on their surface apparently from ejecta sprays emitted from Mars’ surface. And Phobos orbits so low it appears to go backwards across the sky and is relatively close to the Roche limit, raising the possibility that Mars might have once had more moons and have eaten some already.

Speaking of craters, KSR describes crater saturation, wherein the surface is completely covered in overlapping craters and any new impact erases as much as it creates. The surface of the Moon is also in this state, effectively for any crater smaller than about 100 m it is safe to assume multiple craters of that size scale have existed in that location. For more info, see the discussion around page 83 of the Lunar Sourcebook.

We get a brief discussion of the early water cycle, which left channels from cataclysmic floods, followed by a period of gradual desiccation as the planet got colder and water froze out at the poles and on the highest peaks. More recent evidence suggests that Mars can still experience short (~100,000 years) intermittent warmer/wetter periods, perhaps triggered by large asteroid impacts, but that the climate reliably reverts back to cold and dry, which is the state we find it in. One incompletely solved mystery is that when Mars was warm and wet, 4 billion years ago, the sun was significantly dimmer than it is today, due to the then lack of fusion products in its atmosphere. How could Mars have been warm enough? Most probably, the greenhouse effect was stronger due to greater volcanic outgassing, and absorption gaps were closed by “collision induced absorption,” preventing heat escape.

We also get some speculation about where water might be today, both in buried ice caps, buried frozen lakes and seas, and gradual refilling of deep-crust aquifers from the mantle gradually outgassing water in the 3-4 billion years since they last broke out. Below is a screenshot of the Dao Vallis outflow channel and valley head in the north-east part of the Hellas basin. Billions of years ago, the water-saturated aquifer here on the north east slope of Hellas Planitia appears to have collapsed, liquified, and flowed downhill. I say appears, because intervening erosion changes the character of channels and valleys, removing smaller features and widening larger ones, so these features were almost certainly part of other, more developed drainage systems that are now mostly invisible.

We also now know that subsurface ice is fairly common on Mars, particularly at the higher latitudes. It has been directly imaged in craters, under landers, and on cliff walls. It was a fair guess in 1992 that Mars would have a lot more water than had been directly detected by relatively primitive missions at that time, but the specifics, as always, turned out to be much weirder than we expect!

One area of active controversy is just how much outgassing we should expect from the Martian mantle. In particular, CO2 evolution that occurred on Earth and Venus is driven by pressure-induced calcination of carbonate rocks at depth, and Mars’ gravity isn’t high enough to efficiently drive this process. Therefore, it is possible that, in addition to stripping by the solar wind, Mars doesn’t have much of an atmosphere today because its volcanoes have emitted much less CO2 than Earth’s.

KSR mentions inclination variations of 51,000 years. In addition to this ice age cycle, which is similar to the Earth’s, the location of Mars’ pole relative to its crust has also likely varied over geological time due to true polar wander. Depending on how relative mass distributions shift within the solid but ductile mantle, the location and relative magnitude of the principle axes of the planet’s moment of inertia can shift. This causes the mantle to gradually slide over the core, shifting the location of the axis and equator relative to surface landmarks, which are coupled to the mantle on Mars, which lacks tectonic drift. TPW has also occurred on the Earth, but on Mars the most salient example is that the formation of Tharsis permanently unbalanced the planet, with the result that this positive mass anomaly shifted onto the equator, and the resulting stresses from translating the planet’s hydrostatic bulge may have contributed to the formation of the Valles Marineris.

As the planet cooled, “ceaseless winds carved the land, with dust that grew finer and finer.” We have pretty good Mars analogs in Death Valley, where the wind has carved rocks into impossible faceted shapes, but humans still lack intuition for understanding the Mars’ surface. It is so old! In the absence of water or subduction, rovers have discovered pebbles laid down in streams billions (!) of years ago. That said, even Mars’ thin atmosphere and relatively light winds can move a lot of dirt, given enough time.

This image from Curiosity shows layers of lake sediments visible on the slopes of Mt Sharp. How were they formed? It seems likely that the lake in this crater formed long enough to bury it in hundreds of meters of sediment. Since the climate dried out, wind has eroded many many cubic km of rocks, re-exposing this glorious stratigraphy. At the same time, wind currents deposited sand and grit in the center of the crater, eventually building a mountain 5.5 km high!

The last salient piece of exposition in the chapter prologue is an apparently authorial voice telling us that life never formed on Mars. Even 30 years later we still do not know if life formed there, but the current science program (led presently by the Perseverance rover) is oriented towards answering this question. There is, though, some strong circumstantial evidence that life did indeed form on Mars, and it’s even possible that Earth life was seeded from Mars, which had liquid water and suitable surface chemistry more than 100 million years before Earth did. In my view, the most compelling evidence for life on Mars is the presence of apparently biogenic magnetite crystals in ALH84001, a meteorite from Mars. Hundreds of these crystals, with size, shape, isotopic disequilibria, and other characteristics unique to Earth life, have been found in this meteorite. It is not impossible that they could have been formed some other way, but AFAIK no crystals of this type have ever been successfully synthesized in the lab, while magnetotactic bacteria churn them out on a routine basis. I personally think it is likely we will find microbial life on Mars, and I have even bet money that when we do, it will be a superset of Earth biochemistry.

We have successfully turned a two page prologue into 2600 words of discussion, and there are only about 115 pages left in this chapter. Strap in!

Part three provides Nadia’s perspective as she builds Underhill, the first (nearly) self-sufficient outpost on Mars. Through the course of the chapter, Nadia’s journey gives us insights into logistics, organization, and two traverse tours through spectacular Martian geography. Much of the material for this chapter was derived from “Case for Mars” conference books, which I don’t have handy, but which form the technical underpinning for the story.

First, we share the impression of walking around on Mars. Nadia sees the landscape dotted with landers, sent out in advance and loaded with cargo the First Hundred has to collate and assemble into their base. The landers are described as “stick legged,” anticipating the side-landing configuration of the Mars DRA triconic lander, essentially a cylinder landed on its side with a cluster of rockets on either end.

Nadia remarks that Mars, being a smaller planet, has closer horizons than Earth. On Earth, the distance to the horizon if standing on the beach is about 4.8 km. On Mars, it’s just 3.4 km, with just half the visible area.

At first the First Hundred live in a “trailer park,” within a set of hab landers. They are described as having four toilets, sleeping births on the floor (working during daylight hours only), and an airlock big enough for three. They also have gender segregated changing rooms! More than once, differential thermal expansion caused by Mars’ intense cold causes doors or fittings to jam. Coefficient of thermal expansion (CTE) is a major design constraint in all kinds of real-world machines involving moving parts, particularly if those parts are made of different metals with different CTEs. Old-fashioned toasters used a bimetallic strip that moved a lot with temperature to trip the latch once they got hot enough.

At Underhill, water is mined from the atmosphere. The air miners, built by Boeing, fit within the standard lander form factor – a cylinder roughly 30 m long and 5 m wide, mounted horizontally, with compressors at either end to ingest the thin Martian atmosphere, separate the components, liquefy, and store them. It is not specified how they are powered. The Perseverance rover has an air mining experiment (MOXIE), which compresses CO2 and separates it into CO and O2, as a pathfinder for later systems such as the air miners described in the novel. Mars’ atmospheric pressure is too low to force through a HEPA filter, so Mars air compressors must have a dust-tolerant first stage. MOXIE used a scroll pump.

Later on, Nadia hauls an apparently fully loaded air miner from the landing zone to the factory zone in the eastern part of the base. It contains 5000 L of ice, 3000 L of liquid oxygen, 3000 L of nitrogen, 500 L of argon, and 400 L of CO2, for a total weight of about 12.5 T and volume of about 12 cubic meters – a relatively small fraction of the devices’ overall volume.

We get a brief description of the walkers, previously described as likely mechanical counter-pressure suits. They are formed of some kind of elastic mesh, like a thin stiff wet suit that allows for freedom of movement while still being difficult to put on. Mechanical counter pressure suits tested in the 60s were composed of multiple layers and took hours of strenuous effort to put on! As their primary function is to impose mechanical pressure on skin (normal skin lacks enough collagen to hold together in Mars’ almost vacuum atmosphere), they are much more robust to damage and tears than a gas pressure suit, but depressurization of more than a few mm of skin results in bruising and, eventually, freezing. Freezing is likely to occur only if the exposed skin touches a solid that can conduct away its heat as thermal radiation and convection on Mars are inadequate to cool off small exposed patches faster than blood and the body’s thermal conduction can keep it warm.

The walkers are not airtight and dust gets in – micron sized fines similar in scale to particulates that make up air pollution in major cities (PM 2.5). Like air pollution, the fines make their way into lungs, blood, and the astronauts’ brains. Gradually they are blurring into the landscape.

The walkers have a metal neck ring to interface with a gas pressure helmet, so they must have some kind of sealing collar to enable a transition from mechanical pressure over most of the body to gas pressure over the head. In the real world, there are a few different approaches to this problem, as mechanical systems struggle to apply even pressure over parts of the body with mobile concavities, such as hands and feet, as well as parts of the face that prefer to interface with air. Variations include gas pressure gloves and boots, full head helmets, face masks, and even balaclava-like systems that draw from SCUBA masks and regulators. This is an unsolved problem! If you have the time and interest, you could solve it!

Walkers have, or at least can support, a “wristpad” as a computer interface. While other computer systems are described in more familiar terms – keyboards, CRT monitors (zoomers, look it up!), the wristpad is a touch screen not unlike a small iPad, introduced in 2010. Today, we would identify it with a bulky smart watch.

On landing, the prevailing wind is from the south, consistent with katabatic winds at that location. The location of Underhill is given as 100 km NW of Ganges Catena and 130 km NE of Hebes Chasma (differing from the map in Red Mars). In CTX imagery, EW dunes are visible, lending credence to this guess. The wind on Mars is fast but the air density is low so under ordinary circumstances people can’t feel the wind, but can see its effects on extremely fine dust (fines, ~2.5 microns in size) shooting past in a sinuous flow.

Nadia and her crew’s major job is to unload landing vehicles and disposition their contents. We get a glimpse of this process as she unloads a huge, bright blue Mercedes-Benz tractor, apparently packed within a crate that she opens using a drill and Phillips head bit. I’m inclined to think this is to characterize Nadia as brutally pragmatic, as 1) why would precious mass be wasted with a crate as intermediate packaging 2) why would the crate be secured with a threaded fastener as opposed to some kind of clip 3) why would the threaded fastener use a Phillips tool and 4) why would Nadia use a drill rather than an impact driver to undo it?

The tractor, once unpacked, is driven down an improvized ramp made from the remains of its crate under remote control. Its wire mesh wheels (more robust than rubber at extreme temperatures) are driven by a 600 hp hydrazine engine. Hydrazine (N2H4) is to ammonia as ethane is to methane, only quite toxic to humans, liquid at higher temperatures, and a capable monopropellant, dissociating into N2 and H2 with an iridium catalyst. It is a propellant of choice for many satellites though the hunt is on for a less toxic replacement. Straight hydrazine has a melting point of 2C, so operational realities on Earth and on Mars will compel the use of related variants such as MMH, UDMH, or their 40-60 mixture, which is liquid down to -80C.

The hydrazine engine (likely a turbine) drives a hydraulic powerpack, and the rest of the tractor operators as it would on Earth, with pressurized hydraulic fluid being shunted through valves to activate pistons and hydraulic motors. Because hydraulic systems are sealed and operate at high pressure, they can operate in vacuum with minor modifications and, of course, an air-independent prime mover.

Part of the fun for Nadia is driving around in the tractor inspecting landers to discover what’s in them. This implies that, back in the wilds of 1992, there was no precise inventory tracking, TRN pinpoint landing, Mars global positioning systems, RFID remote cargo discovery, etc. Nadia and her colleagues have to physically climb onto each lander, rub dust away from the manifest, and copy it down! Of course, back in 1992 we had only Viking data, with roughly 300 m resolution. After Mars Global Surveyor, landers found much smoother landing sites and constant improvement of landing precision shrunk targeting from 100 km down to just 4 km!

For context, I have a mostly complete spreadsheet of Mars global imagery datasets. Everything after row 11 occurred after Red Mars was written. Fortunately the Underhill site is almost completely flat, and while at higher elevation than NASA prefers to land under parachute, is not impossibly elevated.

As part of this treasure hunt, the team locates a shipment of solar panels, then a packaged nuclear reactor. Despite Arkady and Phyllis arguing over the reactor, Underhill surviving on Mars runs an impossible gauntlet of material scarcity, labor scarcity, and energy scarcity. Without effectively unlimited free electricity, survival is not possible. The base needs a big reactor. As described, it’s a Rickover adapted from the US Navy, a design safe enough to share the interior of a pressure hull with hundreds of submariners for decades with no major safety lapses, but Arkady calls it “Chernobyl” out of spite. Its power is given as just 300 kW, which would be one of the smallest nuclear reactors ever built. For comparison, an aircraft carrier reactor can deliver about 400 MW (1300x as much) without breaking a sweat.

We get a list of tools that Nadia collects for her personal set. It seems reasonable, if a bit light on hammers.

Allen wrench set, some pliers, a power drill, several clamps, some hacksaws, an impact-wrench set, a brace of cold-tolerant bungie cords, assorted files and rasps and planes, a crescent-wrench set, a crimper, five hammers, some hemostats, three hydraulic jacks, a bellows, several sets of screwdrivers, drills and bits, a portable compressed gas cylinder, a box of plastic explosives and shape charges, a tape measure, a giant Swiss Army knife, tin snips, tongs, tweezers, three vises, a wire stripper, X-acto knives, a pick, a bunch of mallets, a nut driver set, hose clamps, a set of end mills, a set of jeweler’s screwdrivers, a magnifying glass, all kinds of tape, a plumber’s bob and ream, a sewing kit, scissors, sieves, a lathe, levels of all sizes, long-nosed pliers, vise-grip pliers, a tap-and-die set, three shovels, a compressor, a generator, a welding-and-cutting set, a wheelbarrow…

Despite planners budgeting 10 days, it took a month to open all the freight, check the contents, and move it to stockpiles, which might be a reference to logistical hurdles on Skylab 4. Assuming a team of 60 people are working in pairs to unload 2 landers per day, this implies 1800 landers, each with 20-30 T of cargo, for a total of 45000 T of cargo, or 450 T per capita. This seems like a lot, but the per capita cargo mass allocation must start quite high with a bunch of materials that will soon be manufactured on Mars, and over time will drop down to essentially just a person, their personal effects, and whatever they need to keep them alive on the journey from Earth.

At this point the entire town is knolled, awaiting assembly. Hiroko naturally prioritizes the farm, which becomes 3 small greenhouses with thick walls and seals. They have five years of food, even burning 6000 calories per day, which is about 280 T of food in total. The farm requires manufacturing soil, which is accurately characterized as salty, explosive with peroxides (and perchlorates!), arid, and having no biomass. Healthy soil on Earth has signficant stores of reduced carbon, bacteria, and fungus, all of which have to be grown from scratch on Mars. Then, fertilizers which enrich the soil’s supply of nitrogen, phosphorus, and potassium. Nadia assists Hiroko with “Hermetic seals, lock mechanisms, thermal engineering, glass polarization, farm/human interfaces.”

Sax Russell and team set up the factories. Vlad and Ursula get cracking on the biomed labs. Ann works twice as hard as everyone, running full time on construction and full time on geological surveys. She eschews work on the factories or farm, living her belief that Mars should not be made hospitable to humans.

Meanwhile Arkady and team are up on Phobos, suffering for a lack of gravity. Nadia suggests building a train around the perimeter of the small moon, providing centrifugal gravity outwards. Of course, it is slightly more practical and much less fun to just build a large rotating room somewhere deep inside the station as a conventional centrifuge. KSR describes a similar set up in “Red Moon.”

Nadia begins to build the permanent habitat, which for some reason is embedded in a deep, labor intensive trench 10 m wide, 50 m long, and 4 m deep. Having dug this enormous hole through rocks, clay, and dust, Nadia backfills it with a 2 m thick Portland cement foundation. If the cement is made on Mars, they must have some local source of carbonate rock. On earth, this is usually limestone from the remains of ancient reefs, but the Underhill location is far from the Mars paleo-ocean and, regardless, Mars is lifeless in KSR’s universe – the aliens are from Earth.

The permanent habitat consists of nylon-parachute-reinforced bricks, assembled mostly robotically into barrel vaults, with six chambers per side. Robotic installation suffers the usual “garbage in, garbage out” problems that characterize inadequately robust software systems interacting with the real world, and which human bricklayers can handle with ease – if Nadia had a reliable supply of unlimited labor, which she does not! These vaults are covered with 10 meters of regolith to provide adequate counterpressure, preloading the arch against 450 mBar pressurization. Given that it will be covered with so much rock and sand, it’s unclear why it has to be debossed into the subsurface at all.

The interior is sealed with a plastic liner, the structure is festooned with metal lock doors, kitchens, climate control, electrics, plumbing, and bamboo interior structure, almost all of which must be installed by hand. Fluorescent lights are employed, presumably to offset the excessively wholesome, earthy ambiance, and lack of natural light. Heating elements are embedded in the wall, which hides them but makes servicing impossible. The completed structure is reminiscent of vaulted ruins at Aptera in Crete.

They were like Cro-Magnons in a cave, living a life that was certain to be pored over by the archaeologists of subsequent generations; people like her who would wonder, and wonder, and never quite understand.

Later, she has to blast holes in the improbably thick concrete foundation to build cellars, and lower the level of a greenhouse to let light into windows added to the inner wall of a quadrangle, which has an established greenhouse inside. In other words, there seem to be some build sequencing issues here! It’s always easier to move vacuum tolerant materials in and out of the hab before it’s sealed and pressurized, just as it’s easier to leave gaps in concrete for future access, pipes, etc than make them after.

Nadia describes the soil as having less than 0.1% water content, though of course clay is a hydrated mineral. We know now that there’s a lot of water on Mars under the surface, including in Underhill’s area, with numerous glaciers above roughly 40° of latitude. KSR could have reasonably guessed this but, like most of the more stretched science, there is a narrative reason why Underhill is dry and NASA decided to set up a base in a dry location.

Nadia helps Sax unclog a Sabatier reactor, a catalytic chemical process that converts H2 and CO2 to CH4, or methane. Methane, the primary component of natural gas, is an important fuel and chemical precursor. The Sabatier reaction will underpin mass adoption of solar powered synthetic fuels here on Earth.

Sax points out that machinery from automotive makers is low powered and reliable, while machinery built by aerospace companies is outrageously high-powered but breaks down twice a day. Partnership products have terrible design, demonstrating Conway’s Law, which states that “Any organization that designs a system (defined broadly) will produce a design whose structure is a copy of the organization’s communication structure.” Chemical equipment is finicky – truer words were never spoken. I have written blogs on Building the Mars Industrial Coalition and New Opportunities for Space Companies, describing how existing industrial companies can leverage branding and talent acquisition by contributing their expertise to efforts to put people on the Moon and Mars.

We get a list of chemical processes being activated in the alchemists quarter.

The Boeing air miners had been only the start of the factory complex; their gases were fed into big boxy trailers to be compressed and expanded and rendered and recombined, using chemical-engineering operations such as dehumidification, liquefaction, fractional distillation, electrolysis, electrosynthesis, the Sabatier process [CO2 + 4 H2 -> CH4 + 2 H2O], the Raschig process [hydrazine], the Oswald [sic] process [nitric acid]….Slowly they worked up more and more complex chemicals, which flowed from one factory to the next, through a warren of structures that looked like mobile homes caught in a web of color-coded tanks and pipes and tubes and cables.

In addition to this list, mines are set up to extract magnesium (a structural metal even lighter than aluminium) that is attracting renewed interest. The plants described are typically enormous and labor intensive, so we have to suspend disbelief that a team of 10-20 scientists can assemble and commission this capability, on Mars, in just a few months. On Earth, they would typically be multi-billion dollar projects. The hostility of the environment is underscored by (too real) descriptions of endless pumps, mechanical failures, and dust contamination.

Over the first year in Underhill, their automated factories produce:

sulphuric acid, sorel cements for the vault mortar, ammonium nitrate explosives, a calcium cyanamide rover fuel, polysulfide rubber, silicon-based hyperacids, emulsifying agents, a selection of test tubes holding trace elements extracted from the salts, and, most recently, clear glass…

Meanwhile, the bio team has already begun to engineer microbes to survive in the subsurface, as part of their ideological commitment to bring life to Mars. This process, conducted in (mostly) sealed Mars surface analogs including one of the trailer habs, can only be described as gain-of-function research, which lands a bit different in 2023 after it’s implicated involvement in the origins of the COVID-19 pandemic. In the end, the First Hundred need UN permission to begin an open air garden, which conveniently arrives at the end of the chapter.

Then follows an exquisite two page sketch of work in progress on the base. The base is cluttered, and tracked, given over to industrial production. It stretches in all directions beyond the horizon. Alchemist’s quarter and Chernobyl is to the east, the permanent hab to the north, storage area and farm to west, biomed center to the south. In this sense, it echoes the layout of the Amundson-Scott south pole station, which has sectors allocated for different scientific purposes.

Lacking communications satellites, Nadia can only talk by radio with Arkady when Phobos is visible in the sky, and they swap recommendations on good soundtracks for a day’s work. KSR calls out Louis Armstrong in 1947. Nadia calls it their second spring of life, but remarks that Hiroko, for all her systems genius, can’t hammer a nail straight. Hiroko and the farm crew have already gone native, performing a chanting ceremony during the midnight time slip.

With the first vault complete and three more to complete a square under construction, the base has pressurized volume to spare, and the next salient growth constraint is the availability of water. The farmers are starting a swamp in biosphere. Nadia wants swimming complex with lap pool (with extra splashy water in the low g), whirlpool baths (i.e. a jacuzzi), and sauna, to gratify their “aquatic dolphin brains.” A reference to Soviet ergonomic theory perhaps? Underhill has no local water supply, limited air miner capacity, and so relies on giant trucks to digest surface soil and separate out what little water is there. As they’re built by a French-Hungarian-Chinese consortium, Underhill leadership fears they could wear out and leave the base parched.

Meanwhile, Arkady sent down videos of their artistic station on Phobos, which was fractured by the Stickney impact and full of water ice veins – convenient for the plot but less likely in such a small, dark body so close to the sun. Phobos is described as a chondrite, one of three different kinds of asteroids. Ann and Phyllis argue about using Phobos’ ice to supply Underhill with water, by sending it down in landing vehicles (LVs). While Phyllis was on the right track regarding activating their nuclear reactor, her advocacy of bringing water in by rocket is so far off the mark I really have to wonder. The rocket fuel required to fly the LVs back to Phobos is made, in large part, from water, and a round trip would require about 10x the water in fuel than it could possibly deliver. Ann’s objections center on the waste of energy required to do this, which is also true (local water is cheap water) but not nearly as salient, particularly if, thanks to the nuclear reactor, energy is nearly infinite anyway.

Meanwhile, Ann invites Nadia on an expedition to Hebes Chasma, a 320 km-long pit in the ground just 130 km to the south west of Underhill. KSR describes the far wall of the pit being visible which is possible given the great vertical relief and relatively sparse atmosphere.

Ann proposes floating a pressure-stabilized dome over the entirety of Hebes Chasma, terraforming within, and leaving the rest of the planet untouched. In this, it is apparent, she has few allies.

Vlad is concerned about the radiation impact. Now that the permanent hab is constructed, he advocates cowering within, depending on teleoperation of machinery, limiting exposure to 10 rems (100 mSv) per year, and adding additional radiation shielding. The pro-terraforming faction advocate thickening the atmosphere to block radiation, but concede it’s unlikely to occur fast enough for their own exposure. As discussed in the commentary on the previous chapter, we now know unshielded humans on Mars will take about 250 mSv per year, which is about as spicy as radiation exposure can get with very limited evidence of any long term harm. Of course, people on Mars are shielded when they’re inside sleeping or working, so exposure will be well below this level anyway. Vlad says people should only go outside at dawn or dusk, which doesn’t make much sense as far as radiation exposure goes – cosmic rays are isotropic and solar radiation is mostly blocked by the atmosphere.

We get a nice discussion of dates and seasons on Mars, which are measured by angle around the sun in degrees. Mars has a rather eccentric orbit, meaning that Mars’ hemispheres have different seasonal patterns. That is, in the northern hemisphere, the extremes of summer and winter are partially canceled by Mars’ relative distance from the sun while in the south, the differences compound. Additionally, the south is generally at higher altitude, and thus having longer colder winters has a larger polar cap. KSR relates received wisdom c. 1992 that the southern polar cap is mostly CO2 (dry ice), while we now understand that both caps are mostly water ice – though the southern one is considerably larger. This is not always true. Due to orbital precession and gravitational interactions with Jupiter, the phase between Mars’ argument of perihelion and its inclination vary over timescales O(100,000 years), meaning the relative magnitude of its poles have switched tens of thousands of times in geological history.

With the base nearly complete, Nadia’s story line requires that she take the readers on the first of many long, traversing tours of the surface of the planet. The first is a rover trip to the north pole, ostensibly to secure a supply of water. But first, she needs to survive a life-changing injury.

Against the backdrop of Nadia’s unwilling participation in the Maya/Frank/John drama, caused perhaps by their ability to have private radio bands but no individual text messages/WhatsApp groups, Nadia is called to assist with a mechanical breakdown. A Sandvik Tubex boring machine installing a (inexplicably subsurface) water line to the permanent habitat has suffered frozen hydraulic fluid, and an Allied (defunct 1985) hydraulic impact hammer has gotten stuck in a boulder. While freeing the bit, the pressurized (live, not safe!) machine suddenly retracts, crushing Nadia’s hand. This is just one in a long line of harrowing injuries hydraulic systems can inflict on the unwary.

Nadia staunches the bleeding by “icing” her torn walker glove and stump against the deep-frozen ground, then gets patched up. While she recovers, she spends time in her baths complex, enabling us readers to see the toll that heavy labor has taken on the First Hundred during the construction of Underhill. Following a power law distribution, most of the injuries are relatively minor, typically frost burn in the form of black skin that eventually peels, along with a few other broken bones and, so far, no deaths. It is interesting that in KSR’s work, we get a visceral appreciation for their work through its physical impact on our characters. For a real Mars base, of course, the labor shortage is so acute that human muscle is unlikely to be anywhere near the critical path.

After a short period of enforced idleness, Nadia allows herself to accompany Ann, Simon (descriptive geologists), Phyllis, George, and Edvard (prospecting geologists who also have an undercurrent of young-Earth creationism?) on an epic traverse north towards the polar cap to set up a water distillery. Their vehicles for exploration are three big long range rovers. Each has two, four wheeled modules coupled by a flexible frame. Built by Mercedes Benz, they are sea green in color. The forward modules contain living quarters and have tinted windows on all four sides, while the aft modules contain the fuel tanks and a few solar panels. The wheels are wire mesh (like the tractor earlier) and 2.5 m high, and enable the rover to cruise at 30 km/hr. I envision them as slightly larger Sherps.

The route from Underhill to the pole and back is nearly 12,000 km. Hydrazine under catalytic decomposition has an energy density of 1.6 MJ/kg, while combustion with N2O4 (2N2H4 + N2O4 -> 3 N2 + 4 H2O) has an energy density of about 11 MJ/kg including the oxidizer. Gasoline burning ambient oxygen on Earth has an energy density of 46 MJ/kg, which is much higher. For a car that gets 50 MPG, a 12,000 kg range is achievable (at low speed on a smooth level road) with a 150 gallon fuel tank, weighing 450 kg, or a total fuel mass fraction of ~25%. Running hydrazine/N2O4 instead would require 1800 kg of fuel against a dry weight of about 1400 kg, which obviously affects performance. On Mars, it might be *just* possible to get this sort of range provided the rover is almost entirely fuel by weight when it starts out. The solar panels listed could not be large enough to provide enough energy to move the vehicle as described. Assuming the rovers use the same 600 hp power plant that the tractor does, driving at a steady pace at 1/3 throttle would consume roughly 150 kW of power, which on Mars would require a solar array of nearly 800 m^2.

The logistics of the trip are also challenged by their side mission of dropping transponders for automated ice trucks every few km and grading a road. Did they bring 2000 transponders? How are they powered? How smooth is the surface? Is the hard part of automating ice trucks routing on a scale of multiple kilometers?

On the outbound trip they begin to the northeast to avoid Tempe and Mareotis canyons, which are actually far to the north on Tharsis, on the other side of Echus. Perhaps Underhill’s location was originally close to the pole?

Once down off the equatorial divide, the landscape is described as being bumpy, with small rocks. This is consistent with imagery from Viking 1, which their route takes them very close to.

Almost all these little rocks are ground scatter from relatively recent impacts, piled on top of other rocks from impacts many kilometers deep dating back to the Late Heavy Bombardment. Below this the crust transitions from brittle to ductile, but of course the entire planet accreted from various rock piles back in the beginning. Nadia remarks that all the craters are round because they’re formed by the crust exploding after a plummeting space rock embeds itself deep within, dissipating all its kinetic energy there. This is mostly true, but if a meteor impacts at a sufficiently glancing angle, it can create a distorted crater. In fact, there’s a pretty nice one just 52 km south west of the Underhill site, and Orcus Patera is thought to be a particularly large oblique impact crater.

Their route also takes them past various fossae, or ditch-like features visible at a variety of scales on the surface, likely related to faulting.

Phyllis and Ann dispute the length of time Mars was wet in the past, with Phyllis backing a long wet past in which much of their route would have been beneath a liquid ocean. Ann backs the short wet past theory, which is still fashionable among some Mars scientists. As mentioned in the intro, the central problem is that while we can adequately estimate how much water has flowed through various channels from the quantity of rock eroded, we still don’t know how Mars was once warm enough for lots of liquid water, and we don’t know exactly how episodic those ancient flows must have been. Also, even a short wet past could still have been wet for hundreds of millions of years, which seems like a long time to me.

As the traverse takes them north, the narrative presents opportunities to show off new geography, such as the presence of thermokarsts around latitude 54, described as steep-sided oval pits 100x bigger than Earth, up to 3 km wide and 60 m deep. Spotted on Viking imagery with its 300 m resolution, we now have imaged a variety of smaller ice-related features at extreme latitudes on Mars. These may have been caused by gradual sublimation of sub-surface ice.

The group also stops for an entire day so Nadia can set up an improbably labor-intensive permafrost water collector entrenched in frozen clay – a hydrated mineral. By labor intensive, I mean that the First Hundred only has about O(10,000) human-days of labor availability to set up a self-sufficient base. By comparison, at the height of WW2 mass production, it took about 60,000 human-days of labor to build a Liberty ship, a relatively simple, small, and optimized freighter. And on this day, Nadia spends six person-days of labor to move some dirt around to produce a laughably small potential volume of water. People in the US consume about 120 T of water per year on a per capita basis. To keep procurement cost sensible, a Mars water production system should produce at least 20 T of water per person-day of labor.

Their drive continues north to Vastitas Borealis (literally: Northern Wastes) between 60 and 70 degrees north. At 70°, Phobos is no longer visible above the horizon but fortunately areosynchronous communication satellites have been emplaced to enable communication over the entire planet, although even the areosynchronous orbit is not visible above about 85°, unless there are multiple satellites in figure 8 orbits.

At this point, the writing and experience seems to take on a surreal, almost hallucinatory character. Nadia and friends are weeks away from Underhill, alone on the top of an alien world seeing things no human visual cortex has ever seen. They come across an ocean of blackish sand dunes, a band 800 km wide, tinged with purple and rose. The dunes trend north-south, and they drive on the humpbacked western (upwind) side to avoid softer sand. The dunes got steadily larger, at the typical 100x Earth size.

I will make two comments on Mars dunes.

First, because of some physics peculiarities associated with particulates and lower gravity, Mars dunes actually occur on three different characteristic size scales, as opposed to the Terran norm of two. This could be useful information if you have a tendency to wake up on Mars but find yourself unsure of which planet you are on.

Second, there are six different forms that dunes come in, depending on wind characteristics and sand availability. Mars’ dunes in Vastitas Borealis are described as Barchan in the text.


KSR describes the dune material as dark solid mineral particles. Volcanic. Not fines and salts. Earth’s sand is mostly quartz but Mars doesn’t have much granite. So the particles are the harder minerals: obsidian, flint, garnet. Beautiful black grit, not unlike the beaches of Namibia, which have been passive continental margin for 100 million years, long enough to erode away the softer minerals. I am not aware of recent scholarship on the composition of the Vastitas dune field, but orbital mineral identification is rather non-trivial, in particular because micron-thick coatings of dust can seriously disrupt spectral signatures. This was one of the reasons for the surprising result where Curiosity found a bunch of gray (not red) rocks with reduced chemistry in Gale crater.

These grains are probably volcanic silicates. Obsidian, flint, some garnet. Beautiful, isn’t it?”
She held out a handful of sand for Nadia’s inspection. Perfectly serious of course. Nadia peered through her faceplate at the black grit. “Beautiful,” she said.
They stood and watched the sun set. Their shadows went right out to the eastern horizon. The sky was a dark red, murky and opaque, only slightly lighter in the west over the sun. The clouds Ann had mentioned were bright yellow streaks, very high in the sky. Something in the sand caught at the light, and the dunes were distinctly purplish. The sun was a little gold button, and above it shone two evening stars: Venus, and the Earth.

“They’ve been getting closer every night lately,” Ann said softly. “The conjunction should be really brilliant.”
The sun touched the horizon, and the dune crests faded to shadow. The little button sun sank under the black line to the west. Now the sky was a maroon dome, the high clouds the pink of moss campion. Stars were popping out everywhere, and the maroon sky shifted to a vivid dark violet, an electric color that was picked up by the dune crests, so that it seemed crescents of liquid twilight lay across the black plain. Suddenly Nadia felt a breeze swirl through her nervous system, running up her spine and out into her skin; her cheeks tingled, and she could feel her spinal cord thrum. Beauty could make you shiver! It was a shock to feel such a physical response to beauty, a thrill like some kind of sex.

What is a road trip without a mechanical failure and opportunity for Nadia to use tools and the rock doctors to go look at rocks? Rover 2 indicates an error with a red light on the control panel, which I think is neat hauntology for an alternative universe where humans got to Mars before touch screens ate the world.

It turns out that part of the articulating connection between the two halves of the rover had sheared, which underscores first that when it comes to trucks and trailers, there is no need to re-invent the wheel, just use a semi-trailer coupling. Second, the environment is really harsh. Even at 30 km/h, the forces are high enough to rip things off the rover. It’s not specified in the text, but I like to imagine that perchlorate fines and extreme cold led to stress corrosion cracking in the 7000 series aerospace grade aluminium alloys used on this kind of machine.

It’s Ls 84 and near the summer solstice, so the sun barely sets, mostly traveling in a long slow arc close to the horizon, as it does in Earth’s polar regions. Unlike Earth, though, Mars’ atmosphere isn’t thick enough to cause substantial refraction so the sun isn’t flattened near the horizon.

It’s not mentioned in the text but it turns out that on Mars, the sky is pinkish during the day and blue at sunrise and sunset. As opposed to Earth, where the sky is blue during the day and red at sunrise and sunset. Why is this so? Rayleigh scattering, obviously. Why does it have the opposite effect in the two atmospheres? Something something Mars atmosphere has a lot of dust that is just a bit larger than a wavelength of light, while Earth’s atmospheric color is determined by scattering off air molecules. The effect can be simulated by diluting a teaspoon of milk (a colloidal suspension of tiny fat droplets) in a glass full of water. Actually color grading of Mars images from Viking was super contraversial for decades, until Pathfinder cleared it up.

Blue sunsets may have physiological impacts on Earth-evolved animals. Creatures with eyes, including some single-celled animals, are able to sense ambient color and use red light to reset their circadian rhythms and sometimes also their internal magnetic sense. Yes, many animals are able to sense magnetic fields and yes, red light can deactivate the sense. So can HF radio signals. Why? Who knows? We’re not even quite sure how animals sense magnetic fields in the first place, though there’s a good chance it’s with tiny crystals of magnetite, not-really-coincidentally quite similar to the magnetite crystals we found in ALH84001.

One hypothesis suggests that pre-Cambrian (Ediacaran) soft bodied sea creatures migrated over long distances like whales do today, that they used magnetoreception to help them navigate, and that red light at dawn and dusk deactivated magnetic sense so it could be recalibrated relative to the east/west axis of the sun’s motion. Polynesian navigators used a star compass with what we call west at the top, though there is not yet any evidence they used magnetic sense, even though some humans have it. As the animals traversed the world’s oceans, the orientation of magnetic north with true north varies due to magnetic declination, so it’s useful to reset it twice a day. HF disruption has been hypothesized to downgrade magnetic navigation during geomagnetic storms, which both produce HF and deviate Earth’s magnetic field, but it’s just as likely that it disrupts the sensory mechanism in some unavoidable mechanical way. Incidentally, I think it’s super cool that tiny single magnetic domain crystals, generated biologically, can evidently sense radio waves despite being just a few microns long. By comparison, HF radio antennas are built to match the radio wavelength of between 10 m and 100 m.

So, will space whales on Mars have their magnetic sense disrupted by red light during the day, then activated only at dawn and dusk? Perhaps, but the bigger problem is that Mars doesn’t have a planetary dipole magnetic field so animals will have to use the half dozen or so other navigational heuristics to find their way. Like us, they will cope.

Back to the Martian north pole. At length they transition from driving on mostly rock and sand to driving on mostly ice, both water and dry (CO2). The terrain is laminated from successive seasonal cycles, and exposed water is rotten on the surface from sublimation, separated by layers of seasonal dust deposition. In contrast to their extended journey and dry camp at Underhill, the pole provides a LOT of water. An ocean, really, frozen up there on the top of the world. The text specifies 5 million cubic km, which is 10 million times more than what is in the frozen craters on the Moon. The latest estimate specifies a mere 1.6 million km^3 (3x less than in the book), with a similar amount at the Martian south pole.

Crossing 82°N Deimos, the more distant moon of Mars, also drops below the horizon. Near the mouth of Chasma Borealis, they find a cache of ice-mining equipment dropped from orbit. Ann disapproves of this blight on the landscape, while Phyllis and George cheer to see something of recognizably human origins that embodies their ability to harness natural resources and put them to work.

The ice miner is not a Rodwell but a complicated mechanical contraption that bores a tunnel into the ice, passes back cores the size of hay bales, then melts, filters, and refreezes the ice for transport back to Underhill. The sound of its boring is barely perceptible unless the listener makes physical contact with the ice – due to an impedance mismatch Mars’ near vacuum atmosphere doesn’t transmit sounds very well.

Like the permafrost water ice mine, this ice miner seems both overly complex and at least 100x too small and 1000x too far away from the base. How do the trucks obtain the fuel they need to drive all that way? What powers the ice mine – the solar panels mentioned in the text would be in shadow at least half the year and, given its proximity to the western wall of Chasma Borealis, more than half the time even in summer. Unless dust is >10% of the ice, what’s the point of melting it to process it, especially given melting ice is incredibly energy intensive. If we’re going to melt the ice why not melt it in situ with a series of bore holes, as water is extracted in Antarctica.

Assuming a fleet of 10 trucks each transporting 10 tonnes of water and driving at 30 km/hr, 24.6 hours/day, a round trip of 16 days delivers 6 T of water per day. To install this much water capacity, we took 372 person-days of labor out of the available pool (6 people for an eight week trip).

US per capita consumption of water is 3.3 T/day. We’ll assume that the First Hundred are 10x more industrially productive than the average US citizen (requiring 10x as much water), but also that 90% of their water is recycled, putting Underhill’s demand at 330 T/day. That would require the borer to drill 150 m/day (while never hitting any rocks), and expanding the fleet size to 550 trucks, or 5.5 trucks per person. The American Dream! Despite the laughably ineffective nature of their water extraction process, Ann worries that the terraforming faction will warm the planet enough to melt the entire pole. Water’s latent heat of fusion is 334 kJ/kg, so melting both poles will require 10^24 J, a colossal quantity of energy. More than a mole of joules! Equivalent to 520 days of sunlight falling on the planet. The largest nuclear weapon of all time was a mere 2.4*10^17 J. We’d need millions of them to make a dent. Still, increasing Mars’ insolation and reducing thermal radiation is the key to terraforming, and little bit goes a long way.

Having accomplished their primary mission, the six immediately get into a bitter argument over whether, having come this far, they should also bag the north pole while they are there. Ann, Simon, and Nadia want to go, while the prospector three are, at this point anyway, immune to romance and see it as pointless. Naturally, the UN gets involved, Arkady threatens to make a supremely impractical supply drop, and in the end they split up and go anyway. To me it seems to be an argument for argument’s sake, but also a prelude to the coming fight on terraforming. There is only one planet and their visions for its future differ in fundamentally incompatible ways. Ann, as usual, loses the argument but she does get to go to the pole, walk around up there, and take samples. She does concede she would benefit from a thicker atmosphere to lower radiation exposure.

While they’re up there they have to employ a variety of navigation techniques to confirm their location. They do GPS checks with the brand new areosynchronous communications satellites, which is a bit dubious as first, equatorial areosynchronous satellites are below their horizon and second, while the Indian GNSS system uses geosynchronous orbits, they would need multiple satellites above the horizon simultaneously to confirm their position. While just three areosynchronous (areo = Mars, geo = Earth) are necessary for planetary communications everywhere except the poles, more like nine are needed to cover the poles continuously, and at least 12 to do continuous navigation services there too. By contrast, a single satellite in low polar orbit is enough to do complete position/navigation/timing (PNT) determination provided the team is willing to stay still for two consecutive passes. While the LEO orbital period is about 90 minutes, LMO is about 110 minutes. Waiting two hours for a position fix is easier than launching nine additional satellites, unless there are routine polar expeditions all needing navigation services! With enough math and some tolerance for error, even a single pass could be enough to get a bearing and range to the pole, after which the team could continue their drive using odometry.

Polar navigation is non-trivial! This is is similar to the trouble taken by Amundson and others during the heroic age of Antarctic exploration in order to confirm their location to an accuracy of a few miles, after which they rastered the area on skis to be sure they’d gone over the physical location!

Despite the sun not setting while they’re on the ice, their clocks, set to Underhill time, still time slip at midnight. One could imagine an epic party up there where rovers from every time zone on Mars converge on the north pole, each having a time slip one hour after the next. This reminds me of New Years celebrations wherein one must toast every different time zone at the appropriate time over a 24 hour period!

On the ice cap the landscape is especially stark, with a nearly flat white surface like Antarctica, the usual thin Martian sky, and occasional meteorites in sharp contrast on the surface. Meteorites are routinely discovered in Antarctica too, as they can be easily spotted at great distances lying on the ice. Ann remarks that Mars meteorites have gone to Earth and, occasionally, some from Earth on Mars. Perhaps they will find a chunk of Yucatan, blasted off by the impact that killed the dinosaurs?

In cold regions, ice crystals in the atmosphere reflect the sun’s light forming spectacular halos and cusps, which the polar team observes.

On their way back we get a discussion of the earliest terraforming concepts. Sax and Hiroko want to make windmills that convert ambient wind energy into heat, to be deployed all over the planet by dirigibles. This doesn’t make much sense as wind energy is ultimately converted to heat and radiated into space anyway, but we will see this soon becomes a plot device so we can maintain our willing suspension of disbelief. Sax also suggests dusting the polar caps with black dust to reduce their albedo and increase temperature. This is much more sensible than windmills because it actively amplifies solar heating with an almost 2-dimensional film coating, requiring very little material. Terraforming is discussed in more detail in later chapters, but for interested readers I have two blogs on terraforming, the most recent focused on using Earth-produced solar sails.

Merely increasing the temperature will lead to ice loss from the polar regions as the balance of sublimation and accumulation will shift in favor of the equator. To get liquid water on Mars, though, we also need additional pressure. This behavior is summarized in the phase diagram, where Mars’ surface pressure of 600 Pa is just below the triple point. Fortunately these two factors are linked, as higher temperatures increase sublimation of CO2 frozen out on the poles and in the regolith, and thicker CO2 also retains more heat, leading hopefully to a runaway greenhouse effect.

Mars’ smaller size affects the quantity of atmosphere needed in a few ways. First, lower surface area means less overall gas, though on a per-area basis it doesn’t change. Second, lower gravity means we need more gas for a given level of pressure, roughly 2.5 x more. And third, lower gravity means a greater atmospheric scale height, so one has to ascend much higher to have the same pressure drop one would experience say, mountaineering, on Earth. Low gravity and slow geology means that Mars has a lot greater variation in ground altitude than Earth – while some Earth peaks are 8 km high, nearly all the dry land is below 1.5 km in altitude. On Mars, most of the surface falls within a 7 km height range!

Back at the ice mine, Phyllis and her crew have assembled some ice blocks into a classic Greek temple, with columns and a cap. They depart together for the south, coming upon the permafrost well which has sprung a leak, shooting a column of black liquid water onto the surface where it steams and freezes. The planet is wet, and Nadia drew the first blood.

They roll back into Underhill after 62 days away, passing 5 km of industrial landscape – an impressive amount of mess for just 100 people! Nadia is immediately back into construction, with Hiroko asking about phosphorus on their journey, which forms the basis of an essential fertilizer increasingly rare on Earth, and a decision to retrofit the Underhill hab quad with a covered, pressurized and supremely labor intensive garden inside. Michel the psychologist seems aloof, and after 420 days on Mars, Arkady finally comes down from the questionably useful base on Phobos, only to endlessly criticize the ugliness of the construction as Nadia shows him around. Fortunately for Arkady, Ann is on hand to set a global high water mark for tactless, artless, unfiltered, supremely politically unsavvy remarks besides which he’s merely grumpy.

Nadia begins design of a newer, bigger hab which will also be entrenched and mostly underground but use mirrors to enjoy sunlight while retaining most of its radiation shielding.

Back to the terraforming debate. We get the first mention of specialized greenhouse gasses, here hexafluoroethane, to greatly enhance Mars’ ability to retain solar heat. The fluorocarbons, chemically similar to Teflon, have both excellent thermal opacity and long term stability in the atmosphere. While some synthesis methods involve toxic precursors, their manufacture would have to be as automated as anything else, most likely revolving around a big robotic mine of a fluorite deposit.

As the debate progresses, factions become personified within the main characters of the book, who in turn become more prominent. This is underscored by Iwao’s new description as Hiroko’s assistant, which is quite distinct from personnel descriptions in the previous chapter that characterized every member of the First Hundred as prominent in their own right. Ann is a “red,” and has almost no allies. She argues in favor of leaving Mars as it had been, bringing forward arguments like the potential impact on the Antarctic Treaty, or uncertainty about whether Mars already has life that they could avoid contaminating. Of course, we now know a good deal more about life surviving in vacuum or on Mars and it is a near certainty that our Mars landers have transported large numbers of Earth bacteria to Mars, which could survive while dormant, but would be unlikely to be able to reproduce on the surface, in part due to cold and chemistry, and in part due to overwhelming ultraviolet light. Beneath the surface is another question, and unfortunately, some parts of various landers (including the ill fated Mars Polar Lander) have hit the surface quite hard. DNA PCR tests for life have found evidence for the overwhelming majority of bacteria and archaea that can’t be cultured, including a species of bacteria found only in a handful of sterile clean rooms on different continents, that turned out to eat the disinfectant! In other words, when humans landed on Mars, any pretense of sterility was lost forever. That said, within KSR’s Mars Trilogy, Mars was always without life until humans arrived.

In contrast, Sax points out that advocating for delaying the decision until sufficient certainty can be reached on the life question is also a decision, and despite it seeming to be a reasonable position, it actually means “do nothing forever,” which is an interesting variation on NIMBY culture. He then brings forward the typical arguments for terraforming and industrializing the planet, namely manifest destiny, and developing a material basis for independence. At this point, at least, no-one seems to argue in favor of terraforming Mars as an act of love and artistic creation. I think a terraformed Mars would be the most beautiful thing humans have ever created.

Meanwhile, around one Mars year after landing, Underhill is nearly complete. All the cargo has been unpacked, installed, and commissioned. The first outpost on Mars is self-contained and nearly self-sufficient, and it took just 50,000 human days of work to build, roughly equivalent to $10m in payroll costs. There are single episodes of television that cost more to produce! This presents a problem, because if just 50,000 human days of work are needed, with 2027 technology, to build a self-sustaining town on the hostile environment of Mars, then that has deep implications for economics on Earth.

Mars is a hostile environment – it’s not possible for humans to sustain life there with some medieval level technology and a small group of mostly generalists, no matter how well provisioned and trained. Even on Earth, groups as small as 100 people typically cannot maintain a level of technology beyond the neolithic. Metallurgy and even agriculture are really tough. So if 2027 tech makes this possible, it represents an extremely radical compactification of the industrial stack. Far from needing O(10-100 million) people to sustain industrial civilization, which is the status quo in 2023! Given that much of the labor performed in Underhill is driving screws and tractors rather than instantiating army after army of completely autonomous cybernetically connected robots to lift human operators five levels of abstraction above physical manipulation of matter, this is something of a problem. Having raised the issue, we will now wave our hands and realize that the story is about the First Hundred, not the First Hundred Million, and is primarily concerned with politics and revolution, rather than mass production, specialization, and logistics. That book is still waiting to be written – maybe Neal Stephenson can take a crack at it?

Vlad and his team are still doing gain-of-function research on algae. Arkady says they should just scatter them on the surface, and sees the potential release of engineering organisms as a focal point for his campaign to localize power and self-determination within the First Hundred and more specifically his faction. He grows frustrated at the prevalent scientific liberalism, with its studious “apoliticization” and unwillingness to grasp power and fate, an issue that science still struggles with today. The genetically enhanced algae generates a lot of “commentary on the scientific nets,” which is clearly KSR’s prediction of science Twitter.

The final act of this chapter concerns Nadia and Arkady’s mission to take Sax’s autonomously produced heat windmills and scatter them over the surface of the planet. It is curious to me that while KSR sidestepped the labor and resource intensity of producing thousands of otherwise useless gizmos, actually distributing them on the planet is incredibly labor intensive, taking a crew of two months to drop, at most, a few hundred. Further, given that their overly-complex mechanism just generates local heat, it is unclear why it is necessary to distribute them around the planet, when one could just as easily set them up in some local wind gap near Underhill. Why? Because the readers want to join Nadia and Arkady on a Zeppelin flight around the entire planet. That’s why!

Speaking of which, we get a description of the Arrowhead dirigible, which appears to be a pressure stabilized internally trussed airship similar to the Zeppelin NT, albeit somewhat larger. Yet, 120 m wide, 100 m long, and 40 m tall it is only big enough to displace just 4.8 T on Mars’ atmosphere, compared to ~250 T for similarly sized Hindenburg class airships on Earth. 4.8 T is not a lot to work with, given that it must include the mass of passengers, cargo, food, life support supplies and equipment, the entire structure and envelope of the blimp, and its internal lifting gas, which is hydrogen. By comparison, a Pilatus PC-12 weighs about this much. This works out to a surface density of just 143 g/m^2, equivalent to a sheet of paper. I’m inclined to believe that giant surface rovers would work better for this task, but they are not as cool!

The airship has turboprops on wing tips and under the gondola, powered using solar panels on top. This is conceptually possible with extremely thin panels, except that a solar powered airship couldn’t fly at night, and the quantity of solar power available (about 2.6 MW at best) is sufficient to drive the airship at just 35 m/s, perhaps 3x faster than a rover. This is somewhat faster than an equivalent system on Earth, because Earth’s atmosphere is thicker and makes more drag, but it’s also thick enough that Earth airships are actually possible to build.

Their route takes them east across a grab bag of geographic features (see the attached .kml file for rough routing), averaging just 10 km/h in the text, and flying about 100 m off the deck and the horizon 50 km away, though 25 km seems closer to the mark at that altitude. Many features are called out by name that wouldn’t be visible unless Nadia and Arkady were right on top of them. For example the larger volcanoes and craters are so enormous, and slope so gradually, that their shape is overwhelmed by the curvature of the planet.

The windmills themselves are a 5 kg magnesium box with 4 vanes on top, driving a vertical axis windmill into a generator and from there to heating coils. Of course, if converting mechanical motion to heat is all that’s required, the intermediate step of generating electricity is superfluous – a brake or oil damper would work just as well while being substantially cheaper. Nadia and Arkady heave to and lower a handful each day, using a “bomb bay” airlock and winch. Again, this seems like a lot of effort for something that could potentially be deployed by throwing them out the window, or dropping them off the back of an automated rover, especially given the mission is, again, taking two people two months to drop perhaps just 150 or so windmills!

They cross the massive outflow channels at the south end of Chryse, each representing an ancient flow 10000x the Mississippi, giving some idea of the violence of Mars’ watery past. They pass the Watney Triangle, then take in the enormous craters of Schiaparelli and Cassini, which gives Sax an opportunity to suggest stealing icy moons of Saturn and dropping them on the planet to add volatiles and heat. Nadia points out, quite rightly, that there is plenty of ice here on Mars already – and there is! Much more than all the moons of Saturn combined, and already in the right place.

Their route takes them east through Isidis and then over the Cerberus Fossae (site of most of the Marsquakes detected by InSight) south of Elysium, though their peaks would have been invisible on the given route, and probably not visible anyway from an airship with somewhat restricted altitude. This is a recurring problem with landscape descriptions in the Mars Trilogy – the horizons are tight and (usually) the viewpoint too close to the surface to see much more than the extremely local area. This is exacerbated by the fact that KSR’s reference maps were drawn using imagery with 300 m resolution, so all the smaller features they would have been able to see and relate to were simply not known until about a decade after the Trilogy was written, when more capable orbital cameras flew to Mars. It is cool, though, that their route takes them so close to Insight and MSL – perhaps they could stop by and dust off the solar panels and reset the mole?

As they leave this region to the east passing towards Orcus Patera, the plot thickens! Nadia drops a windmill by accident and rather than just lowering another and getting on with it, decides to investigate the damage, lowering herself on the same winch that just malfunctioned and dropped a disposable windmill. It turns out that they contain a diabolical mechanism intended to release some of Vlad’s algae once the windmill has warmed the local area enough for it to maybe survive. It is then revealed that there have been 10-20 other dirigible trips to drop the secretly algae-fied windmills all over the planet, thus doing what Arkady had advocated though apparently without his knowledge. Again, it is weird they couldn’t do this a half-hour drive from Underhill but … it’s a story.

We get our first mention of Johnny Appleseed, Paul Bunyan, and Big Man, some mythical archetypes that come to inhabit the alien landforms of the planet and give them context, to the humans who first live there. We also get a discussion of other terraforming methods, including giant mirrors to extend the day, carbon black on the icecaps, releasing of areothermal heat by drilling giant holes in the crust, and bombarding the planet with lots of icy asteroids. All of these add some heat, of course, but optimal capital allocation forces us to understand what methods add the most heat per unit resources invested. For an Earth-based program, that is lots of mass produced mirrors launched from Earth, and for a Mars-based program, it is most likely synthesis of perfluorocarbon greenhouse gasses to trap heat in the atmosphere.

Their consternation about the deception wrought by Sax’s team at their expense is cut short by the sudden development of a huge dust storm, a standard procedure to move the plot forward in any book set on Mars. Their course takes them (improbably, for an airship) over the Tharsis rise back towards Underhill. John sends them a weather report with a satellite photo, displayed on their TV screen. Remember, in 1992 the Internet hadn’t really evolved far enough for image-rich webpages to exist, so this can be thought of more as a wireless fax or television transmission, via the Mars TDRS satellites.

At this point in the story, plot is occurring and the technical details become a bit shaky. First, we learn that the turboprops are not actually driven by a turbine, but instead by batteries (which would be impossibly heavy) charged by solar. In an earlier edition of the text, Nadia repurposed some windmills to generate electricity, but balloons move with the air stream and wouldn’t generate any relative wind of their own, so KSR tweaked the sequence to enable deployment of more solar panels, which apparently were just lying around somewhere in storage consuming some of their incredibly limited 4.8 T payload. The airship also has a supply of hydrazine to power the bomb bay airlock and the water recycler, but it’s not clear how or why, if the rest of the systems are electrical.

During this dust storm, insolation drops to about 15% of normal. Mars dust storms, we now understand, can get much more severe than that, with Opportunity killed off by a storm that blocked out more than 99% of the sun’s light.

Nadia has an awesome sequence walking around under the airship in the storm to attach more solar panels on the underside (since what light there is is mostly isotropic), watching smoke-like dust grains zoom by in clouds at imperceptibly high speeds, yet experience almost no ram pressure due to the low atmospheric density. The airship itself gets thrown around, though, as it is so light it has far less momentum per unit volume than a human. Roughly 100,000 times less!

As they approach the ice rover road established earlier in the chapter, they struggle with dust-induced radio interference while coordinating an extraction via robotic truck. This indicates that their radio communication is probably analog in specific bands, as modern digital radio (such as what is used for mobile phones, satellites, Starlink, etc) can actively adjust bandwidth, encoding, power, and error correction to ensure the channel contains as much data as is physically possible.

As their journey nears its end, their little airship cabin somehow gets dust in it (perhaps via cycling of the airlock, despite the huge pressure gradients) and they stink of sweat and hydrazine. Nadia employs her intuitive understanding of mechanical engineering to cut out all the less structural parts of the gondola. It turns out that the strongest beam for some given quantity of material puts most of that material a long way from the center. For example, the “I” beam cross section has just a narrow web joining the two horizontal parts, ensuring that the constituent material is equally close to failure from buckling or inelastic deformation in every part of the entire beam. That is, the ideal beam or structure makes every last part of it work as hard as it can without failing, and with no wasted material. Obviously, some structures (roads, buildings) can afford much higher safety factors in service of lower costs, but rockets are so marginal in terms of their ability to work at all that they really have to use the lightest possible materials and really make them work.

Dreading their return to Underhill with the forbidden knowledge of an illicit algae release attempt, the awkwardness is averted when they hear that the UN has approved all terraforming efforts and is sending up 1500 new people across three new bases, representing new countries not present in the First Hundred.

This post took longer to write than I had expected, but I think future chapters will have less technical detail to discuss. I hope!

2 thoughts on “Mars Trilogy: The Crucible

  1. The mars trilogy is one of my favorite books of all time, but the damn windmills almost made me give up on my first read. Thankful I kept reading – despite the technical whoppers KSR is so prone too (I’m also reminded of everyone being required to eat extra salt in “Aurora” because of an excess supply – why not just put it in a pile somewhere?) the mars trilogy is a towering achievement.


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