This is an attempt to work out the range and typology of human sites related to space exploration. As with everything, once you start to try and pin down categories you find that there are grey areas and ambiguities that have to be resolved, definitions that bleed into each other, aspects that you didn't anticipate. In these blurred spaces you can find out something about your own concepts about how the world works. So let's see how this unfolds.
There are several ways to divide these sites up. It could be location: is it on Earth, orbit, a planet? It could be function: launch, residential, data gathering, data receiving. It could be degree of autonomy: is it a far-away robot, or something that requires people to operate?
We could divide space places into closed and open, depending on their relationship with the environment around them eg orbital habitats are closed, terrestrial places are open (to different degrees). Simulated habitats translate one type of site into another environment. We could also classify them by the social forms they support - matrilocal, endogamous, communal, capitalist, carceral, arnarcho-syndicalist (you get the idea). I would think it likely that space occupation will result in new social and political forms. This leads me to the question of what type of being or state of being goes with each of these places ie what is the kind of person who uses it, and under what conditions?
We could also characterise them by 'segment' - ground, space and user, although I am becoming increasingly dissatisfied with the idea of the user (perhaps more on this another time). Most (but far from all) terrestrial space places will be part of the ground segment of a space mission. And so far, the user segment is also completely terrestrial. This too, we presume, will change.
And finally, we could classify these sites according to the frequencies or wavelengths they utilise - optical, laser, radio, microwave etc. Each frequency requires distinct technology and sometimes a unique sensorium.
Each place will be in use, abandoned, or perhaps a combination of both.
We could divide space places into closed and open, depending on their relationship with the environment around them eg orbital habitats are closed, terrestrial places are open (to different degrees). Simulated habitats translate one type of site into another environment. We could also classify them by the social forms they support - matrilocal, endogamous, communal, capitalist, carceral, arnarcho-syndicalist (you get the idea). I would think it likely that space occupation will result in new social and political forms. This leads me to the question of what type of being or state of being goes with each of these places ie what is the kind of person who uses it, and under what conditions?
We could also characterise them by 'segment' - ground, space and user, although I am becoming increasingly dissatisfied with the idea of the user (perhaps more on this another time). Most (but far from all) terrestrial space places will be part of the ground segment of a space mission. And so far, the user segment is also completely terrestrial. This too, we presume, will change.
And finally, we could classify these sites according to the frequencies or wavelengths they utilise - optical, laser, radio, microwave etc. Each frequency requires distinct technology and sometimes a unique sensorium.
Each place will be in use, abandoned, or perhaps a combination of both.
As you'll see below, I've decided for this preliminary exploration to use military, civil and commercial, location and segment. As I'm familiar with them, I've included a lot of Australian examples.
I'm also interested in the gaps that appear when we map the relationships out. For example, there is a whole class of planetary occupation sites that are not yet in existence. There are interplanetary niches that we're waiting to see filled.
For each of these categories we could ask different research questions. Perhaps I will put some of these in.
I certainly don't see this taxonomy as an end in itself - just a way to explore concepts. And I guess I'm only including places that are created by human intervention. This leaves out places where extra-terrestrial materials have crashed to Earth (like meteorite craters). Some of these are the focus of much human activity and emotion, so perhaps I will have to revisit this.
I'm also interested in the gaps that appear when we map the relationships out. For example, there is a whole class of planetary occupation sites that are not yet in existence. There are interplanetary niches that we're waiting to see filled.
For each of these categories we could ask different research questions. Perhaps I will put some of these in.
I certainly don't see this taxonomy as an end in itself - just a way to explore concepts. And I guess I'm only including places that are created by human intervention. This leaves out places where extra-terrestrial materials have crashed to Earth (like meteorite craters). Some of these are the focus of much human activity and emotion, so perhaps I will have to revisit this.
The order of these places is sort of how they occurred to me. I'm sure they could be better organised, alphabetically maybe, but this is what you are going to get.
- Military
- Civil (including amateur and scientific)
- Commercial
Things don't always get into space by rocket alone - they can also go by balloon, rockoon, and aeroplane. So some launch sites will also be airfields, such as Vandenberg Air Base in the US.
There are landing sites for re-useable space vehicles, like the US Space Shuttle and the SpaceX booster rockets. The landing site may be the same location as launch site but not necessarily eg the Maralinga airstrip in South Australia, which was qualified as a Space Shuttle emergency landing site, but was never used for that purpose.
Spaceport: what makes a spaceport? I think this is a place where both launch and landing happen - a place of transit like an airport or harbour. A spaceport seems like it should be civil/commercial. It's a non-place (following Marc Augé), or a liminal place, where people are transitioning between Earth and space. There are a few places on Earth which are called spaceports, but they aren't really by this definition - the name is aspirational rather than describing their function.
Residential: Residential facilities accompany many launch, tracking and R & D sites. This is where people live, either temporarily or permanently, while they work at the facility. They range from whole towns to a single house. There are probably two kinds: the accommodation used during the construction of a facility, which frequently will not survive, and the accomodation used during the operation of a facility.
There are also gendered differences in residential sites. Some are meant to be for families; others are male-only, like at France's launch sites in Algeria. There may be gender-exclusive places within a larger facility eg men's and women's accommodation and messes as there were at Woomera. Residential facilities can also be military, civil and commercial.
Human graveyard: these are attached to space towns or residential areas, so the occupants will be a subset of the larger population. Woomera has its own cemetery, and the burial data reflects the particular conditions of the place, with very high infant mortality. Other cemeteries may reflect the gender of the workforce. There may be distinct forms of memorial that reference the space connections of the deceased.
Residential: Residential facilities accompany many launch, tracking and R & D sites. This is where people live, either temporarily or permanently, while they work at the facility. They range from whole towns to a single house. There are probably two kinds: the accommodation used during the construction of a facility, which frequently will not survive, and the accomodation used during the operation of a facility.
There are also gendered differences in residential sites. Some are meant to be for families; others are male-only, like at France's launch sites in Algeria. There may be gender-exclusive places within a larger facility eg men's and women's accommodation and messes as there were at Woomera. Residential facilities can also be military, civil and commercial.
Human graveyard: these are attached to space towns or residential areas, so the occupants will be a subset of the larger population. Woomera has its own cemetery, and the burial data reflects the particular conditions of the place, with very high infant mortality. Other cemeteries may reflect the gender of the workforce. There may be distinct forms of memorial that reference the space connections of the deceased.
Technology Graveyard: there's a place on the bottom of the ocean, called Point Nemo, the furthest point from land in any direction, where satellites, rockets and space stations are de-orbited. There may also be specific places where old spacecraft and infrastructure are buried/stored - perhaps I would classify the Woomera Rocket Park with all its rocket wreckage a graveyard site. There are certainly burial pits at the old Orroral Valley tracking station in the ACT.
Tracking: Here we get a lot of overlap with astronomy. Tracking antenna can be isolated installations or part of a larger tracking station with many antennas. The antennas may be used both for satellite tracking, command and telemetry, and for radioastronomy. Parkes is a good example of such a mixed-use antenna. Tracking stations are not just the antennas, though: there is usually a lot of other infrastructure and buildings. Like launch sites, tracking facilities can also be military, civil and commercial. They are directly linked to the spacecraft they track and command in space, so you could argue that they are part of a multi-segment site.
Laser ranging: this may be performed by equipment which is part of a larger facility, or stand-alone. eg as at Orroral Valley in the ACT. Lasers are ranged to satellites and interplanetary places, such as the Moon. So you could say laser ranging facilities are also multi-segment sites with parts both on and off-Earth. I will have to remember to put laser ranging targets in the planetary surface section of this list.
Laser ranging: this may be performed by equipment which is part of a larger facility, or stand-alone. eg as at Orroral Valley in the ACT. Lasers are ranged to satellites and interplanetary places, such as the Moon. So you could say laser ranging facilities are also multi-segment sites with parts both on and off-Earth. I will have to remember to put laser ranging targets in the planetary surface section of this list.
R and D (Research and Development). These may be places that overlap with academic institutions. They may also be part of other facilities. The Mullard Space Science Laboratory in the UK is an example of a space R & D site. The EOS space debris company shares facilities with the Mt Stromlo Observatory near Canberra. R & D covers experimental facilities like microgravity drop towers. And of course, they can also be military, civil or commercial.
Test facilities: these are where spacecraft and equipment are tested before going into space. They could be for satellites or rockets and include static test stands, clean rooms, anechoic chambers, vibration tests. An example is the Advanced Instrumentation Test Centre at the Mt Stromlo Observatory. Another is the Spadeadam site in the UK where rockets were static-tested. Test facilities may be part of site complexes, such as the White Sands launch range in the US.
Test facilities: these are where spacecraft and equipment are tested before going into space. They could be for satellites or rockets and include static test stands, clean rooms, anechoic chambers, vibration tests. An example is the Advanced Instrumentation Test Centre at the Mt Stromlo Observatory. Another is the Spadeadam site in the UK where rockets were static-tested. Test facilities may be part of site complexes, such as the White Sands launch range in the US.
Manufacturing: this where spacecraft components and materials are manufactured. There may be a lot of overlap here as such facilities may make stuff for other industries too.
Museum/rocket park: Woomera is a great example of this with both a heritage centre and a rocket park. The museum may be dedicated to space, or have a space component, like the Powerhouse Museum in Sydney. Space museums are both places where a lot of material culture related to space resides, and an interface where the public engages with space history and technology. Given that so many space sites are high security and cannot be visited by the public, this becomes even more important.
Playground rocket park: Unlike the rocket parks where actual rockets are put on display, these rocket parks are playgrounds for children. The rockets are an idealised metal climbing apparatus, frequently with a slide attached (Gorman 2018). They are common in the US, Australia, and the Eastern bloc, with an unknown presence in western Europe and the UK.
Playground rocket park: Unlike the rocket parks where actual rockets are put on display, these rocket parks are playgrounds for children. The rockets are an idealised metal climbing apparatus, frequently with a slide attached (Gorman 2018). They are common in the US, Australia, and the Eastern bloc, with an unknown presence in western Europe and the UK.
Crash landing site: These are frequently isolated locations, unlike the technology graveyards. The first such sites might be the craters where V2 rockets crashed in the 1940s, both in testing and in delivery of their bomb payloads. See here for a story on a V2 crash site in Mexico. If there is more than one crash landing in a location, as you find with some V2 target and test areas in Europe, then there is a landscape of craters. This is a sort of analogue landscape (see below) but also an Anthropocene landscape where human activity mimics 'natural' processes such as meteorite strikes. The crashed material may or may not still be present at the place. The site may also include debris fields from re-entry, or the locations where 'space balls' , pressure vessels of made of titanium alloy, land.
Protest site: many military installations provoked a community response, so they become loci of contested values. There are often remains from the protest camps. For example, there were many protests around the US military surveillance antenna at Nurrungar in South Australia. The Apollo crewed missions resulted in protests at the Cape Canaveral launch site.
Crew training sites: an example is the Russian Star City. These will often contain equipment to mimic or simulate space environments, such as neutral buoyancy tanks, as well as residential and teaching facilities. It just occurs to me that terrestrial places have facilities to mimic microgravity, and space stations have facilities to mimic Earth gravity (I'm thinking of treadmills and weights) - a kind of inverse gravity.
Crew field training sites: Astronaut training starts on the ground. There are numerous locations where astronauts and cosmonauts underwent survival training, eg in Hawaii and Nevada in the US. Sometimes these are also analogue landscapes. Generally these will be for professional training, although some amateur organisations like the Mars Society also have field training exercises.
Analogue landscapes: these are places on Earth which have some of the characteristics of other-planetary landscapes, such as the Moon and Mars. While they may also be used for training astronauts, they're used for research, testing equipment and experiments in off-Earth survival by amateur and civil groups too. For example, the amateur Mars Society of Australia uses the Arkaroola analogue landscape in South Australia.
Analogue habitats: these are different from analogue landscapes because they are deliberately designed to replicate social and environmental conditions of living in space, generally inside a facility. Examples are Biosphere 2, and Hi-SEAS. They can also be test habitats, made out of a spacecraft not intended for launch, which are used at human spaceflight centres such as those NASA operates. So here we have civil and amateur habitats.
There are other habitat types not designed specifically to replicate space conditions, but which are often used as an analogy because they are confined with small groups of people - such as submarines, polar research stations and prisons. I'm not including these as their intent is not to simulate space.
Simulated landscapes: this includes movie sets, such as the Star Wars one in Tunisia, which are intended to represent another planetary environment. We could also include Mars Yards - enclosed recreations of Martian landscapes often used in education and research - such as this one.
Amateur gravity simulation: Amusement parks often have drop towers, centrifuges, roller coasters and gravity rotors, all of which are similar to astronaut training equipment. We could divide this into those which allow the user to experience another gravity situation, and those where an audience observes the simulation, like watching a circus. Circuses feature gravity-defying acts, such as the trapeze, at which one can marvel. For training, skydivers have some kind of air tunnel that allows them to be suspended in the air. Balloons allow regular people a high altitude experiences.
Domestic: These are places or objects that enable a non-space professional to use space services - the user segment. They include satellite dishes on houses and buildings, smart phones, television, and GPS units, and can be static or mobile.
Simulated landscapes: this includes movie sets, such as the Star Wars one in Tunisia, which are intended to represent another planetary environment. We could also include Mars Yards - enclosed recreations of Martian landscapes often used in education and research - such as this one.
Amateur gravity simulation: Amusement parks often have drop towers, centrifuges, roller coasters and gravity rotors, all of which are similar to astronaut training equipment. We could divide this into those which allow the user to experience another gravity situation, and those where an audience observes the simulation, like watching a circus. Circuses feature gravity-defying acts, such as the trapeze, at which one can marvel. For training, skydivers have some kind of air tunnel that allows them to be suspended in the air. Balloons allow regular people a high altitude experiences.
Domestic: These are places or objects that enable a non-space professional to use space services - the user segment. They include satellite dishes on houses and buildings, smart phones, television, and GPS units, and can be static or mobile.
At this point, I should start making a table where I compare terrestrial, orbital and planetary sites, just to see how they map out against each other. How many are common between all three locations? I could then flag which types exist already, and which have had archaeological work done on them. Stand by for this (it might not happen any time soon).
Defensive: this is a defensive structure meant to protect against assault from space-based weapons. Are there any? I don't actually know! I suppose we could count here bunkers meant to protect against nuclear and other weapons delivered by ICBMs and IRBMs, which are not strictly space weapons.
But is the site an orbital band eg Low Earth Orbit, which contains an assemblage of different objects, or the object and its environment by itself, as a unit? In which case, where are the boundaries of the object?These are like the issues of site and off-site archaeology on Earth. Sites can be defined by a decrease in artefact density, and we certainly have that in space - there are some regions of very high orbital density, surrounded by areas of lower density.
At the end of the day there is only so far you can get with a terrestrial analogy so perhaps the best thing is just to abandon it altogether. So if I'm not going to have a site, what is the unit of analysis? This matters because it is the relationship between things that is of interest to the archaeologist.
Maybe they're like particles in an atmosphere, so we have to model the relationships in a volume of space. Perhaps it's a matter of how much that volume is made up of 'natural' and 'manufactured' particles or molecules. This also gives us a measure of comparison with different regions of space, both 'natural' and 'cultural'. What does a manufactured atmosphere look like? It would have a difference chemical composition compared to Earth's, which of course has changed over time too. The constructed atmosphere inside an orbital or planetary habitat (as an archaeological artefact) would be different to the naturally evolving composition of open space once manufactured materials enter it.
I'm going to free-wheel with this a little and see where it gets me.
Robotic orbital: to be robotic orbital, an object must be automated, or have had the capacity to receive and/or transmit data. So this means satellites, rockets and rocket stages, space telescopes and I don't know what else. Like launch sites, these can be military, civil or commercial. Robotic orbital includes delivery vessels which transport materials and goods between habitats, planets and moons. We already have robotic craft which are used to supply the International Space Station. There may be some overlap with industrial here.
(My next question is what is robotic terrestrial? Liam Young has written of machine landscapes, places designed just to be used by machines, unfriendly to humans. Perhaps they would not even bother with a breathable atmospheres or temperatures comfortable for the human body. There would be no walkways or steps if humans didn't ever have to go there. To make it into this blog post, however, they would have to be space-related).
Passive orbital: Some satellites are not robotic. These include LAGEOS 1 and 2, satellites covered in retroreflectors for bounding lasers off; the Westford Needles; metallised balloons like Echo 1 to bounce radio waves off; and perhaps artistic installations like the Humanity Star (no longer in orbit) which are meant to visible to the naked eye. They have no moving parts and do not themselves communicate. Elon Musk's red Tesla sportscar falls into this category too.
Passive orbital: Some satellites are not robotic. These include LAGEOS 1 and 2, satellites covered in retroreflectors for bounding lasers off; the Westford Needles; metallised balloons like Echo 1 to bounce radio waves off; and perhaps artistic installations like the Humanity Star (no longer in orbit) which are meant to visible to the naked eye. They have no moving parts and do not themselves communicate. Elon Musk's red Tesla sportscar falls into this category too.
Human orbital: habitats and space stations. Is this the same as residential? Is there a difference? Perhaps not, as residence and work are the same place in space. Or at least they are at the moment, in the International Space Station and its Russian predecessors. Are there human-occupied places which are neither? There are empty experimental space stations, like Genesis I and II. There are space station types which have been hypothesised but never existed, like spinning wheels. You might have in the future little combat pods or hibernation units. A space suit, occupied in orbit, might constitute human orbital.
At present we only have civil space habitats, but in the future there may be military ones and independent ones too - like utopian colonies on Earth. Commercial habitats may be for space tourists or people working in orbital manufactories. In this case work is separated from residence.
As an extension of this thought, it might be that divisions between work, residence and leisure are different or non-existent in habitats. We may need to define what is considered work. For example, on Earth, there are no activities related to maintaining one's body in a different gravity. Do such activities count as work? They sustain existence but they are also 'work' in both the physics sense, and something you don't do for leisure, as going to the gym or for a run is on Earth.
Here are some further ways to categorise human orbital sites - all of which can also be military, commercial, or civil.
Single occupancy: a one-person habitat, pod or hypersleep carrier. Designed to sustain a single human life in space conditions.
Multiple occupancy: a space station, habitat or even hotel, designed for more than one person. There might be different classes of this too - up to 10, 10 - 20 people, 20-30 people, etc. Currently, no space stations have ever had a crew of more than 13 people, so I guess we don't have direct experience in scaling designs to accommodate more (although see Scharmen 2020 for a discussion of the architectural considerations of such habitats).
These habitats might be purpose-built, that is designed specifically for a certain number of people and a certain function. They may be scavenged: made up of discarded components and materials from other spacecraft. Another possibility is adaptive re-use, where a habitat made for one function is re-purposed for another, such as a military barracks being converted into a hotel or an upper rocket stage into a habitat. Habitats may be licensed or legal, or illegal - space squatters, or even pirates.
At the moment, all space habitats have been designed on Earth, in full Earth gravity. While some like Mir and the International Space Station have been assembled in orbit, each module is defined in terms of shape, size and weight by the limits of launching on a rocket and by its engineering heritage.
Space habitats designed and manufactured for orbital use only, with no transit phase, will likely look extremely different. We might call it the difference orbital migrants and orbital natives. For example, the cylindrical rocket body may no longer be the archetype, although a curvilinear architecture will prevail due to the requirements of a pressurised volume.
Human orbital habitats will also be defined by gravity. Some will be micro- or zero-gravity, some will be spinners (ie they have gravity from spinning, and others will be multi-gravity, containing sections with different levels of gravity. Such a habitat is described in Orson Scott Card's novel Ender's Game (Eriksen 2020). Obviously the nature of the gravity environment will have a big influence on the design.
Animal orbital: animal habitats or animal spacecraft. Of the latter, we have already had many orbital spacecraft which took animals into space. I guess here I mean ones which were only for animals, like Laika the dog, rather than ones which humans and animals share. Could there be space habitats which are independent animal colonies, like autonomous animal breeding stations? What might a goat habitat look like? Or one for crickets? I might ask here which animal species are better adapted for different types of gravity. Birds have very porous bones - perhaps they are more adaptable in terms of maintaining bone density in lower gravity. There must be a lot of research on this (I'll look at some point).
Gardens: I think I'm defining these as vegetated orbital spaces designed for pleasure or recreation. Flowers grow here, not just edible ones. These are for people to be in rather than producing some essential for nutrition. Or perhaps they're like botanic gardens, demonstrating the vegetal diversity of empire in space. They might be for teaching about life on other gravity worlds or nostalgic places to experience a little bit of an Earth that orbital populations might never visit.
Farms: these are purely for growing products to provision humans, or other animals to provision humans. Konstantin Tsiolkovsky imagined orbital greenhouses attached to the space habitats, the verdure pressing up against the glass in its abundance.
Industrial: this might include propellant depots and manufactories; solar energy producing arrays; chemical/pharmaceutical factories to produce medicines best made in microgravity; storage or stockpile orbits; waste processing facilities; factories for making products for use by orbital populations. They may use local materials, for example, derived from the Moon or asteroids, or recycle discarded materials in orbit. This one might need to be broken down into separate categories but I'll leave it parked here for the moment.
Graveyard, robotic: the most well-known example is the GEO graveyard orbit, where old geostationary telecommunications satellites are boosted to keep them from causing damage to functioning spacecraft in GEO. There don't seem to be any others at present; however, some have suggested that LEO is unsavable, and might as well be turned into or considered a graveyard orbit while we migrate satellite functions to MEO or even back to the ground.
Lagrange points have also been proposed as graveyards or museum locations. We might ask if there is a difference between an orbital museum and an orbital graveyard. How would you curate it? Future robots might consider these graveyards as their cultural heritage (see Spennemann 2007).
Perhaps in future there will be graveyard orbits around other planets. Each planet has its 'geostationary' orbit - for example, the areostationary orbit around Mars. There is nothing human in it though!
Graveyard, human: We don't actually have one of these yet! It's possible in the future you may have isolated bodies in orbit, which does not constitute a graveyard as such - perhaps more like an unmarked burial on Earth. Bodies may be ejected from space habitats rather than buried on Earth, perhaps accompanied by a ritual. Perhaps they will have some kind of signal to flag them as sacred, like a nuclear one, so that their bodies are not desecrated by space travellers who stumble across them. How would we design grave memorials for space?
As for a location where there is more than one body in orbit, perhaps there will be a designated cemetery orbit in future. Perhaps it will be very low: let atmospheric drag dispose of the body in a natural cremation. Perhaps there will be a giant cemetery spacecraft, constructed specially for this purpose. There are already services which send people's ashes into orbit, but these re-enter very quickly. Only Eugene Shoemaker has mortal remains on another planet.
Identifiable debris: this is a catalogued debris object; origin and function known. An example is a whole non-working satellite, or something like the debris from Fengyun 1C, over 3000 pieces of which are tracked. One estimate is that there is currently over 35, 000 pieces of identifiable debris over 10 cm in size. Identifiable debris is dependent on the limits of detection with current technology, so the number can change by the addition of new debris or by changes in tracking technology. The higher something is, the bigger it needs to be detectable from Earth.
A commonly accepted definition of space debris is an object which does not have a purpose now or in the foreseeable future. I have some issues with the designation of debris or junk, which are outlined in my book (Gorman 2019) - for example, some non-working satellites have a social purpose. What gets classified as debris might vary depending on who you consult.
Diagnostic debris: a catalogued object; origin unknown, but function known. A piece of thermal blanket, for example, could have come from one of any number of spacecraft, so we don't know its origin. However, we do know what it is, and we can use this information analytically. What proportion of space debris is thermal blankets or fragments of them? This would then tell us something about the robustness of their attachment to the spacecraft, and the frequency with which they come loose.
This might also include biological debris: parts of organisms, eg DNA, waste, ashes, which may have some analytical potential.
Unidentifiable debris/undiagnostic: What I'm calling undiagnostic debris - by analogy with the archaeological study of ceramics or bone - is fragments of space junk of which the origin is unknown or unidentifiable - that is, we don't know what spacecraft it came from. Moreover, we don't know what function it performed. However, in the future, it might be possible to provenance unidentifiable debris by chemical or mineral analysis by spectrometer. This relies on certain nations or manufacturers using materials with a distinct chemical signature.
Indeterminate: this is a category used in archaeological artefact analysis. It means you really can't tell what something is. There are no diagnostic features but there is nothing that rules it out either. In space, one category of indeterminate objects are those which we can't tell are human-made or natural. This will sometimes depend on the quality of observational data, and could change with time, as a closer view is available or other analytic data. It's not always easy to tell 'natural' objects from 'cultural' objects. Recently, a near-Earth asteroid appeared out of nowhere and turned out to be the upper stage Centaur rocket from the launch of Surveyor 2 in 1967. There's also objects like Snoopy, which were lost, found, but not definitively identified through lack of close observation data.
The International Astronomical Union's Minor Planet Centre publishes the Distant Artificial Satellites Observation Page which includes the ephemerides for artificial objects in orbit around Earth that have been (or could be) mistaken for natural objects. UPDATE: unfortunately this doesn't exist any more, but this page does keep track of them. You can also try Jonathan's Space Pages.
Other indeterminate objects might be too small, or too weathered, or too generic to tell anything about them except that they were once part of a spacecraft.
Of course this distinction between 'natural' and 'cultural' becomes very important in the SETI programme, as we need to tell the difference between them if we want to attribute something to sentient activity.
Dust: I've become quite obsessed with dust over the last few years. Here's one definition: 'fine, dry powder consisting of tiny particles of earth or waste matter lying on the ground or on surfaces or carried in the air'. Looking through other definitions, they share the features of dryness and transport. Dust is not necessarily undiagnostic - it should be possible to tell the difference between terrestrial, interplanetary, interstellar, and human-made. I'm interested in the human-made dust here, obviously. What are its characteristics? How could we use it analytically?
I guess here I'm looking at a micro-universe or landscape of particles which are miniplanets, moons and galaxies in their own right. Perhaps for some beings in the universe it's the dust that's the main game. Perhaps we shouldn't be out there looking for alien megastructures, but for dust clouds which seem to be artificial.
Offensive weapons: By this I don't mean personal weapons like handguns, but weapons of mass destruction, or anti-satellite weapons. Orbital weapons could be deployed against other spacecraft, space habitats or planetary surfaces. It's possible that weapons could be directed towards Earth - this is what, after all, many feared that the first satellite Sputnik 1 was going to do. The Russian Almaz military space station, launched in the 1960s, had a space gun. There are currently nuclear power sources on spacecraft, but no nuclear weapons, although there have been high-altitude nuclear tests, like Starfish Prime in the past.
So I guess we can have weapons that are nation-based or planet-based. Orbital weapons may orbit a celestial body to protect it from hostile approach from outside the planet. This could be from non-human entities or human 'nations' on Earth other planets. In one science fiction conception, it's the inner planets against the outer planets. The nature and targets of these weapons will depend on the political and social nature of populations on and off-Earth. Perhaps there will be no need of weapons in the future ....
Defensive installation: this might be a surveillance satellite or outstation, or infrastructure put into place to protect an orbital asset. There are certainly a myriad of surveillance satellites already in orbit, but most are watching Earth, not necessarily each other. Observation is always ambiguous or double-sided.
Monument or artwork: this might be passive or robotic orbital, structural, for example a ring or other kind of structure, or even made of light, shadows or dust. The viewing perspective might be terrestrial, orbital or both. It could even be intended for an out-of-solar-system audience, in the sense of being a message intended for the alien other. You could argue whether Elon Musk's red Tesla qualifies as either of these.
Gravity playground/amusement park: this is a play facility for children which is the opposite of terrestrial amusement parks - the aim will be to create heavier gravity experiences. There will be spinning things, of course, but I don't know what else, I will have to give this some thought.
The next section is about places and I'm not even really sure it belongs here at all. I was in two minds whether to call these 'space places', but they are kind of like ecological niches, and technically they exist for each planet. They are defined by gravity, magnetic fields and relationships to other space features such as moons. They're like an archaeological layer with a number of artefacts in it, the artefacts forming the assemblage. And just like on Earth, objects move between layers and confuse the stratigraphy.
Each planet and Moon will have the same range of orbits - low, medium, high, astrosynchronous. Which of them are occupied so far? We could say that Mars has Low Martian Orbit robotic orbital, and I don't know about Medium Martian Orbit. Nothing in areostationary, as we've already established. Venus has only Akatsuki in a highly elliptical orbit which ranges from 400 km above the surface to 330, 000 km. This is a sort of orbitography for each celestial body.
We might presume that there will be some vague functional equivalence; for example, planetary observation satellites will be a low orbit, telecommunications satellites will be in a geostationary orbit. But maybe there will be telecommunications megaconstellations in low orbits. It depends on the receiving technology.
Something I notice is that these orbits are all defined by their relationship to the surface of Earth, or of a planet. This says something about our planet-bound perspective. If we were looking from the outside, how would we define them?
Low Planetary Orbit (LPO) /Low Earth Orbit (LEO): On Earth this is the region between about 80 km (see McDowell 2018) and 2, 000 km above the Earth. Objects here are within the reach of the atmosphere and tend to get pulled back in. So this is a kind of orbital borderlands which includes Earth's upper atmosphere, like an intertidal zone. There are chemical exchanges between space and atmosphere. If you sampled the particles in space in this region, you would expect it to be distinct from higher orbital regions. There should be a sort of equilibrium between the 'natural' and 'cultural' components.
Let's think about this for other planets. A key defining feature is the interaction with the atmosphere, so this height and the nature of the interaction will depend on the density and extent of the atmosphere, and its interaction with solar activity. Mars and Venus have atmospheres, and of course the gas giants are just one big atmosphere. Each planet is different so the orbits will have different characteristics.
Medium Planetary Orbit (MPO) /Medium Earth Orbit (MEO): For Earth this region extends from about 2, 000 km to the geosynchronous orbits at 35, 000 km. This means it is about 15 times as broad as LEO, with a significantly greater volume. It's also a highly geomagnetically active place, as Earth's magnetic fields ares strongest here. Not every planet will have such magnetic fields though. Mars, for example, does not have a rotating core to generate strong magnetic fields, although it does have a magnetosphere. If the MPO extends between LPO and HPO (see below), then this band will be a different volume for each planet.
Stationary /synchronous orbit: For Earth this region contains geostationary (GEO) and geosynchronous orbits. At this altitude and speed, a satellite appears to hover over the same point above Earth's surface. Traditionally, Earth's telecommunications satellites are located in GEO, although this is changing with the LEO megaconstellations. For other planets, it may be the same. Mars has areostationary orbit, about 17, 000 km above the planet's surface, and due to Mars' much lumpier mass, it's not the easiest place to stay in as explained here. Each planet should have such an orbital regime and they may be the location of future habitats or space services.
High Planetary Orbit (HPO) /High Earth Orbit (HEO): these orbits are situated above the GEO band. On Earth, this is where the graveyard orbit is located, where old GEO satellites are sent to get them out of the way. At about 150, 000 km, this orbit merges into cis-lunar space. Of course if a planet has no moons then there won't be a cis-lunar space: HEO probably goes on until objects get captured by the Sun instead. Maybe High Planetary Orbits are where you hide, as you may be hard to see from the planet's surface.
Lagrange points: there are five of these in the Earth-Moon system, and as we've already seen, some have been proposed as the location of habitats, graveyards and museums. The ESA SOHO solar observatory is currently parked at L1. L4 and L5 are the location of the Kordylewski dust clouds and it's my contention that satellite dusts will end up there too. Most planets have stable L4 and L5 points in relation to the Sun. Around Jupiter and Saturn, asteroids and other small objects often end up in the L4 and L5 points. Here is a handy list of everything located at Lagrange points throughout the solar system.
Gerard O'Neill proposed that space habitats should be built at L5, and the L5 Society was founded in 1975 to promote this idea. We're a long way from it, though ....
Cislunar space: according to Jonathan McDowell, cislunar space begins about 150, 000 km from Earth, where High Earth Orbit ends. It's not the same as lunar orbit. It's the space between Earth and the Moon, on the near side. I don't think this is a place where you stay; it's more a transit space. Other planets, of course, have many moons, and many tiny ones too which don't exert as great a gravitational influence as our own one. Cislunar space may be something very complicated on other planets.
Rings: I don't know what kind of human places might be made in or near planetary rings. They might be mining installations, for example - extracting metals and ice to supply orbital or surface habitats and industries. Of course Saturn has the best-known ring system in the our solar system, but most of the outer planets have rings too (Neptune, Uranus, Jupiter). It might be that they are too dangerous for prolonged activity with a very high risk of collision with the particles and rocks that make up the rings. I need to do some more thinking about this.
Solar orbit / heliocentric orbit: well, the whole solar system is in solar orbit, but here I'm interested in artificial objects. There's a lot of lost stuff orbiting the Sun, as well as objects designed to be there, like the Parker Solar Probe. Elon Musk's red Tesla sportscar is in solar orbit, as well as objects like SW 2020, an asteroid which turned out to be an old Centaur rocket body. Habitats and factories could be in solar orbit. Perhaps one day there will be artificial planets. I wonder how you would construct an artificial planetary core.
Lost objects: for space, this encompasses two things: objects that genuinely got lost, and those with whom we lost communications, so we can't verify their location, although it can be predicted, like Pioneer 10 and 11. If we have lost objects in space, then perhaps aliens have also lost their own objects which we might find. So tracking how and what gets lost is interesting in a number of ways.
We could also classify places according to how big their population is, or how much buffering humans need to exist in a place. A city might have enough artificial atmosphere for people to live without space suits all the time. A planetary landscape might be a completely 'natural' environment, or terraformed (partially or completely).
What is separate on Earth may be bundled together in space; what contemporary capitalist populations see as 'natural' divisions of space and function may be turned inside out. Children may be separated from day-to-day life as they require special gravitational conditions to gestate and grow. Work and home might be the same space. There may be no place set aside for the dead. It's about pulling apart our assumptions about what is 'normal' (or 'nominal') life in human societies. From an archaeological/anthropological perspective, we may see many marginalised or past forms become dominant in other planetary societies, as well as completely novel forms that have never existed on Earth. In this article, I look at how gravity might structure society.
Because we evolved on the surface of Earth, most of our infrastructure is on the surface too. On other planets, it might be mostly underground or under oceans where people are not exposed to the dangers of high radiation or lethal dust storms. The surface might be left to the robots. On gas planets or those with challenging surfaces, human habitats might be aerial, in a powered low orbit or tethered in some way.
What kinds of sites that we don't have on Earth might we find on other planets? Terraforming machinery? Ice mines? Perhaps there will be a market in ice cubes from other world's water ices to put in your cocktails! What kinds of Earthly places simply won't exist in space? Well, coastal and riverine infrastructure, like jetties, wharves and bridges, which won't be needed on most planets or moons for a start .... an almost ubiquitous feature of terrestrial architecture is water management like pitched or domed roofs, gutters, drains and so forth. Not much need for that on dry planets. You might expect early space habitats to have features in common with terrestrial design because it is familiar and ingrained in how people think of these things. As time goes by, such features may gradually be abandoned and the architecture will look increasingly otherworldly to our eyes.
So here's my attempt to tackle other planetary environments.
Surface rover: in archaeological terms, a rover site consists of the actual rover vehicle, and all the tracks it makes. These will survive to varying degrees depending on the planetary environment. Rovers could be automated, or crewed, meaning that they only operate with a human driver. A crewed rover is not the same as a mobile habitat, however. So we had better define exactly what we mean by a rover. This is from Wikipedia:
A rover (or sometimes planetary rover) is a planetary surface exploration device designed to move across the solid surface on a planet or other planetary mass celestial bodies.Note that you can't have a rover on planets which have no solid surface! A rover is generally an exploration device rather than a transportation vehicle ie it is not designed to take people or goods between specific destinations. I guess a rover may not have always have a destination as it's about the journey.
Laser ranging targets: we already have some of these in Earth orbit, on the Moon and on Mars. Now I come to write this I realise it is more complex than I was thinking. So there are interplanetary laser ranging targets and sources, but there are also local ones - intraplanetary - and both range from sessile (like the Apollo 11 one), mobile (as in Perseverance and Lunokhod until it stopped working), to orbital (like my favourite LAGEOS 1 and 2 satellites). What if we were to map the distribution of laser retroreflectors throughout the solar system?
Floaters/flyers: This leads me to consider the distinction between orbiters and rovers. For a gas planet, you can of course have orbiters, but their path is predetermined by astrodynamics. I think the point of a floater or flyer is that it can respond to new information and change course: its motion is semi-autonomous and maximised for the retrieval of scientific information. So this becomes a cloud or upper atmosphere rover, if it was not actually orbiting. The opportunities for this are limited, as not every planet or moon has atmosphere or gravity which is conducive to suspension.
Landing sites: there's a few different types. They may be distinguished by function, location and system - for example, a landing site for a vehicle which connects with an orbiting vehicle may be different from an interplanetary vehicle landing site. So perhaps one way of classifying these is the origin of the vehicle - local or interplanetary. Now I realise I need to go back and make this category for Earth as well.
- Robotic planetary landing: this is an uncrewed vehicle
- Automated: this is a transfer vehicle which performs round trips
- Human/passenger planetary landing
- Industrial
- Crash landing site - either deliberate or accidental
Launch site: Already these will have to be very different to the ones we know from Earth. Mars and the Moon do not have such intense gravity to escape, so rockets can be smaller (if they are not intended for return). Both planets are very dusty so launch pads will have to be designed to minimise dust. Dual-use airfields are unlikely, as aeroplanes won't work on the Moon or Mars. Well, they just might on Mars, but you have to travel at extremely high speeds and not stop. Balloons might be a different matter, I will have to investigate further. And maybe there will helicopters.
Spaceport: a spaceport on other planets has the same function as one on Earth, but will probably be of a very different design. Depending on the planetary structure, it might not even be a solid, stationary place on the surface. A spaceport on Venus, for example, will likely be in the cloud decks rather than on the surface.
On planets with lower gravity than Earth's, elevators from the surface up to orbit may link a ground station to the spaceport - like an airport but with the inside part outside Earth. The weird sort of no-placeness of being inside airports once you've gone through security will be a much more extended geographic and chronological place.
Automated sampling site: this is where a robot lands/arrives, takes a sample, and analyses it or returns it. The site consists of the pit or trench where material has been removed and any robot or spacecraft components which remain behind. Exploration drilling would be included here, as well as scientific drilling.
Astronaut sampling site: where humans have taken samples, such as the trenches and cores associated with the Apollo crewed missions to the Moon.
Automated sampling site: this is where a robot lands/arrives, takes a sample, and analyses it or returns it. The site consists of the pit or trench where material has been removed and any robot or spacecraft components which remain behind. Exploration drilling would be included here, as well as scientific drilling.
Astronaut sampling site: where humans have taken samples, such as the trenches and cores associated with the Apollo crewed missions to the Moon.
Rock art site: rock art is among some of the earliest archaeological remains on Earth, and I wonder if future inhabitants of other celestial bodies would also make use of the landscape to make marks. There is a story that Apollo 17 astronaut Gene Cernan left graffiti on a Moon rock. Wikipedia debunks this:
A popular belief is that Cernan wrote his daughter's initials on a rock on the Moon, Tracy's Rock. The story, and Cernan's relationship with his daughter, was later adapted into "Tracy's Song" by pop-rock band No More Kings. The story is inaccurate, as Cernan wrote her initials in the dust, not on a rock. He states in the 2014 documentary The Last Man on the Moon that he wrote them in the lunar dust as he left the rover to return to the LEM and Earth.[41]
So not rock art as such, but I'd argue it still counts. Maybe we make a new category for regolith art. The question is how long would such a trace last. It might might have been blasted away as the ascent module took off; if not, then bombardment from micrometeorites might eventually erase the initials. Lunar dust expert Brian O'Brien calculated that Tracy's initials would last 28, 000 years.
There are rocks on Venus, Mars, the Moon and numerous other Moons and asteroids throughout the solar system. Space rock art may take different forms according to the technology: a laser cutter would produce very distinct engravings, for example. The art is equivalent to that scratched in rocks by sailors at landfalls across the world.
Residential: this is where people live. It might be military, civil, or commercial - effectively, a company town. It could be a city, town, village, or an isolated residence. Towns may contain the full range of building types or functions that we expect on Earth, for example:
- Civic - eg town hall, court
- Entertainment - sports ground, music venue
- Hospitality - restaurant, cafeteria, bar
- Waste management plant
- Water treatment and storage
- Food production - agricultural, processing, packaging, distribution
- Worship - church
- Hospital/medical
- Childcare
- Power infrastructure - solar, electrical, geothermal, wind, hydro
- Transport infrastructure - trains, rockets, cable/mast, tunnels, rail, balloons
- Launch/landing pads
- Gravity simulation sites
- Scientific - observatories, radiotelescopes, field laboratories and research stations
- Telecommunications: satellites, cables, radio
- Playgrounds, parks
Equally, urban design is likely to be completely different to anything we know on Earth. Proxemics, the science of social distance, will have manifestations as diverse as there are people. Martian settlements may look like saints on the pillars in the Turkish desert.
A residential site might be stationary or mobile, like a city of lunar rovers.
Industrial: planetary industrial sites could include mining sites, manufacturing facilities, processing facilities (eg oxygen and water), treatment facilities, industrial waste disposal. What do oxygen manufacturing facilities look like on Earth? There might also be storage of materials or supplies. Manufacturing might be for objects for local use, or for trade off-planet. These are likely to be machine landscapes.
Biosphere: this could be a habitat for humans, or where plants and animals are grown or farmed to supply a human population. It is a sealed structure which aims to reproduce the conditions under which a species can survive, replicating perhaps seasons, temperatures, humidity, light, water, soil etc from a world of origin. Effectively, a biosphere is an artificially constructed terrestrial analogue landscape - just like a terrarium I guess!
Arcology: an arcology is an architectural structure with a high-density population and low ecological impact. Generally, they are self-sustaining, containing within them all the necessary agriculture and industry needed for the population to survive. It's far more than just a sky-scraper. Arcologies have been a feature of science fiction for a long time. One of the first appeared in the classic Nightland, by William Hope Hodgson, in 1912. Basically, the inhabitants of the arcology need never go outside. The City in the Arthur C. Clarke's The City and the Stars is also such an enclosed environment, but the population is low, so it might not count as an arcology. In the series Silo, based on the novels of Hugh Howey, the arcologies are underground. On other planets, arcologies could reduce the impact of human activities on the natural environment.
Terrestrial analogue landscapes: places on other planets which resemble Earth. I don't know if there are any! I suppose you could take the places on other planets which most resemble analogue landscapes on Earth. You might also argue that an Earth analogue on another planet has a particular sort of natural and cultural value. Perhaps domestic tourists on places like Mars would go on holidays to locations which resembled Earth. This might be for a range of reasons - similar geological formations or landforms; similar mineral composition; similar colours; temperature, resemblance to a time of day ie it might only be an analogue in certain conditions of light and shade - what else? Is there any other planet or moon which has a blue sky? Let's face it, most of these will be more like deserts or the Antarctic. So really this is about mapping the degree of similarity between landscapes across the solar system. You'd have to work out what are the key features that they have in common. I hope someone has done this research!
Multi-segment sites: these are organised around nodes. So far we have user and ground segments on Earth, connected to space segments in orbit, and on the Moon, Mars and a few other places. At some point, there may be ground segments on the Moon and Mars as well. A telecommunications satellite in Earth orbit might have users on Mars or the Moon.
Transport infrastructure: roads, rail, aerial, subways. It's likely that humans will not travel as much as robots and goods. There'll likely be intraplanetary and interplanetary transport infrastructure.
Defensive, interplanetary and intraplanetary: defensive structure meant to protect against assault from space-based weapons, maybe in the event of war with another planet or Moon, or to protect a place against domestic assault.
Whole planet habitat: this is more likely to be an asteroid. Of course you could say Earth is a whole planet habitat right now; but here I'm thinking more of a planet, planetoid or asteroid that contains cavities in the interior for people to live, rather than living on the surface. The body of the planet is used as an architectural material. The body might function as a spaceship with its own propulsion, or it might be a mining site and residential are rolled into one.
Terraforming facility: an installation producing gases or doing something to terraform a planet or Moon.
Deep time repositories: these already exist, and there are plans for more. The idea is that information, data, art and DNA can be sent to the Moon to ensure its survival if there is catastrophe on Earth. The data is stored digitally on high-density media such as nickel discs.
Deep space probes: these are among the few deep space sites we have at the moment. The Voyager, Pioneer, and New Horizons spacecraft are all out beyond Jupiter and, in the case of the Voyagers, even beyond our solar system. In the future, I imagine there will be many more probes or observation satellites in the outer reaches of the solar system.
Residential: will people live in deep space? It's cold and dark, and so far from the energy-giving warmth of the Sun. In Charles Stross' novel Accelerando, AI lobsters force people out beyond the inner planets where they live in deep space habitats. Or something like that, it is a while since I've read this novel. Other science fiction writers have also imagined people living far from the Sun in deep space.
Industrial: I'm not sure what resources there are in the outer reaches of the solar system for sustaining local economies. There might be factories and storage facilities for fuel, water and oxygen gathered from comets, asteroids and the interplanetary medium. Nuclear power might be more common than solar power.
Gas giant mining: this is infrastructure for extracting hydrogen, helium and other gases from Saturn, Jupiter, Uranus and Neptune as fuel for terrestrial or outer planet economies. This will be a multi-component set of spacecraft and facilities, most likely to be automated with no human presence. It may consist of atmospheric exploration vehicles, GPS satellites, weather observation satellites, gas scoop vehicles, shuttles to transport the cryogenic gases, storage facilities on local moons, and shuttles to Earth or other markets. Uranus and Neptune are best locations for this industry as they 'require lower energies
needed to attain orbit and present less danger from powerful atmospheric lightning' (Palaszewski 2015:2).
Spaceport: a free-floating launch stage for moving around the solar system, and outside it into interstellar space. Perhaps this is a staging post for generation ships or ships venturing beyond the heliopause.
Deep time repositories: storage of data, genetic material, artefacts. These are designed to be resilient against 'existential risk'. They may also be time capsules. They could be individual, national or curated by an organisation. We already have one example, the Voyager Golden Records.
I'm not really sure what kinds of sites scale up to galactic level. They might be massive stellar engineering projects, something like the Douglas-Ouyang planets. Perhaps Dyson Spheres and Matrioshka Brains, taking up an entire solar system, count as galactic sites. Of course here I'm thinking of what humans might create, but that's either in the most far, furthest future than we can imagine, or in another group of being's far, furthest future. Maybe this galactic-level structure isn't even made by sentient beings. It might be spacefaring microbes or unthinking algorithms. AIs or robots might be the creators. We must of course turn to science fiction writers for our knowledge of what this kind of future may hold.
Final thoughts
Of course, I'm coming at this from an archaeological perspective. I'm interested in the archaeological record that such sites would leave in the universe. Another angle is what we could learn from this to identify the remains of extraterrestrial sites in other solar systems. If we consider the range of solar system niches that would exist, no matter how different from our own, we can start to narrow down the places and nature of the material record we might expect to find there.
We must take into account the evolutionary trajectory of some sites into others. So the origins of the deep space habitats might be the Earth-orbiting habitats; the origins of a Martian city might be a Martian research outpost. For the archaeologists, this is thinking Harold Dibble-style about Middle Palaeolithic scrapers. What appear to be final 'types' are in fact the same artefact at a different stage of use and/or retouch.
If I had made this a systematic study, drawing on the multitude of insightful science fiction explorations of off-world and future space installations and habitats, it would be far more extensive than this, and no doubt more useful too! I'm still keen on the idea of making this into a huge table which would reveal the gaps but this can be for another day. To be honest I've been tinkering at this post for the better part of Covid Year 2 and half of Covid Year 3 so it's time to put it out there.
UPDATE: OK it's 2025 'Covid is not over' and I still hadn't finished this post! I've gone through, edited and added slightly, and checked all the links. Here it is for your delectation.
References
Augé, Marc 1992 Non-Places: An Introduction to Anthropology of Supermodernity, Le Seuil: Verso
Dorrington, Scott and Olsen 2019 A location-routing problem for the design of an asteroid supply chain network. Acta Astronautica 157:350-373
Eriksen, C., 2020. Artificial Gravity in Popular Culture. In Outer Space and Popular Culture (pp. 57-62). Springer, Cham.
Gorman, A.C. 2019 Dr Space Junk vs the Universe: Archaeology and the Future. MIT Press
Gorman, A.C. 2018 Gravity's playground: dreams of spaceflight and the rocket park in Australian culture. In Darran Jordan and Rocco Bosco, eds. Defining the Fringe of Contemporary Australian Archaeology. Pyramidiots, Paranoia and the Paranormal. Newcastle upon Tyne: Cambridge Scholars Publishing, pp. 92-107.
McDowell, Jonathan C. 2018 The edge of space: Revisiting the Karman Line. Acta Astronautica 151: 668-677
Palaszewski, Bryan 2015 Atmospheric Mining in the Outer Solar System:
Resource Capturing, Exploration, and Exploitation. NASA/TM—2015-218096
Scharmen, F. 2019 Space Settlements. New York: Columbia University Press
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