This is for a setting I'm creating based on a far future, terraformed, post-apocalyptic Mars. My objective is to build an epic fantasy world out of hard science fiction parts, to bring the 'feeling' of fantasy into the realm of the possible. And that requires rigorous attention to detail.
Now the thing about Mars is that it doesn't have any fossil fuels to cheaply power an industrial revolution, explaining the classic fantasy trope of "pre-industrial stasis". I was expecting that going in, and I think I've made a decent enough job of untangling the Industrial Revolution innovations that require fossil fuels from those that do not (but I could always do with some more pointers on this).
But for the same reason it doesn't have fossil fuels, Mars also doesn't have large amounts of limestone. While there is some that resulted from chemical reactions in drying lakebeds, those meagre deposits are now at the bottom of refilled lake and seabeds.
The only other way to get Calcium Carbonate is by farming snails and oysters for their shells, and recycling the eggshells of birds. That's enough for small scale uses, but using it for construction doesn't seem economically viable.
No limestone means no mortar, cement, concrete, or any serious mineral adhesive. All you've got is mud and plaster, or just no mortar at all.
My problem when researching this is that lime-based mortar seems to be such a basic invention that its use often goes unremarked. I'm sure there are certain architectural designs that have lime mortar as a hard requirement, like the flying buttresses of medieval cathedrals. I'm sure there are many features that typically use mortar, but can be achieved without it. Dry stone arches are certainly possible, or else all those pictures on google images are liars, but what are their limits compared to mortared arches? When studying Bronze Age architecture for examples, should I be worried that some of their elements are the result of factors other than the absence of good mortar?
Any insight on this issue would be greatly appreciated.
Hi there - we're happy to approve your question related to your fantasy setting, and we are happy for people to answer. However, we should warn you that many flairs have become reluctant to answer questions for aspiring novelists, based on past experience: some aspiring novelists have a tendency to try to pump historians for trivia while ignoring the bigger points they were making, while others have a tendency to argue with historians when the historical reality does not line up with what's needed for a particular scene or characterization. Please respect the answers of people who have generously given you their time, even if it's not always what you want to hear.
Additionally, as amazing as our flair panel is, we should also point out that /r/AskHistorians is not a professional historical consultation service. If you're asking a question here because you need vital research for a future commercial product such as a historical novel, you may be better off engaging a historical consultant at a fair hourly rate to answer these questions for you. We don't know what the going rate for consultancy work would be in your locality, but it may be worth looking into that if you have in-depth or highly plot-reliant questions for this project. Some /r/AskHistorians flairs could be receptive to working as a consultant in this way. However, if you wish for a flair here to do this work for you, you will need to organize this with them yourselves.