The Worldhouse

Maintaining an Ecosystem under Critical Factor Constraint: The Worldhouse

Taylor (1998) presents a best-worst-case scenerio in which the possibility of human habitation of Mars is prohibited by the critical factor of the Martian nitrogen budget (more than 85% of the original inventory may have been lost). Under such a constraint, he argues, Mars may still be made habitable by the construction of a quasi-global “worldhouse,” consisting of a 1-3 km high “roof” spanning the equatorial- and mid-latitudes. The technology required for construction and maintenance of such a structure would not necessarily be far in advance of that currently available. The author goes into detail about everything from ethanal-based fuels to meteor strike prevention, underscoring the necessity of careful planning in an endeavor of this scale.

The worldhouse would be a fundamentally different habitat than a traditional enclosed biosphere. Its sheer size, particularly in zonal extent (12,500 km), would allow for seasonal and diurnal temperature gradients and changes, and therefore weather. Such a system is almost certainly necessary for any kind of large-scale climatic and biological self-regulation. However, the lack of any volcanism on Mars prevents the recycling of CO₂ (ie. the Carbon Cycle) or other gases, so it is unlikely that the worldhouse environment would ever be absolutely self-sustaining. A degree of periodic geochemical intervention would be necessary to prevent long-term deviations from environmental equilibrium.

The table below gives the atmospheric mass savings of Taylor’s “paraterraforming” alternative. Given the likely insurmountable difficulty of full “open-skies habitability” on Mars, it is not so hard to see such a solution as a viable way around full terraformation.

Required Atmospheric Masses

1 bar Atmosphere	Atm. Mass: % Terrestrial	Atm. Mass: Units of 10¹⁸ kg
Earth	100	5.28
Mars Terraformed	74.24	3.92
Mars Worldhouse:
Paraterraformed 3 km	9.85	0.52
Paraterraformed 2 km	6.63	0.35
Paraterraformed 1 km	3.41	0.18