Our current speculative discourse on the colonisation of other planets tends to consider future buildings through the lens of hitech architecture. However, we suggest that developments in biotechnology will enable types of construction which are beyond even our current science fictions. The paper presents an argument for bioengineered building materials framed by the notion of constructing buildings on Mars. It introduces the concept of biomineralisation and its processes and applications, and focuses on the creation of calcium carbonate by certain strains of bacteria. We will suggest that by utilising this process in conjunction with synthetic biology (where bacteria are engineered to survive and respond to the environment on other planets) a building process emerges where the materials are adaptive and, to some extent, self-constructed in relation to their environments. The paper concludes by speculating about a building process involving the use of bioengineered bacteria to consolidate materials, found on the surface of Mars, to create materials and structures which are functionally graded.