Driving through the dusty town of Hesperia, in California's Mohave desert, the eye gets lazy. If you discount the rolling backdrop of the Sna Bernadino mountains, there's nothing but mile upon mile of scrub and endless rows of cream-coloured, flat-roofed track housing. So it comes as something of a jolt when you turn a corner and stumble across Cal-Earth Institute. Suddenly, like a blip on an ECG, an array of strange, organic-shaped pods punctuate the stark horizon.
        The pods turn out to be mud-brick houses built by Iranian architect Nader Khalili, using a method he terms "superadobe". They squat in small clusters among the Joshua trees dotting the institute's seven-and-a-half-acre site. These mud huts - and their strength, durability and modular stacking properties - are the subject of considerable practical interest at the moment. The city fathers of Hesperia have just deemed themselves worthy of forming the world's first lunar colony.
        Khalili is delighted. He has waited for this moment since 1984, when he demonstrated the merits of "earth architecture" at a Nasa symposium to discuss lunar bases for the 21st century. While everyone else waxed fantastical about weird new alloys, super-malleable plastics ant the latest carbon-fibre technologies, this small intense man extolled the virtues of soil. It was an architectural back-to-basics philosophy that captured the imaginations of the space scientists.
        Though Khalili would like nothing better than to build the colony from regolith-the hard, powdery substance that covers the lunar surface- he is content for now to experiment with the rocky soil of the Mohave. In fact, the Mohave is about as close as you can get to the moon without leaving Earth. It experiences the same wild fluctuations in temperature, hot by day and freezing by night, and it is dry as hell.
        But the parallel that most interests Khalili is the similar scarcity of materials. "The most distinctive feature of this architecture is that it uses nothing but the ground under your feet," he explains, "so there is no need for the expensive transportation of materials to the moon." Beside each superadobe hut is a hole in the ground, a crude relief impression of the excavated building.
        Superadobe is essentially a technique of piling up sandbags filled with earth to form walls and laying barbed wire between them for reinforcement. It is cheap (Mars I, the most complete of the Cal-Earth prototypes, costs $270 - about 170 pounds), environmentally friendly and remark-ably strong. When Hesperia city council ran independent tests on the structures in advance of commissioning Khalili to build their local nature museum, they found that a single hut, girded with cables and tied to hydraulic jacks, could withstand the pull of 27,000lb, equivalent to the force exerted by a truck full of concrete dangling off a cliff.
        Khalili founded the Cal-Earth Institute in 1991 to promote the building of safe, affordable housing. Khalili and his British assistant Iliona Outram (the daughter of architect John Outram) now teach superadobe techniques to students from around the globe. Chances are that visitors looking for Khalili, now in his sixties, will find

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