Zygote (and later Gamete) was the secret underground city that was the home of Hiroko Ai's group and a major city of the Martian underground.
Zygote was situated very near the south pole of Mars, inside a large natural cavity under the dry ice (solid carbon dioxide) of the polar cap. The dry ice was sprayed with water, which froze and formed a solid dome under which the settlement was protected and airtight.
More than a city, the Zygote dome was large enough to sustain an entire ecosystem: a mesocosm. The one kilometer tall dome sheltered a central lake, housing, farms and vegetation such as pine trees. The lake had a system for generating artificial waves, which prevented the water from freezing and was in effect an artificial weather machine: it created temperature differentials, mists, fogs, winds, rain, snow. Because of the higher temperature inside, maintenance on the dome, whose water ice was melting, was performed often. The dome gave the Zygote sky a faint white and shed diffuse light.
The settlement itself, a village on the hills, consisted of a number of houses painted white and blue and big bamboo treehouses. Everything was made out of locally grown bamboo. The treehouses, four or five steps in diameter, were hollow vertical cylinders in which many rooms and stories could be created. There were dorms, a schoolhouse and a bathhouse. Power was drawn from a Rickover nuclear power plant.
Zygote was accessed through a kilometer-long tunnel in the dry ice and a series of locks. The entrance of the tunnel was at the base of an ice cliff. The entrance and Zygote itself could not be seen from space, and Zygote made its best efforts to reduce heat that would make them visible from above.
Zygote was established in ca.2033 with the arrival of the Areophany group, the group of followers of Hiroko Ai. The Areophany group had moved out of Underhill in ca.2031 and spent the two following years turning the Zygote location into a viable settlement, operating out of a temporary hideout at Dolmen Tor, an underground sequence of caves at Aureum Chaos.
Zygote was the only city anywhere near the south pole at that time, and it successfully kept its location secret from the larger public for over seventy years.
In the aftermath of the First Martian Revolution of 2061, Zygote welcomed many members of the First Hundred who were brought there by Kasei and Michel Duval. The south polar region became the stronghold of the Martian underground. Many settlements were created in proximity of Zygote and Zygote became the geographical and, thanks to Hiroko, the moral center of the underground. The settlement produced scientific instrumentation for the underground.
Zygote also was the site of in vitro experiments of the Areophany group. In Zygote, the technique to produce ectogene children was perfected. In ca.2077, a whole series of ectogenes were born, among them Nirgal and Dao. They were brought up inside Zygote and tought by such illustrious professors such as Hiroko, The Coyote, Maya Toitovna, Nadia Cherneshevsky and Sax Russell.
In the 2080s the permanent population of Zygote was 124 people, although at any time about 200 were living in it and could be sustained with the local food production. Zygote would provide shelter for other underground groups whose dome ecosystem would collapse and thus, despite greenhouse farms extensions and new housing, Zygote began producing less than was needed.
In ca.2091, Zygote had its first death and funeral with Simon Frazier.
In the 2090s, the above zero inside temperature and the rising temperature outside, because of terraforming, made the dome unsustainable. One day a great part of the ice dome collapsed beyond repair. Steam hoses were used to melt an entirely new cavity, 300 meters below the ice. The entire Zygote was relocated, from the buildings to the sand and biomass. The new Zygote was named Gamete.
Gamete took part in the Dorsa Brevia Conference of the underground in 2107.
When the UNTA/metanational troops began to systematically destroy the underground settlements of the south polar region in the 2110s, Gamete sheltered as many as was possible. Eventually, Gamete itself was found and destroyed. Its population was relocated to Dorsa Brevia.