Earth has, officially, two hundred years of resources left. The Allocation Authority rations water, air, and power. The dust gets into lungs. On Europa, Jupiter's ice moon, there is an ocean and a future, and a war: the Solar Marines hold the colony against breakaway human Free Settlers and against the Vey, an intelligence that lives beneath the ice. The Corps raises children born into its care in the crèches, and it pays their families on Earth for them. That arrangement is called the Covenant.
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A child needs a birth license, and the local quotas have been closed for years. A registered household may keep a declared, unlicensed child without an allocation of its own, sharing its parents' rations until the quota reopens. A person with no household registered before the conception cannot. An undeclared pregnancy is taken into the Covenant, and the mother is sent to a labor unit.
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Covenant infants travel to Europa sedated, in the cold holds of the supply ships: an eleven-month crossing. Troop ships make it in about four. Officially, crèche children begin compulsory service at sixteen. In practice, they rotate through the perimeter from age twelve, and the Corps records it as instruction.