The tree · Biology · World event · Leaf: could resolve within 1 to 5 years
A mammal is conceived, born, and weaned in partial gravity
Whether pregnancy and early development work in less than Earth's gravity is the biggest open question in off-Earth biology and has never been tested end to end. Mice have flown in a spinning enclosure on the space station that produces lunar or Martian gravity, so the experiment is within reach. A live, weaned litter is the first evidence that a settlement, rather than a work camp, is biologically possible.
What counts as it having happened
A peer-reviewed publication reports that a mammal was conceived, carried to term, born, and weaned entirely at a sustained gravity level between one-sixth and one-half of Earth's, whether in a centrifuge in orbit or on the Moon or Mars, with offspring surviving to weaning.
Settled by: The peer-reviewed publication and the space agency's mission record
Probability, by longevity scenario
| baseline2071 ± 8 | moderate2080 | strong2095 | radical2136 | openno deadline |
|---|---|---|---|---|
| 80% | 82% | 85% | 92% | 95% |
Each number is the chance this resolves yes before that scenario's window closes, given that everything it depends on resolves first. Estimated 2026-09-08.
Why these numbers: The centrifuge hardware exists and the experiment is cheap next to everything else in the tree; the risk is that partial-gravity gestation fails biologically, which would resolve the node no, not that nobody tries.
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The record itself is data/B-biology.toml in the public repository.