The tree · Drive · Happens to the world · Plays out over the whole window
A crew lands on Mars and returns to Earth
The transit-in-months milestone with people aboard: the first round trip proves that a crew can be carried across the inner solar system and back, which is what working rotations to an outer site require. It needs the launch, propellant, and life-support nodes as much as the drive, and it is placed under drive because the transit is the hard part it resolves.
The test: what counts as it having happened
People land on the surface of Mars and return alive to Earth, confirmed by the responsible agency or company and independent tracking of the vehicles.
Settled by: The responsible agency's or company's mission record and independent tracking
Replaced
Replaced by A crew travels beyond the Earth-Moon system and returns to Earth.
The odds, by how long I live
| baselineto 2071 ± 8 | moderateto 2080 | strongto 2095 | radicalto 2136 | openno deadline |
|---|---|---|---|---|
| 45% | 60% | 78% | 90% | 93% |
Each column is a different guess at how long I live, from current trends (baseline) to open-ended. The number is the chance this happens before that deadline, assuming everything it depends on happens first. As of September 19th, 2026.
Why these numbers: One company is building for it, and refilling in orbit is one link of a long chain: crew-scale landing, surface systems, ascent, return propulsion, multi-year reliability and a programme willing to accept the risk all remain. Under even odds by 2071; likely by 2095 if the launch architecture works at all.
What the ledger says about this step
- A crew landing on Mars and coming home came down: refilling in orbit is one link of a long chain 2026-09-20 Changed my mind
The last check
Once a week the tree is read against the news, node by node, against the test above. Open a line to see what that week held. Every check ever made on this node is on the Radar page.
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2026-09-19 Nothing new
No new developments appeared in the window; SpaceX's announcement pushing a crewed Mars mission to roughly 2031 to 2033 dates to February 2026, before this window, and NASA and SpaceX focus remains on lunar Artemis missions.
Revisions
| Date | Field | From | To | Why |
|---|---|---|---|---|
| 2026-09-19 | probability | 0.55 / 0.70 / 0.85 / 0.93 / 0.95 | 0.45 / 0.60 / 0.78 / 0.90 / 0.93 | Step 27 outside-model review, item 71 (docs/reviews/2026-09-19-rulings.md): the first rationale leaned on one company's plans and the only dependency granted is the propellant transfer; moved partway toward the reviewer. Decided September 19th, 2026. |
| 2026-09-25 | status | open | superseded by D-crew-round-trip-beyond-the-earth-moon-system | Candidate 5 of docs/proposal-function-over-route-2026-09-25.md, I approved September 25th, 2026: what the beyond-the-Moon site takes from this step is a crew that has gone beyond the Earth-Moon system and come back, and Mars is the likeliest instance rather than the requirement. This node's numbers were published, so it is retired and replaced rather than renamed (docs/methodology.md, 'What is fixed and what moves'). |
Notes
Edge drawn at step 7 (September 8th, 2026): a Mars departure on any current architecture needs refilling in orbit. Life support and shielding make it safer, not possible, so they are not hard dependencies. Step 27, item 76 (September 19th, 2026, declined): this node stays the only dependency of the beyond-the-Moon site node, standing in for 'a crew has gone beyond the Moon and returned'; it would be widened rather than removed if another destination came first.
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what happens next.
The record itself is data/D-drive.toml in the public repository.