Every object humanity has placed on, or crashed into, another body carried microbial life. The international regime that governs this — planetary protection (PP), administered through COSPAR — has changed shape repeatedly since 1964, and a mission is bound only by the policy in force at its launch. This note derives, deterministically and per mission, three things from public catalogue fields alone: the mission's physical-contact class, its COSPAR target category under both the contemporary and the present-day policy, and a modelled upper bound on the viable bioburden it could have delivered while fully satisfying the rules of its day. Nothing here is a compliance verdict; the regime is reconstructed, not judged.
Each landed or impacting object in the registry already carries, from
the General Catalog of Artificial Space Objects (GCAT, J. McDowell), a
lander-type byte (LType), an end-state byte
(Status), a target world, and a launch date. These are RAW.
The derivation adds PROCESSED fields; no parameter is invented.
Mission class maps LType to one of
impactor / lander / orbiter / probe / rover / ascent-return / human /
stage / component. Physical contact maps the
Status byte (failed → none, flyby → none, en-route,
reached-surface, returned) to the body. COSPAR category
is then a table lookup over (world × class × contact):
| Category | Meaning | Bodies (forward) |
|---|---|---|
| I | no protection — body of no biological interest | Mercury, Io, gas-giant interiors |
| II | documentation/reporting only — no bioburden limit | Moon, Venus, the giant planets |
| III | orbiter of an Icy World / a restricted body (probability-governed) | Europa, Enceladus, Ganymede, Callisto, Titan, Ceres |
| IV (IVa/b/c) | surface mission — Mars (IVa/b/c) and Icy-World landers (≤30 spores) | Mars; Icy-World surfaces |
| Vu / Vr | Earth-return, unrestricted / restricted | Moon, Venus (Vu) · Mars, Icy Worlds (Vr) |
This reflects the 2024 COSPAR restructure (published Space Research Today n°224, Jan 2026), which defined a formal Icy Worlds class (outermost layer predominantly water ice) defaulting to Category III and reclassified Ceres, Ganymede, Callisto and Titan into it; Mercury is Category I. Phobos and Deimos are not formally categorised — they are treated here conservatively as Category III (potential Mars-ejecta transfer).
A mission is bound by the regime in force when it flew. The timeline resolves to three epochs, each with its governing instrument:
| Epoch | Years | Governing instrument |
|---|---|---|
| pre-policy | < 1964 | no international policy (NASA internal provisions from 1963) |
| probabilistic era | 1964–1983 | COSPAR Resolution 26 (1964); Outer Space Treaty Art. IX (1967); Sagan–Coleman probabilistic budget (1965) |
| category system | ≥ 1984 | COSPAR target-category system I–V (adopted 1984; Cat IVc added 2002; rev. 2008/2011/2020-21/2024); NASA NPR 8020.12 |
The contemporary category is the present-day category once the I–V system exists, and an era label before it; the present-day category is always computed, so the two can be read side by side — what a mission would incur today versus what governed it then.
The categories hide a governance fact: for most bodies, compliance imposes no limit on delivered life. Category I and II compliance is documentation/reporting only — no spore cap — so a mission can meet every rule and still carry its full microbial load, unbounded by policy. Among the categories any mission in this catalogue incurs, only Category IV bounds the COUNT of delivered spores (IVa: ≤ 3×105 total and ≤ 300 spores/m²; IVb/IVc: ≤ 30 total, Viking terminal sterilization). Category III bounds a contamination probability (body-dependent, e.g. < 10−4 for an Icy-World ocean), not a count; Category V restricted requires containment of returned material, not a forward-spore cap.
| Regime (category) | Spore cap on a compliant mission |
|---|---|
| Cat I / II / pre-policy | none — unbounded by policy (documentation/reporting only) |
| Cat IVa (Mars lander) | ≤ 3×105 spores total, ≤ 300/m² (Viking-derived) |
| Cat IVb / IVc · Icy-World surface | ≤ 30 spores total (Viking terminal sterilization) |
| Cat III (orbiter) | a contamination-probability budget, not a spore count |
The 300 spores/m² is the Cat IVa regulatory ceiling (Viking- derived), not a cleanroom-delivered figure — a measured ISO-8 spacecraft surface runs ~35 spores/m². For the uncapped Cat I/II case the registry records "no cap", never an invented number; a Factory model (deriveBioburden, MODELLED) supplies only an order-of-magnitude reference for a controlled craft (≈ the Viking-assembled ~3×105 total), with the inputs (class, world, epoch) RAW/PROCESSED.
Counting, per body, how many contacting objects fell under an uncapped regime versus a capped one is a measure of the regime, not of any actor. Its interest is that a body can carry a large, entirely uncapped record: the Moon has received many Category II landings, each subject to documentation but no spore cap — so policy bounds the biological burden it could have received at nothing — whereas every Mars surface contact falls under Category IV, the one regime that binds a number. That asymmetry is the governance signal: it shows where the present regime constrains humanity's biological footprint and where, by design, it does not — informing, without overclaiming, the contextual awareness the registry exists to provide.
Run over the full GCAT lander catalogue (421 objects that reached a body), the metric is policy-exact — no modelled density enters (pp-rollup.json):
| Body | Contacts | Uncapped | Capped (Cat IV) | Σ permitted caps |
|---|---|---|---|---|
| Moon | 224 | 224 | 0 | — |
| Mars | 93 | 0 | 93 | ≤ 2.8×107 |
| Venus | 59 | 59 | 0 | — |
| Titan | 8 | 0 | 8 | ≤ 240 |
The Moon's 224 contacts are every one uncapped (Category II / Vu — compliance is documentation only), so policy places no ceiling on the biological burden they could carry; every one of Mars's surface contacts falls under Category IV, which caps each at ≤ 3×105 spores. The contrast is the kind of bound — uncapped versus capped — not a spore multiple. Every figure here is policy-exact (contact class, category, the uncapped/capped counts, the summed numeric caps); the model invents no density. (These per-object classifications are DERIVED; they reproduce the curated worked sample but are not themselves reviewed.)
A scholarly survey of the planetary-protection literature (COSPAR policy; NASA NPR/NID; National Academies / NRC; the MEPAG Special-Regions analyses; Coleman–Sagan; the 2019 Planetary Protection Independent Review Board) identifies classification dimensions a registry can carry beyond the single COSPAR target category. The registry derives the cheaply computable ones directly:
| Axis | Values | Derived from |
|---|---|---|
| contamination direction | forward · forward+back | mission class / return |
| Earth-return class | Vu unrestricted · Vr restricted | body × return |
| requirement regime | unmitigated · Cat IV cap · probability-governed | category × epoch |
| compliance-uncapped | does the rule cap delivered spores at all? | the requirement regime |
| intrinsic habitability | none · low · special-region · icy-world | per-body (cited) |
| recategorisation history | the dated events that changed a body's protection | per-body timeline (cited) |
A body's category is the conjunction of its intrinsic astrobiological potential and the mission's interaction with it — the two-factor structure the literature makes explicit. Each body's protection has its own history: the Moon was placed in Category I/II (with protected polar/heritage zones, and a 2021 IIa/IIb refinement for lunar landers) by NASA's 2020 NID 8715.128; Mars's Special-Region survival temperature was reviewed at the 2007 COSPAR colloquium; the icy bodies were adopted in 2011; Ceres, Ganymede, Callisto and Titan were classified as Icy Worlds in the 2024 COSPAR restructure. Reading a mission against the timeline at its launch is what makes the classification historical. The Mars Special-Region thresholds are the SR-SAG2 (2014) values, −18 °C and water activity 0.60 — superseding the earlier figures (SR-SAG1 2006: −15/−20 °C, aw 0.5–0.62; the 2007 colloquium recommended −25 °C); the Icy-World bound is a contamination probability below 10−4 per mission over a 1000-year horizon. Frontier axes the survey flags but the registry does not yet assert (impact-energy dispersal, RTG payloads, the period-of-biological-exploration time bound, and the PPIRB's proposed risk-based variable categorisation) are noted as not-current-policy.
The metric is the presence of a policy cap, not a modelled burden: where a regime caps a spore count (Category IV) the cap is the published number; where it does not (Category I/II) the record reads "uncapped", never an invented density. A Factory reference figure for a controlled craft (≈ the Viking-assembled 3×105 total) is illustrative only — measured spacecraft surfaces run ~35–300 spores/m², and a truly uncontrolled craft is not catalogued. Viability decay after delivery (vacuum, radiation, thermal cycling) is not modelled. The probabilistic-era requirement is reconstructed as a regime label, not a re-derived Sagan–Coleman probability budget per mission. The hard epistemic rule throughout: undocumented ≠ non-compliant, and the layer never asserts that a mission was compliant either — it states only the maximal burden a mission could carry without exceeding the limit then in force; it derives category and contact, never a verdict. Curated per-mission refinements (e.g. a probe destroyed in descent vs one that reached the surface) are cited data-as-code and override the baseline where the catalogue fields cannot distinguish the case.
The derivation engine and constants ship in the registry
(pp facet) and the factory (bioburden model). The worked,
reviewed sample currently attaches to real GCAT nodes; the full
reconciliation across the lander catalogue is staged. Explore the facet
with pp:contact-surface, pp:cat-IVa,
pp:doc-undocumented in the
simulation.
COSPAR Resolution 26 (1964); Outer Space Treaty, Article IX (1967); C. Sagan & S. Coleman, "Spacecraft sterilization standards and contamination of Mars" (1965); the COSPAR target-category system (adopted 1984; Cat IVc 2002; rev. 2008/2011/2020-21/2024, restructured into Icy Worlds 2024, Space Research Today n°224, Jan 2026); Rummel et al., SR-SAG2, Astrobiology (2014); NASA NID 8715.128 (2020); NASA NPR 8020.12 / 8715.24; National Academies / NRC PP reports; the Viking sterilization record. The object catalogue is GCAT (J. McDowell, public, CC BY).
Method and derived data layer © Adrien Normier, under SSR-GPL v2.0 (public-interest use free, attribution “SolarSystemRegistry.org — Adrien Normier”). Cite this page and SolarSystemRegistry.org.