Planetary protection¶

Summary. Planetary protection policies "guide missions to control contamination of exploration destinations with material from Earth and prevent the potential for adverse consequences when returning material from exploration destinations back to Earth" (planetary protection white paper, p. 1). NASA's practice was built for robotic spacecraft, which can be cleaned before launch. Crews cannot: "humans on the Martian surface represent a continuous contamination source" (p. 2). The ACR25 white paper sets out what this means for the design of a crewed Mars architecture, from suits and waste to sample return. In the architecture's own lists, planetary protection is one Mars technology gap (#1202) and two open Mars definition tasks (MD-10, MD-11).

Page numbers below are the white paper's unless marked otherwise. The paper is about Mars. The Moon appears only in Apollo history and in one closing sentence (p. 4).

What it is¶

Two directions (p. 2):

Forward planetary protection "is primarily a science and stewardship consideration". At Mars it "aims to control the introduction of contamination from Earth that could be harmful to science. This is especially critical for the search for evidence of present or past life." It can cause "false positives (e.g., finding biosignatures on Mars that are actually from Earth-origin organisms or materials) or false negatives (e.g., being unable to detect a true Mars biosignature because of background noise from Earth-origin contamination)".
Backward planetary protection "is a safety consideration". It "safeguards Earth's biosphere (which encompasses the environment, flora, and fauna, including humans) from returned material that may contain hazardous extraterrestrial organisms or bioreactive molecules".

Key terms (p. 1):

Term	NASA's definition
Forward Planetary Protection	"Harmful contamination of other planetary bodies (e.g., planets, moons, and asteroids) by Earth-origin material."
Backward Planetary Protection	"Introduction of potentially hazardous material from exploration destinations to Earth's biosphere."
Bioburden	"The number of microorganisms present on or in an object (e.g., spacecraft hardware)"
Biosphere	"The area of a planetary body and its atmosphere occupied by living things."
Harmful Contamination	"Unwanted material that damages the integrity of scientific investigations or has negative consequences for humans or Earth's biosphere."

The legal basis. "Planetary protection is also an obligation of the Outer Space Treaty of 1967": States Parties shall "conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter" (p. 1). ADD Rev C makes the same point under its Responsible Use tenet: Article IX covers forward and backward contamination, "typically managed under planetary protection" (ADD Rev C, p. 95; RT-6).

Crewed missions are not yet covered. NASA's current policy documents are "for robotic missions" (p. 1; Table Two below). "A 2020 interim directive directed NASA to develop risk-informed planetary protection implementation strategies for human deep space missions, including" (p. 1):

"Capabilities to monitor biological processes associated with the human presence in space exploration and to evaluate changes over time."
"Technologies for mitigating contamination release or intrusion, potentially including closed-loop systems; cleaning/re-cleaning capabilities; quarantine, support systems, and biological waste disposal that minimize impact of humans on the environment of Mars."
"An understanding of environmental processes on Mars that would contribute to transport and inactivation of terrestrial organisms released by human activity."

What Viking and Apollo did, and why it is not enough for crews¶

"The Apollo and Viking programs laid the foundation for current planetary protection approaches" (p. 2).

Forward, from Viking. Viking "established forward planetary protection processes, including the bioburden accounting practices used for robotic missions to Mars". The robotic approach samples hardware, heats or chemically treats components, and verifies "that the overall bioburden meets a required cleanliness level prior to launching the hardware" (p. 2).
Why that fails for crews. "While a robotic spacecraft bioburden can be measured before launch and treated as static (i.e., a set level), crew members' microbiomes and habitation environments will be active sources of microbial growth. Regardless of the cleanliness of spaceflight hardware, humans on the Martian surface represent a continuous contamination source" (p. 2). So "NASA needs to model the types and amount of contamination crew would generate" and "improve Mars environment models to better understand the transport, growth potential, and survivability of terrestrial contamination" (p. 2).
Backward, from Apollo. Apollo used "sample isolation and assessment and crew quarantine". Its lesson: "it takes time to properly prepare for and implement backward planetary protection, especially when engaging the wide range of stakeholders involved". Return facilities "can take years to develop". The Lunar Receiving Laboratory at Johnson isolated astronauts and assessed Apollo samples; "Mars samples will require similar dedicated facilities" (p. 2; Figure One, p. 3, shows Apollo 11's command module arriving there).
Hatch opening. "During the Apollo 11 mission, the crew exited the spacecraft in the ocean before entering quarantine. If NASA decided this procedure was insufficient for Mars missions, the agency would need to implement alternate designs and operations" (p. 2).
Restricted return. OSIRIS-REx's Bennu samples were classed "for unrestricted Earth-return". "In contrast, Mars samples — whether returned by crewed or robotic missions — would be classified for restricted Earth-return due to the potential for Mars-origin organic or bioreactive materials" (p. 2).

Who is involved¶

From "Planetary Protection Policy Participants" (p. 3):

The Outer Space Treaty. "As a party to the treaty, the United States government is responsible for activities of both governmental and non-governmental space actors (e.g., industry and academia)."
COSPAR. NASA contributes to the Committee on Space Research Planetary Protection Policy, "the accepted standard for international planetary protection compliance under the Outer Space Treaty".
Presidential approval. "For backward planetary protection, NASA implementation practices would require presidential approval, as outlined in Presidential Directive/National Security Council #25."
Other agencies. "the U.S. military, Federal Aviation Administration for launch and re-entry licenses, the Centers for Disease Control and Prevention for biohazard expertise, and the Environmental Protection Agency for sample return landing site considerations".
Workshops. With ESA, COSPAR and others, NASA "hosted a series of workshops between 2015 and 2022. These workshops identified key planetary protection knowledge gaps and outlined principles for planetary protection for human exploration missions, recognizing the inadequacy of traditional robotic mission protocols."

Architectural implications for crewed Mars missions¶

"The planetary protection strategies that NASA adopts for human missions to Mars will have wide-reaching, cross-cutting implications for the Mars architecture" (p. 4, PDF reading order). The paper calls them "a trade space that NASA, partners, and stakeholders will need to explore and address" (p. 4). Its examples (p. 4):

Where crews go. Planners "may wish to control crew access to (and avoid contamination of) regions that are more likely to harbor evidence of life, leaving those exploration tasks to 'clean' robots. Identifying these locations could require additional landing site data."
Special regions. "Activities like core sample drilling or nuclear fission power generation may require NASA to establish regions with special planetary restrictions beyond the baseline for other activities."
Samples. Methods for "sample collection, processing, conditioning, and storage on Mars that are compatible with containment and curation methods on Earth".
Suits. Current suits "operate at positive pressure" and "tolerate small amounts of leakage, but uncontrolled leakage from a space suit on Mars presents a potential planetary protection risk by releasing human contaminants onto the Martian surface".
Waste. "Apollo missions discarded human waste on the lunar surface, where microbes were unlikely to survive. Mars missions will likely require a different operational paradigm … NASA may determine that Mars missions must securely contain, destroy, or return with astronaut waste."
Transportation. "Mars transportation systems may also require planetary protection–specific design considerations. Examples could include sterilization of landers and ascent vehicle hardware elements, or 'break the chain' protocols, in which crew members and sealed samples are transferred from a potentially contaminated Mars ascent vehicle to 'Mars-free' Earth transfer vehicle."
From the start. Compliance must be considered "throughout the element design lifecycle, from the pre-project phase, through requirements development and design maturation, to flight certification. Planetary protection is not a sub-system that can be added to an architecture; instead, engineers and mission planners must account for planetary protection at the system and sub-system level for any hardware element."

Table One: example design considerations¶

"Example Design Considerations for Planetary Protection" (p. 4, read from the PDF; the text layer drops the Forward and Backward grouping):

	Architecture Element	Planetary Protection Considerations	Example Mitigation
Forward	EVA Suits	Leaks on joints and seals	Microbial monitoring, particle control and filtration technologies
Forward	Waste Management	Disposal on surface	Containment, sterilization of waste
Forward	Surface Habitat/Airlocks	Leaks or venting into atmosphere or surface from habitat	Microbial monitoring, particle control and filtration technologies
Forward	Surface Mobility Element	Sample collection cleanliness, hardware cleanliness, leaks or venting into the atmosphere or surface from hardware	Microbial monitoring, particle control and filtration technologies, microbial reduction/sterilization techniques
Backward	Sample Return	Break the chain of contact with Mars for collection systems	Particle control, filtration technologies, sterilization techniques
Backward	Earth Return Facility	Crew quarantine capability, post-mission vehicle isolation	Biosafety quarantine, sterilization techniques, sample safety assessment protocols, crew health monitoring

These "architecture elements" are generic types, not names from the ADD's element list (Elements). For Humans to Mars, "Mapping of elements to use cases and functions … is forward work" (ADD Rev C, p. 38; Humans to Mars).

What NASA is doing¶

Knowledge gaps. "NASA has identified planetary protection knowledge gaps … These knowledge gaps include capability shortfalls in microbial and human health monitoring; technology and operations for contamination control; and in understanding the natural transport of contamination on Mars" (p. 4).
A roadmap. "The agency is developing a roadmap to manage these knowledge gaps and integrate planetary protection into NASA's Moon to Mars Architecture as design concepts evolve" (p. 4).
Early in design. NASA is developing "refined planetary protection policies and practices to mitigate forward and backward contamination risks from crewed missions to Mars early in the architecture development effort, because these policies have implications at all phases of crewed Mars mission design" (p. 5).
Beyond Mars. "Exploration efforts will need to consider robust, comprehensive planetary protection approaches that consider unique environments of, and support exploration objectives for, the Moon, Mars, and other destinations" (p. 4).

NASA's policy framework (Table Two)¶

"NASA Planetary Protection Policy Framework" (p. 5):

Level	Document	What it is (p. 5)
Directive	NASA Policy for Safety and Mission Success (NPD 8700.1F)	"This NPD outlines NASA's policy to protect the terrestrial and planetary environments, and the public."
Procedural Requirements	Planetary Protection Provisions for Robotic Extraterrestrial Missions (NPR 8715.24)	"This NPR contains content on mission planetary protection categorization and project roles and responsibilities."
Standard	Implementing Planetary Protection Requirements for Space Flight (NASA-STD-8719.27)	"This standard outlines requirements for planetary protection forward and backward contamination control and cleanliness assays."
Handbook	NASA Planetary Protection Handbook (NASA/SP-20240016475)	"This handbook is intended to be a one-stop-shop for current planetary protection implementation knowledge and practice."

Where it appears in the architecture¶

Technology gap #1202, Planetary Protection Technologies for Human Exploration (rating 44, Mars only). Its state of the art cites three of the four Table Two documents, and says "Life support systems and airlocks vent unfiltered gas to environment" (tech gaps spreadsheet, ESDMD #1202).
Definition tasks MD-10 and MD-11, "Mars Forward Contamination Planetary Protection Risk Posture" and "Mars Backward Contamination Planetary Protection Risk Posture". Both are open: not shaded in the "Architecture Definition" white paper's Table One, not among ADD Section 3.1.3's completed tasks (Key definition tasks). The planetary protection paper never names them; the pairing is the wiki's.
Gaps that cite MD-10 or MD-11 in the spreadsheet: #0304 habitat environmental monitors (both), #0702 waste management (MD-10), #0803 Mars suits (MD-10) and #1202 (both). Three of these match rows of Table One by subject: suits, waste management, and habitat monitoring. The match is the wiki's.
RT-6 Responsible Use. The ADD's Outer Space Treaty, COSPAR and NASA-STD-8719.27 entries (RT-6).
The Moon Base Users Guide. "Planetary protection" is one of its Mars-forward areas: "Planetary protection practices protect the Moon and Mars from Earth-based contamination (forward contamination) and Earth from extraterrestrial contamination (backward contamination). Developing planetary protection principles and technologies for the Moon Base will help guide planetary protection for Mars missions" (Users Guide, p. 14; Mars-forward). The white paper doesn't mention the Moon Base.

Planetary protection white paper · #1202 · #0304 · #0702 · #0803 · #1201 In-Situ Sample Storage and Processing · Key definition tasks · RT-6 Responsible Use · Humans to Mars · Mars-forward

Sources¶

Planetary protection white paper, pp. 1–5 (all checked against the PDF) · ADD Rev C, pp. 38, 75–76, 95 · Tech gaps spreadsheet, ESDMD #1202, Definition Tasks column · "Architecture Definition" white paper, p. 5 · Users Guide, p. 14