Why Moon to Mars¶
Summary. NASA's rationale for going to the Moon and Mars together. Nearly all human spaceflight experience is in low Earth orbit. As Mercury and Gemini led to Apollo in a "crawl-walk-run approach", lunar missions are meant to build the technology and operating experience that Mars needs. The white paper "Why Moon and Mars?" compares low Earth orbit, the Moon and Mars on distance, gravity and hazards. It groups what NASA must build up into four programmatic considerations, which the ADD calls four facets: American leadership (the ADD's "National Posture"), engineering and design, operations, and the human system. NASA "does not choose the Moon or Mars".
This page covers ADD Rev C Section 1.3.1 (pp. 14–15), ADD Appendix A (pp. 105–107), and the white paper, which the ADD points to for "Additional detail" (p. 15). Appendix A adds NASA's three pillars of exploration (science, national posture, inspiration) and a Venn figure. A 2024 white paper on why humans matter for science has its own section, with its own page numbers (below). So does the 2024 executive overview's "Why Moon to Mars?", an earlier and shorter form of the white paper's argument (below). Elsewhere, page numbers are marked "ADD" or "WP"; links go to the ADD Rev C source page and the white paper's source page.
The experience gap¶
"While humanity has over 60 years of human spaceflight experience, the vast majority of that experience is concentrated in low Earth orbit. NASA's history of human lunar exploration spans 9 Apollo missions on and around the Moon over the course of 5 years; only 12 humans have walked on the lunar surface. To date, only robotic missions have explored Mars. Exploring each destination requires a different scope and scale, driving specific challenges" (ADD Rev C, p. 14).
The white paper adds the low Earth orbit record: "The Space Shuttle program flew 135 flights, carrying a total of 355 people over the course of more than 30 years. NASA has also maintained a continuous human presence on the International Space Station for over 25 years." Its lunar count is "nine Apollo missions on and around the Moon (plus two Earth orbit missions) over the course of five years" (WP p. 2).
The three pillars of exploration (ADD Appendix A.1)¶
Appendix A opens with the question behind the whole architecture: "The systems engineering discipline that NASA uses to develop the Moon to Mars Architecture is predicated on motivation: what is the fundamental goal of exploration? Why send humans into space?" Its answer: "For NASA, the value of human exploration of the solar system is rooted in three pillars: science, national posture, and inspiration. Each pillar contains both unique and overlapping values; together, they form the value proposition for exploration" (ADD Rev C, p. 105).
"While different individuals prioritize different values, NASA, as a responsible steward of taxpayer dollars, must balance the entire landscape of motivations for exploring. This balance creates a robust, stable, and long-term architecture that will enable NASA to explore the Moon, Mars, and beyond" (ADD p. 105).
The p. 105 figure, "Three Pillars of Exploration", is a Venn diagram of three overlapping circles. It was read from the PDF, because the text layer drops it. Which region each label sits in is the wiki's reading of the image:
| Region | Labels |
|---|---|
| National Posture only | Global Influence · International Relationships |
| Science only | Biological · Heliophysics · Astrophysics · Planetary · Physical · Human Research |
| Inspiration only | STEM · Careers · Preserve Humanity · Cultural Enrichment |
| National Posture and Science | Advanced Science and Technology Priorities · Climate |
| National Posture and Inspiration | Norms |
| Science and Inspiration | Exploration |
| All three | Economy · Leadership · Human Condition |
Science (A.1.1, ADD pp. 105–106).
- "The pursuit of scientific knowledge — exploring and understanding the universe — is integral to the human space exploration endeavor."
- Exploration "teaches us about the earliest solar system environment: whether and how the bombardments of nascent worlds influenced the emergence of life, how the Earth and Moon formed and evolved, and how volatiles (e.g., water) and other potential resources were distributed and transported throughout the solar system."
- "Biological and physical systems can be observed in partial gravity, bringing out second- and third-order effects that are otherwise overwhelmed in the gravity environment."
- "The history of our Sun is preserved in lunar soil, examination of which enables solar activity predictions and space weather forecasts, which in turn support lunar and Martian exploration."
- "While remote sensing is a great aid, robotic and human exploration of other bodies in the solar system ultimately reap more data more effectively."
National posture (A.1.2, ADD p. 106).
- "By its very nature, achieving a vision of space exploration establishes national strength in science and technology innovation and competitiveness, which supports economic growth and global position."
- Spin-offs: "the term 'software engineering' was crafted for the development of the guidance and navigation systems on Apollo spacecraft. Food safety standards and telemedicine likewise originated with NASA's effort to enable longer-duration human space flight."
- "NASA's contracts and partnership with domestic commercial space resulted in $15 billion in private investments in space start-up companies in a single year, most of which were with US-based companies." The ADD gives no year or source for the figure.
- "Because there are no geographic bounds in space, exploration lends itself to international partnerships to achieve feats that might not otherwise be possible. Bolstering international partnerships, economic competitiveness, and global influence likewise reinforces national security interests."
Inspiration (A.1.3, ADD pp. 106–107).
- "The 'Moonshots' of the Apollo Program became a metaphor for how the nation could take on an audacious challenge and succeed through hard work and determination."
- "The International Space Station and other space partnerships model how people from many nations can live and work together toward a common purpose."
- "The next steps in space exploration can likewise inspire a new generation in science, technology, engineering, and mathematics studies that support the great enterprises of voyaging into space and overcoming the most difficult challenges on Earth."
The white paper names the same three pillars, in the order "national posture, science, and inspiration" (WP p. 1). In the ADD, "National Posture" is both a pillar (A.1.2) and the first of the four facets on p. 14 (below).
Earlier. The same Venn figure, with its labels in the same regions as the wiki reads both images, is Figure 3 of the 2024 white paper on international partnerships, captioned "Three pillars of exploration" (International Partnerships, p. 3). Two 2024 papers credit the pillars to NASA's Moon to Mars Strategy and Objectives Development document: "Science is one of the three pillars of NASA's Moon to Mars Strategy, alongside national posture and inspiration" (International Partnerships, p. 3), and "NASA's Moon to Mars Strategy and Objectives document outlines three pillars of exploration: science, inspiration, and national posture" (Responsible Exploration, p. 1).
The 2023 executive overview prints the Venn figure as its Figure 1, with the label "Advance Science and Technology Priorities" (PDF p. 2, read from the PDF). Both executive overviews define each pillar in one line under "Why Explore?": "Science: Investigations in deep space, on the Moon, and on Mars will enhance our understanding of the universe and our place in it." "National Posture: What is done, how it's accomplished, and who participates affect our world, quality of life, and humanity's future." "Inspiration: Accepting audacious challenges motivates current and future generations to contribute to our voyage deeper into space" (2023 overview, PDF p. 2). The 2024 overview adds "and to improve life on Earth" to the last (2024 overview, PDF p. 18).
In the 2023 strategy document¶
The 2023 Strategy and Objectives Development document is where the pillars first appear among the wiki's sources. Its Section 2.1, "Why Go?", reads (Strategy and Objectives Development, PDF p. 8):
- "Systems engineering is predicated on the motivation, which is the fundamental goal. Why do this? For the blueprint vision and Moon to Mars endeavor, along with its goals, objectives and subsequent architectural wireframe, the question is: Why send humans into space?"
- The value proposition "is rooted across three balanced pillars: science, inspiration, and national posture. Each pillar contains both unique and intersecting stakeholder values".
- "Uniquely, by balancing all the factors, NASA positions the Moon to Mars strategy for longevity and success: It is not subject to whims or leadership overhauls. Instead, it is rooted deeply in a broadly relevant, largely unchanging value system."
The figure (PDF p. 8, read from the PDF) is the Venn diagram above, with every label in the same region as the wiki reads both images. One label differs: "Advance S&T Priorities" here, "Advanced Science and Technology Priorities" in the ADD. Below it, a table labeled "VALUE" stands on three legs marked Science, Inspiration and National Posture.
ADD Appendix A.1 rewords this section (the wiki's comparison). Examples:
| 2023 (PDF pp. 8–9) | ADD Rev C (pp. 105–106) |
|---|---|
| "three balanced pillars: science, inspiration, and national posture" | "three pillars: science, national posture, and inspiration" |
| "While different individuals identify with different values, it's NASA's responsibility as a steward of taxpayer dollars to consider the entire landscape of motivating factors" | "While different individuals prioritize different values, NASA, as a responsible steward of taxpayer dollars, must balance the entire landscape of motivations for exploring." |
| "Biological and physical systems can be observed in reduced gravity, bringing out second and third order effects" | "…observed in partial gravity, bringing out second- and third-order effects" |
| "$15 billion in private investments in space start-up companies in a single year of this new era alone, with the majority of those investments in United States companies" | "$15 billion in private investments in space start-up companies in a single year, most of which were with US-based companies" |
Neither gives a year or a source for the $15 billion.
Benefit descriptions (Appendix A, PDF pp. 38–42). Each label in the Venn diagram gets a heading, a tagline and a paragraph. The taglines, as printed:
| Pillar or intersection | Label: tagline |
|---|---|
| Science | Human Research: "Understanding ourselves" · Heliophysics: "New vantage points" · Planetary Science: "Discoveries about geologic history" · Biological Science: "Understanding life away from Earth" · Astrophysics: "Radio quiet measurements" · Physical Science: "Understanding physical systems and processes in new environments" |
| Inspiration | STEM: "Inspiring the workforce of tomorrow" · Careers: "Work that makes an impact on humanity" · Preserve Humanity: "Thriving away from Earth" · Cultural Enrichment: "New perspectives spark creativity and drive innovation" |
| National Posture | Global Influence: "Championing the future" · International Relationships: "Opportunities to share and compound benefits among friends" |
| Science and Inspiration | Exploration: "Satisfying humanity's need to expand understanding of our place in the universe" |
| Science and National Posture | Advance Science and Technology Priorities: "Enabling the future through science and technology development" · Climate: "Understanding other worlds to safeguard our own" |
| Inspiration and National Posture | Norms: "Be the example; influence the rules of the road" |
| Science, Inspiration, and National Posture | Leadership: "Leading the way to a human future in space" · Economy: "Creating a sustainable ecosystem for innovation, exploration, and public benefit" · Human Condition: "Exploring space for the benefit of humanity" |
The heading "Advance Science and Technology Priorities" (PDF p. 41) is a third version of that label. The 2023 figure has "Advance S&T Priorities", the ADD figure "Advanced Science and Technology Priorities".
Examples of the paragraphs:
- Astrophysics: "The radio quiet far side of the Moon is a unique location to take sensitive measurements of the dark ages of the universe" (PDF p. 39).
- Preserve Humanity: "Living and working in isolated locations in the most extreme extraterrestrial environments will teach humanity how to survive and even thrive without Earth's support" (PDF p. 39).
- Norms: "Through exploration of the Moon, Mars, and other bodies, NASA and its partners create the rules of engagement that best serve their citizens, including norms for operational activities and advanced demonstrations of science and technology to shape the safe and sustainable use of space" (PDF p. 41).
- Economy: "Like today's Antarctic research bases and the International Space Station, early human efforts on the Moon and Mars will rely on a network of commercial, international, and other partners working together to support NASA's efforts. Over time, through the development of innovative new technologies and operations adapted to these extreme environments, these early efforts will pave the way toward more capable, sustainable, and increasingly Earth-independent operations" (PDF p. 42).
- Human Condition: "Being at the center of the Venn diagram, the human condition is tied to all other benefits of strategy". "Leadership, Economy, and Human Condition are inextricably intertwined at the center" (PDF p. 42).
What changed by Rev C (the wiki's comparison). The ADD keeps the Venn figure's labels but not the benefit descriptions (ADD Rev C, pp. 105–107). A search of its text for "Human Condition", "Norms" and "Climate" finds none of them in that sense. The figure's labels are in the image only, which the text layer drops.
Why humans, for science (ACR24 white paper, 2024)¶
Appendix A asks "Why send humans into space?" (ADD p. 105). For science, the 2024 white paper "Humans in Space to Accomplish Science Objectives" gives NASA's answer. It predates Rev C. Page numbers in this section are the paper's.
Robots first, humans where they add. "Teleoperated robotic probes are the primary means to conduct space science, but human explorers can enable or enhance particular types of science. Crewed missions are, of course, essential to investigations of the human body itself in space" (p. 1). The cost is stated: "Sending human explorers to other worlds requires larger, more complex, and more costly systems than purely robotic missions" (p. 1). The paper's motto, boxed: "Science enables exploration; exploration enables science" (p. 1). It uses "exploration" for "missions by humans beyond low Earth orbit" and "science" for the space science disciplines plus "physics, biology, chemistry, and studies of human physiology, psychology, and human health countermeasures in space" (p. 1).
What astronauts add (pp. 1–2):
- Judgment about samples. "Human explorers can understand the context and setting of a geologic sample, thinking independently to make sampling stops and adjusting traverse plans to take advantage of serendipitous sampling opportunities. They can collect the most valuable samples, which is essential given sample return mass constraints."
- Hands. Astronauts "are suited to tasks requiring complex movements, fine manipulation or dexterity, or hand-eye coordination", including "precision emplacement of scientific instruments, maintenance and calibration of scientific instruments, and operations of instruments".
- Deployed instruments. "Suitcase science" packages are "autonomous instrument packages installed on the lunar surface, either robotically or by astronauts". Geophysical and geochemical instruments benefit from "precise siting, alignment, and strong coupling with the surface or subsurface", which humans can do and "troubleshoot issues more effectively than robots".
- Reacting. "They can react to evolving mission parameters, turning unforeseen events into opportunities for discovery."
Where the research happens today. "Currently, the International Space Station and Earth-based ground analogues conduct most of the U.S.'s space-based biological and physical science research", and their lessons "are informing planning for the Artemis campaign and beyond" (p. 1). See RT-8.
The reports behind it. The paper quotes four: the National Research Council's The Scientific Context for Exploration of the Moon (2007), the planetary science decadal Origins, Worlds, and Life (2022), NASA's Artemis III Science Definition Report (headed "[2015]"), and a 2023 MEPAG Tiger Team report on science objectives for human Mars missions. All four call for human and robotic work together; the quotations are on the source page. The MEPAG team was tasked by SMD "with identifying science objectives for the Moon to Mars Architecture's Humans to Mars segment", and its findings "are easily applied to the Moon or other potential human destinations" (p. 3).
What changed by Rev C (the wiki's comparison):
- The goals carry the paper's point. LPS science is "best accomplished by on-site human explorers … aided by surface and orbiting robotic systems", and SE is to "Develop integrated human and robotic methods" (ADD p. 15; Objectives). A.1.1 says "robotic and human exploration … ultimately reap more data more effectively" (ADD p. 106, above).
- The Artemis III report is about a landing. Artemis III is now an Earth-orbit test (Human Lunar Return).
Crawl-walk-run¶
Why go at all. "NASA is sending humans back to the Moon and on to Mars to achieve its three pillars of exploration: national posture, science, and inspiration" (WP p. 1). "Both the Moon and Mars have science and technology objectives in their own right, but advancing the operational skills, techniques, and systems to conduct that work successfully is critical" (WP p. 1).
Apollo was not easy. "The triumph and speed of the Apollo Program have left a lasting impression that planetary exploration is relatively easy. This is not the case. The Apollo program's success depended on significant government investments in the U.S. industrial base and iterative development of exploration capabilities. By taking a crawl-walk-run approach, NASA built on increasingly ambitious objectives to develop the technologies and operational experience necessary to land on the Moon and safely return to Earth" (WP p. 1).
The ADD's version: "To prepare to land on the Moon in 1969, NASA followed an incremental programmatic approach. The agency learned that humans could live in space through the Mercury Program; learned to operate in space through the Gemini Program; and finally landed on the Moon and safely returned to Earth through the Apollo Program. Robotic precursor missions, like the Ranger and Surveyor projects, also paved the way for human exploration" (ADD p. 14). "The Moon to Mars Architecture follows a similar developmental approach, building foundational deep space exploration capabilities with lunar missions while preparing humanity's first journeys to Mars" (ADD p. 14).
The p. 2 graphic (WP p. 2, read from the PDF; the text layer drops it):
| Project Mercury | Project Gemini | The Apollo Program | |
|---|---|---|---|
| Icon | Crawl | Walk | Run |
| Years | 1961–1963 | 1964–1966 | 1967–1972 |
| Flights | "Six Crewed Flights" | "10 Crewed Flights" | "Nine Crewed Flights" |
| What it did | "NASA developed foundational spaceflight capabilities, successfully placed astronauts in orbits, and returned them safely to Earth." | "NASA bridged gaps between capabilities developed under Project Mercury and those needed to send humanity to the Moon." | "NASA leveraged lessons learned, technologies developed, and astronauts trained during Mercury and Gemini to send crews to the Moon." |
| Objectives | "Place a crewed spacecraft in orbit." "Investigate human performance in space." "Recover astronauts and spacecraft safely." | "Test astronauts' ability to fly long-duration missions." "Understand spacecraft rendezvous and docking." "Perfect re-entry and landing methods." | "Land humans on the Moon and return them to Earth." "Live, work, and conduct science on the lunar surface." "Establish capabilities that meet national interests." |
The graphic's "Nine Crewed Flights" for Apollo differs from the text's "nine … (plus two Earth orbit missions)" on the same page; both are quoted as printed.
Today. "NASA builds on the success of Apollo and the International Space Station, taking a similarly incremental, programmatic approach with its Moon to Mars Architecture … Just as Mercury and Gemini laid the foundation for Apollo, the continued innovation in low Earth orbit and Artemis lunar campaign will empower parallel development and execution of the first crewed missions to the Red Planet" (WP p. 1). The 2025 Architecture Update summarizes the paper as "an evolutionary crawl-walk-run approach" (2025 Architecture Update, p. 17).
Three challenges: distance, gravity, hazards¶
"Humanity's experiences at these three destinations inform one another, but there are also unique considerations that our experiences do not account for. This paper organizes them into three categories: distance, gravity, and hazards" (WP p. 2).
The p. 3 graphic, "Exploration Challenges by Destination" (WP p. 3, read from the PDF; the text layer drops it). The first row is drawn as Earth with an orbit ring; in the text, 250 miles is the space station's altitude (WP p. 2):
| Low Earth orbit | Moon | Mars | |
|---|---|---|---|
| Distance from Earth | "250 Miles" | "250,000 Miles" | "35,000,000 Miles" |
| One-way journey | "Hours" | "Days" | "Months" |
| Light-time delay | "Negligible" | "Seconds" | "4-24 Minutes" |
| Gravity | "microgravity" | "16.6% Earth Gravity", "1% Earth Mass" | "38% Earth Gravity", "10% Earth Mass" |
The distances need the text's qualifiers: the Moon's 250,000 miles is "At its farthest", and Mars's 35,000,000 is the planets' "closest recorded encounter … in 2003"; "the two planets can be separated by as much as 250,000,000 miles" (WP p. 2).
Distance (WP p. 2). "Missions to low Earth orbit, to the Moon, and to Mars are measured in hours, days, and months, respectively. Autonomy and self-sufficiency become increasingly important as the light-time communications delay grows from negligible to a major operational consideration."
- The Moon: "about three days to reach", and "Artemis astronauts can expect total latencies of up to 14 seconds".
- Mars: "a one-way light-time communications delay between 4 and 24 minutes, making real-time conversation with Earth impractical". The 2025 Architecture Update, from the same month, says "a one-way time delay of up to 22 minutes" (Update, p. 13; open question 31).
- "Mission distance and duration can also have psychological and psychosocial effects that NASA must understand before sending crews into deep space."
Gravity (WP pp. 2–3). Leaving a gravity well takes energy, measured as delta-v. "The propellant required to achieve this delta-v for a given payload is a mass multiplier often called a 'gear ratio.' The gear ratio for a Mars mission is much greater than a Moon mission. In other words, it takes significantly more energy to deliver one kilogram of mass to Mars." And on the surface: "systems and operational paradigms designed for microgravity will not inherently work in these partial-gravity environments" (WP p. 3).
Hazards (WP p. 4). Moon and Mars missions bring "challenges that cannot be tested on the microgravity platform. These challenges include radiation, dust, and transitions between a new set of gravity environments."
- Radiation. Earth's magnetosphere protects low Earth orbit; "Neither the Moon nor Mars has a similar protective feature."
- Dust "can be detrimental to crew health, and can damage hatch seals or reduce solar array performance". NASA must "ruggedize space systems developed for relatively pristine orbital environments so that they can operate in dusty planetary environments."
- Gravity transitions "will impact the human system in ways that NASA must understand to ensure safety and success."
- Why the Moon first. "NASA can better understand these hazards by studying astronauts and testing systems at the Moon, where mission support is readily available from Earth and an abort could return crew relatively quickly. This paradigm would better prepare the agency for Mars missions, where support is limited and mission aborts may not be feasible or could take months."
ADD Section 3.1.1 makes similar points as "unique considerations" by destination (pp. 72–73): see Architecture definition process.
Four programmatic considerations¶
"Just as the Apollo Program required sustained, programmatic investments, a campaign of Moon to Mars exploration will be evolutionary. It will rely on thoughtful programmatic approaches that this paper organizes into four categories: American leadership, engineering and design, operations, and human systems" (WP p. 4).
Two names for the same four. The ADD calls them facets: "NASA's approach builds capabilities across four facets" (ADD p. 14). The match below is the wiki's, by wording; the full comparison is on the white paper's source page.
| ADD facet | White paper heading | NASA's wording (ADD p. 14; WP pp. 4–5) |
|---|---|---|
| National Posture | American Leadership | ADD: "The Moon to Mars campaign will reinforce the United States' global leadership in space exploration. This includes developing the nation's industrial base, advancing technologies, and expanding economic utilization at the Moon and Mars." The WP has "will require and enable" for "will reinforce". |
| Engineering and Design | Engineering and Design | "The design and deployment of hardware necessary to reach a destination become increasingly challenging as the distance from Earth grows. The performance needed for a Mars mission is far greater than for a Moon mission, which is far greater than for a low Earth orbit mission." (identical) |
| Operations | Operations | ADD: "While NASA and partner space agencies have decades of human spaceflight experience, that experience has mostly been near the Earth. Humanity must develop experience and competency to operate in increasingly remote environments. Closing this gap is a key facet of Moon to Mars activities." The WP has "decades of flight experience". |
| The Human System | Human Systems | ADD: "Even the shortest missions to Mars will likely exceed the longest stays aboard the International Space Station; NASA will need to ensure that astronauts can respond to extended deconditioning in microgravity, changes in gravity, prolonged isolation and confinement, deep space radiation, and other hazards." WP: "The survival of the human system is the most important aspect of any crewed exploration mission. For NASA, safety is paramount to mission success." |
The paper's takeaways call the four "national posture, engineering design, mission operations, and human systems" (WP p. 8). "National posture" is also the first of the three pillars of exploration (WP p. 1); here it names the consideration.
The p. 7 diagram (WP p. 7, read from the PDF; the text layer has no text for the page) hangs sub-headings off each consideration:
| Consideration | Sub-headings |
|---|---|
| American Leadership | Space Leadership · Partnerships · Technology Readiness · Economic Development |
| Engineering and Design | Vehicle Design · Supplies and Logistics · Maintainability and Reusability |
| Operations | Autonomy and Earth-Independence · Coordination and Aggregation · Risk and Contingency Planning |
| Human Systems | Operational Experience · Health Hazards (Space Radiation · Isolation and Confinement · Distance from Earth · Altered Gravity Fields · Hostile/Closed Environments) |
American leadership (WP p. 4)¶
- Space leadership. NASA-led collaborations "will follow the Artemis Accords, which implement the commitments by signatory nations to 1967's Outer Space Treaty", the UN Registration Convention and the UN Rescue Agreement. See RT-6 Responsible Use.
- Partnerships "enable NASA to engage a wider industrial and supply base, expand the range of ideas and systems that the agency can leverage, and increase the speed of innovation. Partnerships can offer parallel development opportunities, improve robustness through redundancy, and contribute to economic development." See RT-1 and RT-2.
- Technology readiness. "Technology innovation and iteration at the Moon will help NASA develop the high-reliability capabilities needed for Mars missions, where repair and replacement may be infeasible." The example is fission: NASA selected it in 2024 as Mars's primary surface power technology, and "Using this same technology for NASA's lunar surface infrastructure accelerates technology development into a flight project and reduces risk for subsequent Mars applications" (see Lunar Nuclear Fission System). "Commercial and international partners can invest in technology development efforts to fill architecture-driven technology gaps and enable exploration" (see Gaps index).
- Economic development. "The magnitude of Moon to Mars exploration requires the activation of the American industrial base … It also means fostering new companies and industries that will compete to offer cost-effective services to the U.S. government and economic benefit to the American people." See RT-9.
Engineering and design (WP pp. 4–5)¶
- Vehicle design. "Only one launch vehicle — the Space Launch System — is certified for human launches beyond low Earth orbit today", and the U.S. "currently has only one vehicle rated for lunar exploration — the Orion spacecraft. Mars transportation vehicles exist only as early concepts." Mars "will require development of new or enhanced vehicles to ensure a robust architecture with appropriate redundancy." See SLS and Orion.
- Supplies and logistics. "NASA projects annual logistics needs of 5,000 to 6,000 kgs for four crew members operating on the lunar surface for approximately 30 days." The paper cites the 2024 white paper "Lunar Surface Cargo" for this (reference 31). That paper's text doesn't contain the figure. It forecasts 2,500 to 10,000 kg of cargo a year; the companion mobility paper has "four crew members … for approximately 30 days" and logistics of "2,000 to 6,000 kg per crewed surface mission" (Lunar Surface Cargo; open question 45). "Mars missions, which could last two to three years, would require significantly more logistics and would likely need them positioned on Mars prior to launching human explorers." See Logistics Systems.
- Maintainability and reusability. "NASA estimates that similar maintenance tasks could take up over 24 hours of crew time over the course of a 28-day lunar surface mission", citing an NTRS paper (reference 32). Missions far from Earth "would need to operate uncrewed for long periods of time. NASA will need to demonstrate this advanced system reliability, which far exceeds the International Space Station's capabilities, to prepare for Mars missions." See RT-5 and RT-4.
Operations (WP p. 5)¶
- Autonomy and Earth-independence. "Increasing distance and communication delays at the Moon and Mars will greatly reduce Earth-based flight control operations support, necessitating development of Earth-independent and autonomous capabilities." See Autonomous Systems and Robotics.
- Coordination and aggregation. "one Saturn V rocket launched everything needed for surface operations at the lunar equator. In contrast, Artemis campaign objectives for the lunar South Pole region call for a multi-launch, multi-partner architecture that considers interoperability and aggregation of systems at exploration sites. Mars architectures will be even more complex, requiring perhaps dozens of launches and landings to aggregate required systems." For scale: ISS assembly "required more than 40 missions and over 260 spacewalks". See RT-7 Interoperability.
- Risk and contingency planning. "Aborts from low Earth orbit are possible in a matter of hours, while aborts from cislunar space and the lunar surface would take days. During Mars missions, however, aborts could take much longer, on the order of months, or, depending on orbital dynamics and the phase of the mission, might not be possible at all." See RT-3 Crew Return.
Human systems (WP pp. 5–6)¶
- Health hazards. "The five main hazards of human spaceflight are space radiation, isolation and confinement, distance from Earth, altered gravity fields, and hostile/closed environments. These hazards are especially heightened by the distance, duration, and complexity of Mars missions." Low Earth orbit techniques such as exercise protocols "will be extensible", but Moon and Mars missions "will also require new design solutions, health countermeasures, operational paradigms" (as printed). See Human Systems.
- Operational experience. "Experience, medical data, and lessons learned from lunar operations will buy down risk for future Mars missions." "NASA's longest human spaceflight record, 371 days, is only about half of the duration of the shortest anticipated Mars mission." "It could take days of readaptation to Martian gravity for astronauts to perform an EVA." "Increasing the duration of lunar surface missions, with the Moon serving as an analog for Mars, will give NASA the opportunity to study how the human body reacts to those transitions and refine its operational approach and medical countermeasures for the first human Mars missions."
In the 2024 executive overview¶
A year before the white paper, the 2024 executive overview opened with a two-page "Why Moon to Mars?" (PDF pp. 4–5). It is an earlier, shorter form of the same argument, and some of its sentences reappear in the ADD and the paper. Page numbers in this section are the overview's PDF pages.
The question. "The extraordinary triumph of the Apollo program has left a lasting impression that lunar exploration is relatively easy and of limited value today. Why then should humanity return to the Moon before sending crews to explore of Mars and beyond?" (PDF p. 5; "explore of" as printed). Its answer runs through the segments: "After the initial Artemis missions of the Human Lunar Return segment, activities in the lunar Foundational Exploration segment will prove the technologies, capabilities, and systems needed for the Humans to Mars segment. The Sustained Lunar Evolution segment will see increased scientific and commercial utilization of the Moon while government-led development continues toward the next horizon" (PDF p. 5).
The infographic (PDF p. 4, read from the PDF; the text layer drops it). Two panels, "Exploration Challenges by Crew Destination" and "Exploration Experience by Crew Destination". Values as printed, with their tildes:
| "Orbital Missions": crew in low Earth orbit | "Moon Missions": crewed lunar exploration | "Mars Missions": crewed Mars exploration | |
|---|---|---|---|
| % of Earth gravity | "micro gravity" | "~17%" | "~38%" |
| Mean (average) distance | "~4 hundred km" | "~384 thousand km" | "~225 million km" |
| One-way delay | "~1 second" | "~1.2 seconds" | "~4-24 minutes" |
| Delta-v from LEO | "~20 m/s" | "~5 to 5.9 thousand m/s" | "~7.2 to 15.2 thousand m/s" |
| Experience | "7 Crewed Mercury Flights", "10 Crewed Gemini Flights", "135 Crewed Space Shuttle Flights", "20+ Years on the Space Station", "270+ Visitors to the Station" | "9 Crewed Apollo Missions", "1 Integrated Artemis Flight Test", "12 Explorers on the Surface", "5% Lunar Surface Explored" | "12 Successful Robotic Landings", "1% Mars Surface Explored" |
| Years | "60+ Years of Crew Experience (1962-present)" | "5 Years of Crew Experience (1968-1972)" | "Zero Years of Crew Experience (Exclusively Robotic Missions)" |
| Verdict | "Extensive Crew Experience" | "Minimal Crew Experience" | "Zero Crew Experience" |
A note beside the delta-v scale is too small to read reliably at page resolution. The axis names are shortened here from the printed "% of Earth Gravity", "Mean (Average) Distance", "One-Way Delay" and "delta-v from LEO".
Four key considerations. "Four key facets of the underlying rationale for using crewed lunar missions to prepare for the journey to Mars are national posture, engineering design, mission operations, and human systems" (PDF p. 5). Each has sub-headings, posed as questions. The 2025 paper's p. 7 diagram keeps most of them (above):
| Facet (2024) | Sub-headings (2024, PDF p. 5) | In the 2025 paper's diagram |
|---|---|---|
| National posture | Space leadership · Partnerships · Technology readiness · Economic development | the same four, under "American Leadership" |
| Engineering design | Vehicle design · Supplies and logistics · Maintainability and reliability | "Maintainability and Reusability" for the third |
| Mission operations | Autonomy and Earth-independence · Coordination and aggregation · Risk and contingency planning | the same three, under "Operations" |
| Human systems | Health hazards · Lessons learned | "Operational Experience" and "Health Hazards", with five hazards |
Four of the questions, as printed:
- Technology readiness: "What technology demonstration do we need to ensure the reliability and readiness of Mars-forward capabilities?"
- Autonomy and Earth-independence: "What is our concept of operations for missions so far from Earth that relying solely on terrestrial controllers becomes impractical?"
- Risk and contingency planning: "How can we buy down risk for Mars missions? How do we plan for contingencies when mission abort could take months or years?"
- Lessons learned: "How can we leverage human experience at the space station and on the Moon for longer and more distant flights?"
Takeaways. "Each progressive step from our home planet represents orders-of-magnitude increases in opportunity, challenge, and risk. A sustained exploration campaign that uses the Moon as a proving ground for Mars will allow NASA and its partners to gain and apply the knowledge and experience necessary to take the next giant leap." "Choosing to return to the Moon is not in opposition to humanity's journey to Mars. Lunar exploration will put Mars within our reach" (PDF p. 5).
What changed by Rev C and the 2025 paper (the wiki's comparison):
- Questions became a paper. The 2025 "Why Moon and Mars?" answers the overview's questions at length, and adds the distance–gravity–hazards frame and the crawl-walk-run history. Its takeaways reuse the overview's list word for word, "national posture, engineering design, mission operations, and human systems" (WP p. 8). Its closing lines are nearly the overview's: "Returning to the Moon is not in opposition to humanity's journey to the Red Planet" (WP p. 6).
- One name changed in the paper, not the ADD. The overview's "National posture" is the paper's "American Leadership" and the ADD's "National Posture" (ADD p. 14).
- The destinations paragraph is in the ADD. "Crewed lunar exploration spans 9 Apollo missions on and around the Moon over the course of 5 years; only 12 humans that have walked on the lunar surface. To date, only robotic missions have explored Mars" (PDF p. 5) is close to ADD p. 14 (above).
- The numbers moved. Distances: the overview gives means in kilometers, the paper "At its farthest" and closest-approach figures in miles (above). Gravity: "~17%" against the paper's "16.6%". Station years: "20+" against "over 25" (WP p. 2). The Mars delay is "4-24 minutes" in both, against the 2025 Update's "up to 22 minutes" (open question 31).
- Mercury, a contradiction. The overview counts "7 Crewed Mercury Flights"; the 2025 paper's crawl-walk-run graphic has "Six Crewed Flights" for Project Mercury (WP p. 2). The wiki prefers the newer figure and doesn't settle it (open question 53).
Not only technology¶
"In many cases, the capability gaps that NASA must address are not limited to technology. They also include experience and operational know-how. Just as early spaceflight missions paved the way for Apollo and decades of experience in low Earth orbit contributed to the Artemis program, lunar exploration will teach NASA to operate at Mars" (WP p. 6). The architecture's own lists of needs are the technology gaps and data gaps.
The Moon and Mars¶
"Lunar exploration serves dual purposes: conducting critical science on the Moon while building NASA's capacity to sustain human exploration and economic expansion on the lunar surface and cislunar space, operate in deep space, and enable the first human mission to Mars. The agency does not choose the Moon or Mars — parallel development through the Moon to Mars Architecture offers profound synergies that will empower NASA to send humanity further afield than ever before" (ADD Rev C, p. 14; the italics are NASA's).
The Purpose section says the same: the architecture "creates opportunities to execute ambitious missions to the lunar surface and the first human missions to Mars in parallel. Through near-term lunar exploration, NASA will institute the processes, procedures, and techniques needed to enable exploration of Mars and beyond" (ADD p. 11).
The white paper ends: "NASA will develop essential technology, capabilities, and operational experience at the Moon to reduce risk for Mars missions. Returning to the Moon is not in opposition to humanity's journey to the Red Planet. Lunar exploration will put Mars within our reach" (WP p. 6).
For how the Moon Base Users Guide carries this into Moon Base planning, see Mars-forward.
Where to read more¶
"Appendix A explores key architecture drivers and unique considerations for the Moon and Mars in more detail" (ADD Rev C, p. 15). Its own introduction promises "a deep dive into human exploration considerations for lunar and Mars exploration, including how NASA will build on the success of the Apollo Program and the International Space Station and develop new capabilities for exploring deep space" (ADD p. 105).
The appendix doesn't deliver that deep dive itself. Its section A.3, "Human Exploration
Considerations", is one paragraph that points to the white papers: "NASA has published many white
papers, available on the agency's Moon to Mars Architecture website, that explore these drivers in
depth. The white papers analyze specific explorations constraints and challenges, as well as how
these factors drive NASA's architecture roadmapping" (ADD p. 107, as printed, with footnotes to
nasa.gov/moontomarsarchitecture/ and nasa.gov/moontomarsarchitecture-whitepapers/; source pages:
main page, White Papers). The next page,
p. 108, is the Appendix B divider (PDF checked). So the depth on this page comes from the
"Why Moon and Mars?" white paper. A.2, the objectives, is on
Objectives: the ten goals.
Related pages¶
Objective decomposition · Objectives: the ten goals · Architecture definition process · Recurring tenets · Humans to Mars · Mars-forward · "Why Moon and Mars?" source page · ADD Rev C source page
Gaps on the paper's hazards (the pairing is the wiki's; the paper names no gap): dust, #0801 (Moon) and #0802 (Mars); radiation, #0307 and #0308; gravity transitions, #0402.
Sources¶
ADD Rev C, pp. 6, 11, 14–15, 72–73, 105–108 (PDF checked on pp. 105–108) · "Why Moon and Mars?" white paper, pp. 1–8 · 2025 Architecture Update, pp. 13, 17 · Humans in Space to Accomplish Science Objectives (ACR24), pp. 1–4 · International Partnerships (ACR24), p. 3 · Responsible Exploration (ACR24), p. 1 · Strategy and Objectives Development (2023), PDF pp. 8–9, 38–42 (PDF checked on pp. 41–42) · 2023 executive overview, PDF p. 2 · 2024 executive overview, PDF pp. 4–5, 18