Mars Entry, Descent, and Landing Challenges for Human Missions (ACR24 white paper)¶

Document: Mars Entry, Descent, and Landing Challenges for Human Missions, a six-page white paper headed "2024 Moon to Mars Architecture" and footed "2024 Moon to Mars Architecture Concept Review". No date is printed beyond the year; the download path is 2024/12. Files: text sources/text/docs/2024-12-acr24-mars-edl-challenges.txt; raw sources/raw/docs/2024-12-acr24-mars-edl-challenges.pdf (fetched 2026-10-01T07:22:46Z from https://www.nasa.gov/wp-content/uploads/2024/12/acr24-mars-edl-challenges.pdf, per sources/manifest.csv). Page numbers: the printed numbers (1–6) match the PDF pages and the text file's [page N] markers. PDF pages 2 to 5 were checked against the text; page 5 is all figures.

Which paper this is. NASA's White Papers web page lists it as "Mars Entry, Descent, and Landing Challenges": "Examines the challenges of landing on the Red Planet and considerations for crewed entry, descent, and landing capabilities" (White Papers page, fetched 2026-10-01). The 2024 executive overview lists it among its four "Mars-focused" papers (2024 overview, PDF p. 8). It doesn't cite the ADD. It is 2024 context, older than ADD Rev C.

Summary. "History provides numerous examples of the challenges of landing on Mars — only 12 out of 19 attempted robotic landings have been successful" (p. 1). The paper explains the three phases of entry, descent and landing (EDL), what makes Mars harder than the Moon or Earth (a thin atmosphere, surface hazards, plume-surface interaction, no full test on Earth), and why heritage systems, all scaled from Viking, can't land human-class masses. It names the areas of work: entry modeling and instrumentation, new deceleration systems, guidance and navigation, and landing systems. "This is a high-level overview" (p. 1). The content is on Transportation Systems.

Contents¶

Page	Section	Wiki home
1	Introduction; What is EDL?; Figure 1, Mars 2020's EDL sequence	Transportation Systems
2	Figure 2, landing ellipses; Entry; Descent; Landing; Historic Challenge of Mars EDL	same
3	Atmosphere; Surface Hazards; System Validation; Figure 3, the "Big Joe" boulder	same
4	Figure 4, ice exposed by Phoenix's engines; System Scalability; Transition to Human-Class Mars EDL	same
5	Figures 5–9	same; this page
6	Key Takeaways; References 1–10	this page

What the PDF shows that the text layer loses¶

Figure 2 (p. 2), "Mars Mission Landing Ellipses", overlays ellipses at one scale (bar marked 25, 50 and 100 km). As labeled: 1976 Viking 280 x 100 km; 1997 Pathfinder 100 x 20 km; 2004 Opportunity and Spirit 65 x 9 km; 2008 Phoenix 80 x 20 km; 2012 Curiosity 20 x 7 km; 2018 InSight 85 x 24 km; 2021 Perseverance 8 x 7 km; "Mars Human Landing Systems <0.1 km". A key marks guided and unguided ellipses. A note says "Mars map does not reflect historic or proposed Mars surface landing sites. Presented only to illustrate scale." The text layer keeps only the caption.

Figure 5 (p. 5), "Evolution of Mars EDL systems", is a table under the banner "Steady Progression of 'In Family' EDL Systems", with a last column marked "New Paradigm". Transcribed from the PDF:

Entry capsule	Viking	Pathfinder	MERs	Phoenix	Curiosity	InSight	M2020	Human-Scale Lander (Projected)
Diameter (m)	3.505	2.65	2.65	2.65	4.52	2.65	4.52	16+
Entry mass (metric ton)	0.930	0.585	0.840	0.573	3.153	0.608	3.368	49 - 65
Parachute diameter (m)	16.0	12.5	14.1	11.8	21.5	11.8	21.5	N/A
Landed mass (metric ton)	0.603	0.360	0.539	0.364	0.899	0.375	1.050	26 - 36
Landing altitude (km)	-3.5	-2.5	-1.4	-4.1	-4.4	-2.6	-2.5	+/- 2.0
Landing technology	Retropropulsion	Airbags	Airbags	Retropropulsion	Sky Crane	Retropropulsion	Sky Crane	Supersonic Retropropulsion

The capsule drawings are labeled "(to scale)".

Figures 6–9 (p. 5) are image collages with labels. Figure 6, "Entry modeling and simulation": Entry Vehicle Concepts; High-Fidelity Modeling; Sensors for Ground Test and Flight Validation. Figure 7, "New deceleration systems must be developed": Subscale Hardware and Flight Testing; Thermal Protection Systems; Supersonic Retropropulsion. Figure 8, "Development areas for guidance and navigation systems": GNC Systems Studies; Surface-Relative Sensing; Advanced Algorithms; High-Mach Entry Sensing; High-Resolution Surface Hazard Mapping. Figure 9, "Capability needs for landing systems and environments": PSI Modeling and Simulation for Analysis and Prediction; Flight Instruments for PSI Characterization and Mitigation; Mission Assessment and Landing-System Development.
Figure 1 (p. 1) labels Mars 2020's sequence; the text layer keeps the labels in order, from "Cruise Stage Separation" to "Rover Deployment".

Key takeaways (p. 6)¶

"While lunar landings help prepare NASA for the journey to the Red Planet, Mars landers encounter a variety of unique challenges not present on the Moon that must be understood and addressed. This includes the Martian atmosphere, surface hazards, plume-surface interaction, and terrestrial validation of systems intended for Mars."
"Robotic Mars landers have used variations on heritage designs that do not scale to the mass requirements of human-class Mars landers. To land larger vehicles on the Martian surface, NASA and its partners must develop and validate new technologies, including entry instrumentation, deceleration techniques, and navigation systems."
"Advances and testing by NASA and its partners will enable the agency to overcome the challenges of Mars EDL and successfully land humans on the Red Planet."

What changed by Rev C¶

These comparisons are the wiki's. In short: Rev C carries the paper's subject as two technology gaps (#1103, #1102) and three Mars data gaps, with targets that differ from the paper's figures in ways set out on Transportation Systems.

References that are other architecture documents¶

The paper cites ten references (p. 6). As printed:

Ref.	Title, as printed	Among the wiki's sources?
2	NASA's Moon to Mars Objectives	yes, Moon to Mars Objectives (2022) (same file name in the link)

The others are NASA's "Current and Past Missions to Mars" web page, the "Planetary Mission Entry Vehicles Quick Reference Guide Version 4.1", and seven journal and conference papers on Mars EDL, supersonic retropropulsion, map-relative localization, precise landing and plume effects. None is among the wiki's sources (sources/manifest.csv).

Oddities¶

As printed, PDF checked:

"Between 0.3 and 1 metric tons" against Figure 5. The text says "All flown EDL systems to date have had landed masses between 0.3 and 1 metric tons" (p. 4); Figure 5 gives M2020 1.050 t (p. 5).
"Over 20 metric tons" against Figure 5. The text says human-class EDL needs "an increase to landed masses in excess of 20 times greater, or over 20 metric tons" (p. 4); Figure 5's projected lander lands 26–36 t (p. 5). Not a contradiction, but two different figures.
References 8 to 10 are not cited in the text. The body cites [1] to [7] only (search of the text file; the figure captions carry no reference marks).
"Even when select landing ellipses that minimize hazards" (p. 3): a word seems to be missing.

See open question 66.

Transportation Systems · #1103 Mars Entry, Descent, and Landing · #1102 Mars Precision Landing and Hazard Avoidance · DN-004 M · DN-005 M · DN-006 M · Humans to Mars