Human mission to Mars

Travel to Mars

The energy needed for transfer between planetary orbits, or delta-v, is lowest at intervals fixed by the synodic period. For Earth–Mars trips, the period is every 26 months (2 years, 2 months), so missions are typically planned to coincide with one of these launch periods. Due to the eccentricity of Mars's orbit, the energy needed in the low-energy periods varies on roughly a 15-year cycle with the easiest periods needing only half the energy of the peaks. In the 20th century, a minimum existed in the 1969 and 1971 launch periods and another low in 1986 and 1988, then the cycle repeated. The last low-energy launch period occurred in 2023.

Several types of mission plans have been proposed, including opposition class and conjunction class, or the Crocco flyby. The lowest energy transfer to Mars is a Hohmann transfer orbit, a conjunction class mission which would involve a roughly 9-month travel time from Earth to Mars, about 500 days at Mars to wait for the transfer window to Earth, and a travel time of about 9 months to return to Earth. This would be a 34-month trip.

Shorter Mars mission plans have round-trip flight times of 400 to 450 days, or under 15 months for an opposition-class expedition, but would require significantly higher energy. A fast Mars mission of 245 day round trip could be possible with on-orbit staging. In 2014, ballistic capture was proposed, which may reduce fuel cost and provide more flexible launch windows compared to the Hohmann.[[File:Hubble Globes of Mars.jpg|thumb|Three views of Mars, [[Hubble Space Telescope]], 1997|left]]In the Crocco grand tour, a crewed spacecraft would get a flyby of Mars and Venus in under a year in space. Some flyby mission architectures can also be extended to include a style of Mars landing with a flyby excursion lander spacecraft. Proposed by R. Titus in 1966, it involved a short-stay lander-ascent vehicle that would separate from a "parent" Earth-Mars transfer craft prior to its flyby of Mars. The Ascent-Descent lander would arrive sooner and either go into orbit around Mars or land, and, depending on the design, offer perhaps 10–30 days before it needed to launch itself back to the main transfer vehicle. (See also Mars flyby.)

In the 1980s, it was suggested that aerobraking at Mars could reduce the mass required for a human Mars mission lifting off from Earth by as much as half. As a result, Mars missions have designed interplanetary spacecraft and landers capable of aerobraking.

Landing on Mars

A number of uncrewed spacecraft have landed on the surface of Mars, while some, such as Beagle2 (2003) and the Schiaparelli EDM (2016), have failed what is considered a difficult landing. Among the successes:

• Mars 3 – 1971
• Viking 1 and Viking 2 – 1976
• Mars Pathfinder and its Sojourner rover – 1997
• Spirit and Opportunity rovers – 2004
• Phoenix lander – 2008
• Curiosity rover – 2012
• InSight lander – 2018
• Tianwen-1 lander and Zhurong rover – 2021
• Perseverance rover and Ingenuity helicopter – 2021

Orbital capture

When an expedition reaches Mars, braking is required to enter orbit. Two options are available: rockets or aerocapture. Aerocapture at Mars for human missions was studied in the 20th century. In a review of 93 Mars studies, 24 used aerocapture for Mars or Earth return. One of the considerations for using aerocapture on crewed missions is a limit on the maximum force experienced by the astronauts. The current scientific consensus is that 5 g, or five times Earth's gravity, is the maximum allowable deceleration.

Survey work

Conducting a safe landing requires knowledge of the properties of the atmosphere, first observed by Mariner 4, and a survey of the planet to identify suitable landing sites. Major global surveys were conducted by Mariner 9, Viking 1, and two orbiters, which supported the Viking landers. Later orbiters, such as Mars Global Surveyor, 2001 Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter, have mapped Mars in higher resolution with improved instruments. These later surveys have identified the probable locations of water, a critical resource.

Funding

Sending humans to Mars will be expensive. In 2010, one estimate was roughly US$500 billion, but the actual costs will likely be more. Starting in the late 1950s, the early phase of space exploration was conducted as a space race by lone nations, as much to make a political statement as to study the Solar System. This proved to be unsustainable, and the current climate is one of international cooperation, with large projects such as the International Space Station and the proposed Lunar Gateway being built and launched by multiple countries.

Critics argue that the immense cost outweighs the immediate benefits of establishing a human presence on Mars and that funds could be better redirected toward other programs, such as robotic exploration. Proponents of human space exploration contend that the symbolism of establishing a presence in space may garner public interest to join the cause and spark global cooperation. There are also claims that a long-term investment in space travel is necessary for humanity's survival.

One factor to reduce the cost of sending humans to Mars may be space tourism. Growth in that business and technological developments would bring economies of scale and thus a lower cost of human spaceflight. A similar concept can be examined in the history of personal computers: when computers were used only for scientific research, with minor use in big industry, they were big, rare, heavy, and costly. When the potential market increased, and they started to become common in businesses and later in homes (in Western and developed countries), the computing power of home devices skyrocketed, and prices plummeted.

Medical

Main article: Space medicine

Several key physical challenges exist for human missions to Mars:

• Health threat from cosmic rays and other ionizing radiation.{{cite magazine |last=Fong, MD |first=Kevin

• Loss of kidney function. On 11 June 2024, researchers at the University College of London's Department of Renal Medicine reported that "Serious health risks emerge (with respect to the kidneys) the longer a person is exposed to (the Galactic Radiation and Microgravity that astronauts would be exposed to during a Mars mission)."

• Adverse health effects of prolonged weightlessness, including bone mineral density loss and eyesight impairment.{{cite web |last=Puiu |first=Tibi |access-date=February 9, 2012}}{{cite web

• Psychological and sociological effects of spaceflight involving long isolation from Earth and the lack of community due to lack of a real-time connection with Earth (compare Hermit).

• Social effects of several humans living under cramped conditions for more than one Earth year (possibly two or three years, depending on spacecraft and mission design).

• Lack of medical facilities.

• Potential failure of propulsion or life-support equipment. Some of these issues were estimated statistically in the HUMEX study. Ehlmann and others have reviewed political and economic concerns, as well as technological and biological feasibility aspects. While fuel for roundtrip travel could be a challenge, methane and oxygen can be produced using Martian H2O (preferably as water ice instead of liquid water) and atmospheric CO2 with sufficiently mature technology.

Planetary protection

Robotic spacecraft that travel to Mars require sterilization. The allowable limit is 300,000 spores on the exterior of general craft, with stricter requirements for spacecraft bound for "special regions" containing water. Otherwise there is a risk of contaminating not only the life-detection experiments but possibly the planet itself.

Sterilizing human missions to this level is impossible, as humans are typically host to a hundred trillion (1014) microorganisms of thousands of species of the human microbiota, and these cannot be removed. Containment seems the only option, but it is a major challenge in the event of a hard landing (i.e., a crash). There have been several planetary workshops on this issue, yet there are no final guidelines for a way forward. Human explorers would also be vulnerable to back contamination to Earth if they become carriers of microorganisms.

Mission proposal

Main article: List of crewed Mars mission plans

Over the past seven decades, a wide variety of mission architectures have been proposed or studied for human spaceflights to Mars. These have included chemical, nuclear, and electric propulsion, as well as a wide variety of landing, living, and return methodologies.[[File:ISS-Derived Deep Space Habitat with CPS.jpg|thumb|upright=1.4|Artist's rendering of the planned Orion/DSH/Cryogenic Propulsion Module assembly]]

A number of nations and organizations have long-term intentions to send humans to Mars.

• The United States has several robotic missions currently exploring Mars, with a sample-return planned for the future. The Orion Multi-Purpose Crew Vehicle (MPCV) is intended to serve as the launch/splashdown crew delivery vehicle, with a Deep Space Habitat module providing additional living space for the 16-month-long journey. The first crewed Mars Mission, which would include sending astronauts to Mars, orbiting Mars, and returning to Earth, is proposed for the 2030s. Technology development for US government missions to Mars is underway, but there is no well-funded approach to bring the conceptual project to completion with human landings on Mars by the mid-2030s, the stated objective.{{cite news |last=Berger |first=Eric
• The ESA has a long-term goal to send humans but has not built a crewed spacecraft . It sent robotic probes, such as ExoMars, in 2016 and planned to send the next probe in 2022, but the project was suspended due to Russia's invasion of Ukraine. , it was looking to send the probe in 2028 with assistance from NASA.

Technological innovations and hurdles

Significant technological hurdles need to be overcome for human spaceflight to Mars.

Entry into the thin and shallow Martian atmosphere will pose significant difficulties with re-entry; compared to Earth's much denser atmosphere, any spacecraft will descend very rapidly to the surface and must be slowed. A heat shield has to be used. NASA is carrying out research on retro-propulsive deceleration technologies to develop new approaches to Mars atmospheric entry. A key problem with propulsive techniques is handling the fluid flow problems and attitude control of the descent vehicle during the supersonic retropropulsion phase of the entry and deceleration.

A return mission from Mars will need to land a rocket to carry crew off the surface. Launch requirements mean that this rocket could be significantly smaller than an Earth-to-orbit rocket. Mars-to-orbit launch can also be achieved in single stage. Despite this, landing an ascent rocket back on Mars will be difficult.

In 2014, NASA proposed the Mars Ecopoiesis Test Bed.

;Intravenous fluid One of the medical supplies that might be needed is a considerable mass of intravenous fluid, which is mainly water, but contains other substances so it can be added directly to the human blood stream. If it could be created on the spot from existing water, this would reduce mass requirements. A prototype for this capability was tested on the International Space Station in 2010.

;Advanced resistive exercise device A person who is inactive for an extended period of time loses strength, muscle and bone mass. Spaceflight conditions are known to cause loss of bone mineral density in astronauts, increasing bone fracture risk. The most recent mathematical models predict 33% of astronauts will be at risk for osteoporosis during a human mission to Mars. A resistive exercise device similar to an Advanced Resistive Exercise Device (ARED) would be needed in the spaceship but would not fully counteract the loss of bone mineral density.

;Breathing gases While humans can breathe pure oxygen, usually additional gases such as nitrogen are included in the breathing mix. One possibility is to use in situ nitrogen and argon from the atmosphere of Mars, but they are hard to separate from each other.

An idea for keeping carbon dioxide out of the breathing air is to use reusable amine-bead carbon dioxide scrubbers. While one carbon dioxide scrubber filters the astronaut's air, the other is vented to the Mars atmosphere.

;Growing food

If humans are to live on Mars, growing food on Mars may be necessary – with numerous related challenges. Making soil useful for growing plants using existing Mars regolith is made more difficult by the lack of any organic material in the regolith and by the existence of about 0.5% perchlorates, a toxic salt that would damage the thyroid, kidneys and human cells in general. The environment is also too cold and lacks water except possibly at the poles.

In 2022, NASA co-funded a multi-year grant of US$1.9 million awarded to Arizona State University, the University of Arizona, and the Florida Institute of Technology to explore the idea of using Dehalococcoides mccartyi bacteria, among other microbes, to reduce the perchlorate content and add organic material to simulated Mars regolith. D. mccartyi also break down the perchlorates into harmless chloride and useful oxygen along with leaving organics in the soil as excretions and when they die, thus potentially solving several problems at one time.

Related missions

Some missions may be considered a "Mission to Mars" in their own right, or they may only be one step in a more in-depth program. Examples include planetary flyby missions, missions to Mars's moons, and study of the effects of the Martian environment on spacesuit materials by the Perseverance rover.

Missions to Deimos or Phobos

Many Mars mission concepts propose precursor missions to the moons of Mars, for example a sample return mission to the Mars moon Phobos – not quite Mars, but perhaps a convenient stepping stone to an eventual Martian surface mission. Lockheed Martin, as part of their "Stepping stones to Mars" project, called the "Red Rocks Project", proposed to explore Mars robotically from Deimos.

Use of fuel produced from water resources on Phobos or Deimos has also been proposed.

Uncrewed Mars sample return missions

An uncrewed Mars sample return mission (MSR) has sometimes been considered as a precursor to crewed missions to the Mars surface. In 2008, the ESA called a sample return "essential" and said it could bridge the gap between robotic and human missions to Mars. An example of a Mars sample return mission is Sample Collection for Investigation of Mars. Mars sample return was the highest priority Flagship Mission proposed for NASA by the Planetary Decadal Survey 2013–2022: The Future of Planetary Science.{{cite web |access-date=2015-11-03 |archive-url=https://web.archive.org/web/20110721054020/http://solarsystem.nasa.gov/2013decadal/ |archive-date=2011-07-21

Sample return plans raise the concern, however remote, that an infectious agent could be brought to Earth. Regardless, a basic set of guidelines for extraterrestrial sample return has been laid out depending on the source of sample (e.g. asteroid, Moon, Mars surface, etc.).

At the dawn of the 21st century, NASA crafted four potential pathways to Mars human missions, of which three included a Mars sample return as a prerequisite to human landing.

The rover Perseverance, which landed on Mars in 2021, is equipped with a device that allows it to collect rock samples to be returned at a later date by another mission. Perseverance, as part of the Mars 2020 mission, was launched on an Atlas V rocket on 30 July 2020.

Crewed orbital missions

Starting in 2004, NASA scientists have proposed to explore Mars via telepresence from human astronauts in orbit.

A similar idea was the proposed "Human Exploration using Real-time Robotic Operations" mission.

In order to reduce communications latency, which ranges from 4 to 24 minutes, a crewed Mars orbital station has been proposed to control robots and Mars aircraft without long latency.

References

References

1. Rich, Nathaniel. (25 February 2024). "Can Humans Endure the Psychological Torment of Mars? – NASA is conducting tests on what might be the greatest challenge of a Mars mission: the trauma of isolation.". [[The New York Times]].
2. JAXA. (2021-09-20). "Japan Space Agency: Why We're Exploring the Moons of Mars".
3. Von Drehle, David. (15 December 2020). "Humans don't have to set foot on Mars to visit it". [[The Washington Post]].
4. David S. F. Portree, ''[https://history.nasa.gov/monograph21/humans_to_Mars.htm Humans to Mars: Fifty Years of Mission Planning, 1950–2000]'', NASA Monographs in Aerospace History Series, Number 21, February 2001. NASA SP-2001-4521.
5. David S. F. Portree. ''[https://history.nasa.gov/monograph21/humans_to_Mars.htm Humans to Mars: Fifty Years of Mission Planning, 1950–2000]'', NASA Monographs in Aerospace History Series, Number 21, February 2001. Chapter 3, pp. 18–19. NASA SP-2001-4521.
6. Wooster, Paul D.. (2007). "Mission design options for human Mars missions". International Journal of Mars Science and Exploration.
7. David S. F. Portree. ''[https://history.nasa.gov/monograph21/humans_to_Mars.htm Humans to Mars: Fifty Years of Mission Planning, 1950–2000]'', NASA Monographs in Aerospace History Series, Number 21, February 2001. Chapter 3, pp. 15–16. NASA SP-2001-4521.
8. "Hohmann transfer orbit diagram".
9. "Homann Transfers".
10. (March 1964). "Popular Science". Bonnier Corporation.
11. Folta. (2012). "FAST MARS TRANSFERS THROUGH ON-ORBIT STAGING".
12. Williams. (28 December 2014). "Making A Trip To Mars Cheaper & Easier: The Case For Ballistic Capture". Universe Today.
13. "Crocco".
14. "To Mars by Flyby-Landing Excursion Mode (FLEM) (1966)".
15. "Photo-s88_35629".
16. Anderson, Gina. (2015-09-28). "NASA Confirms Evidence That Liquid Water Flows on Today's Mars".
17. Taylor, Fredric. (2010). "The Scientific Exploration of Mars". Cambridge University Press.
18. Sheetz, Michael. (September 26, 2020). "How SpaceX, Virgin Galactic, Blue Origin and others compete in the growing space tourism market".
19. Regis, Ed. (September 21, 2015). "Let's Not Move To Mars". [[New York Times]].
20. Scharf, Calib A.. (20 January 2020). "Death on Mars – The martian radiation environment is a problem for human explorers that cannot be overstated". [[Scientific American]].
21. (October 2006). "Model calculations of the particle spectrum of the galactic cosmic ray (GCR) environment: Assessment with ACE/CRIS and MARIE measurements". Radiation Measurements.
22. Shiga, David. (2009-09-16). "Too much radiation for astronauts to make it to Mars". [[New Scientist]].
23. (29 June 2013). "Atom & cosmos: Mars trip would mean big radiation dose: Curiosity instrument confirms expectation of major exposures: Atom & cosmos: Mars trip would mean big radiation dose: Curiosity instrument confirms expectation of major exposures". Science News.
24. Siew, Keith. (11 June 2024). "Cosmic kidney disease: an integrated pan-omic, physiological and morphological study into spaceflight-induced renal dysfunction". [[Nature Communications]].
25. Cuthbertson, Anthony. (12 June 2024). "Human missions to Mars in doubt after astronaut kidney shrinkage revealed". [[Yahoo News]].
26. Dr. Matt Midgley, [https://www.ucl.ac.uk/news/2024/jun/would-astronauts-kidneys-survive-roundtrip-mars Would astronauts' kidneys survive a roundtrip to Mars?], University College of London. 11 June 2024. Retrieved 13 June 2024.
27. [https://news.yahoo.com/news/human-missions-mars-doubt-astronaut-090649428.html Human missions to Mars in doubt after astronaut kidney shrinkage revealed] The Independent (UK). By Anthony Cuthbertson. 12 June 2024. Retrieved 13 June 2024.
28. (2020). "A human mission to Mars: Predicting the bone mineral density loss of astronauts". PLOS ONE.
29. (October 2011). "Optic Disc Edema, Globe Flattening, Choroidal Folds, and Hyperopic Shifts Observed in Astronauts after Long-duration Space Flight". Ophthalmology.
30. Strickland, Ashley. (15 November 2019). "Astronauts experienced reverse blood flow and blood clots on the space station, study says". [[CNN News]].
31. Marshall-Goebel, Karina. (13 November 2019). "Assessment of Jugular Venous Blood Flow Stasis and Thrombosis During Spaceflight". [[JAMA Network Open]].
32. (2006). "General human health issues for Moon and Mars missions: Results from the HUMEX study". Advances in Space Research.
33. (2005). "Humans to Mars: A feasibility and cost–benefit analysis". Acta Astronautica.
34. (2005). "2005 IEEE Aerospace Conference".
35. (23 May 2014). "Queens University Belfast scientist helps NASA Mars project".
36. (24 March 2011). "COSPAR Planetary Protection Policy".
37. (2007). "An Astrobiology Strategy for the Exploration of Mars". The National Academies Press.
38. (May 31, 2012). "When Biospheres Collide – a history of NASA's Planetary Protection Programs".
39. (2015). "Planetary Protection Knowledge Gaps for Human Extraterrestrial Missions".
40. (2002-05-29). "Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface". National Academies Press.
41. Wall, Mike. (27 August 2019). "Astronauts Will Face Many Hazards on a Journey to Mars – NASA is trying to bring the various risks down before launching astronauts to Mars in the 2030s.". [[Space.com]].
42. (1 Dec 2014). "Nasa's Orion spacecraft prepares for launch in first step towards crewed Mars mission".
43. (Dec 2, 2014). "We're sending humans to Mars! Watch our #JourneytoMars briefing live today at 12pm ET: #Orion". Twitter.
44. "NASA's Orion Flight Test and the Journey to Mars". NASA website.
45. Johnston, Ian. [https://www.independent.co.uk/news/science/mars-colonists-red-brick-houses-live-in-engineers-nasa-mission-donald-trump-a7705541.html "'Incredibly brave' Mars colonists could live in red-brick houses, say engineers"], ''[[The Independent]]'' (April 27, 2017).
46. "ExoMars rover".
47. Foust, Jeff. (2022-11-29). "ESA's ExoMars plans depend on NASA contributions".
48. "NASA Chief: We're Closer to Sending Humans on Mars Than Ever Before".
49. (2 December 2016). "Decades of attempts show how hard it is to land on Mars – here's how we plan to succeed in 2021".
50. (August 9, 2018). "Spinning heat shield for future spacecraft".
51. Hall, Loura. (2017-03-24). "Mars Ecopoiesis Test Bed". NASA.
52. (May 10, 2012). "A Solution for Medical Needs and Cramped Quarters in Space IVGEN Undergoes Lifetime Testing in Preparation For Future Missions". NASA.
53. "The Caves of Mars – Martian Air Breathing Mice". High Mars.
54. (30 September 2015). "Suiting Up for the Red Planet".
55. Rainey, Kristine. (7 August 2015). "Crew Members Sample Leafy Greens Grown on Space Station".
56. Scoles, Sarah. (27 November 2023). "Mars Needs Insects – If humans are ever going to live on the red planet, they're going to have to bring bugs with them.". [[The New York Times]].
57. Brown, David W.. (November 2024). "Red Mars, green Mars". Massachusetts Institute of Technology.
58. Brown, David W.. (November 2024). "Red Mars, green Mars". Massachusetts Institute of Technology.
59. (26 March 2025). "How NASA's Perseverance is Helping Prepare Astronauts for Mars - NASA".
60. (1 March 2014). "Manned sample return mission to Phobos: A technology demonstration for human exploration of Mars". CaltechAUTHORS.
61. Geoffrey A. Landis, "[http://www.sff.net/people/Geoffrey.Landis/Footsteps.pdf Footsteps to Mars: an Incremental Approach to Mars Exploration]", ''Journal of the British Interplanetary Society, Vol. 48'', pp. 367–342 (1995); presented at Case for Mars V, Boulder Colorado, 26–29 May 1993; appears in ''From Imagination to Reality: Mars Exploration Studies'', R. Zubrin, ed., ''AAS Science and Technology Series Volume 91,'' pp. 339–350 (1997).
62. Larry Page. [http://www.nasa.gov/pdf/604658main_5%20-%20Orion_MPCV_-Human_Space_Exploration_Workshop-_San_Diego1%201.pdf Deep Space Exploration – Stepping Stones] {{Webarchive. link. (2022-02-07 builds up to "Red Rocks: Explore Mars from Deimos".)
63. (20 April 2011). "One Possible Small Step Toward Mars Landing: A Martian Moon". Space.com.
64. European Space Agency. "Mars Sample Return: bridging robotic and human exploration".
65. Jones. (2008). "Ground Truth From Mars (2008) – Mars Sample Return at 6 Kilometers per Second: Practical, Low Cost, Low Risk, and Ready". [[Universities Space Research Association.
66. Rebuffat, D.. "Sample Return Missions Requirements for Earth Re-entry Capsules TPS".
67. "Next On Mars".
68. "Touchdown! NASA's Mars Perseverance Rover Safely Lands on Red Planet".
69. (5 December 2017). "Launch Windows".
70. (2008). "Teleoperation from Mars Orbit: A Proposal for Human Exploration". Acta Astronautica.
71. M. L. Lupisella, [http://www.lpi.usra.edu/publications/reports/CB-1089/lupisella.pdf "Human Mars Mission Contamination Issues"], ''Science and the Human Exploration of Mars'', January 11–12, 2001, NASA Goddard Space Flight Center, Greenbelt, Maryland. LPI Contribution, number 1089. Accessed November 15, 2012.
72. "HERRO Missions to Mars and Venus using Telerobotic Surface Exploration from Orbit". NASA Glenn Research Center.
73. (Oct 22, 2010). "1 of 4 Geoffrey Landis – HERRO TeleRobotic Exploration of Mars – Mars Society 2010".
74. (5 August 2012). "Time delay between Mars and Earth". European Space Agency.
75. "Marpost".