Mars—Beyond the Red Horizon (28): Chapter 6 The Future of Mars Exploration—Recovery, Habitation, and Modification (2)
6.3 Human Exploration—From Surrogate Bodies to Human Bodies
Current Mars exploration is conducted entirely by unmanned machines. Rovers, landers, and orbiters. These are human "surrogate bodies." While remaining on Earth, humans "experience" Mars through these machines.
However, human exploration will fundamentally change this relationship.
Concepts for human Mars exploration have existed since the 1960s. Following the success of the Apollo program, there was a time when human Mars exploration was discussed as the next goal. But due to technical, budgetary, and political constraints, the plans were postponed repeatedly.
Currently, the most active entity in human Mars exploration is SpaceX. Elon Musk has set the construction of a Mars colony as the company's ultimate goal and is proceeding with the development of the large rocket "Starship." Starship is a fully reusable rocket designed for transporting personnel and supplies to Mars.
NASA also has a long-term human Mars exploration plan, with a concept involving coordination with the Artemis program, which uses the Moon as a transit point. However, the specific implementation timeline remains unclear.
The technical challenges of human Mars exploration are diverse.
Radiation—Mars has no magnetic field, and cosmic rays and solar particle events rain down directly. The radiation exposure during a round-trip flight from Earth to Mars is close to the upper limit of the current lifetime allowance for NASA astronauts. Radiation countermeasures are also necessary during surface stays.
Long-term effects of low gravity—Mars' gravity is 38 percent of Earth's. Long-term low-gravity environments lead to decreased bone density, muscle atrophy, and cardiovascular effects. Experience from the current International Space Station (ISS) shows that countermeasures are possible but difficult.
Psychological isolation—Communication delays between Earth and Mars range from 3 to 22 minutes depending on distance. Real-time communication is impossible, and the crew is placed in a situation of psychological isolation. Even in emergencies, immediate support from Earth cannot be received.
Landing and takeoff technology—The Martian atmosphere has only about 1 percent of the density of Earth's. Because the atmosphere is thin, the effect of aerobraking is limited, making the deceleration required for landing difficult. Technology to safely land personnel and large amounts of supplies has not yet been established.
Food and resources—For long-term stays, In-Situ Resource Utilization (ISRU) is necessary. This includes technology to recover carbon dioxide from the Martian atmosphere and decompose it into oxygen and carbon monoxide via electrolysis (the MOXIE experiment has been demonstrated on Perseverance), technology to obtain hydrogen and oxygen from water ice, and food production using soil.
What is important here is the fact that Mars is not "unreachable."
Using a Hohmann transfer orbit—a fuel-efficient orbit connecting Earth's orbit and Mars' orbit—one can reach Mars from Earth in about 7–9 months. This does not exceed the scale of an individual human lifespan. One day on Mars (1 Sol) is 24 hours and 39 minutes, almost the same length as a day on Earth. These numbers indicate that Mars is not a celestial body that is "too alien" for humans.
However, what is important is the fact that even if human Mars exploration is realized, one cannot exist without a spacesuit.
Humans cannot breathe the Martian atmosphere directly. The 95 percent carbon dioxide atmosphere cannot be used for breathing. The atmospheric pressure is far below the lower limit that the human body can withstand. On bare skin, the moisture in the body would boil.
Human experience on Mars is always mediated by an artificial environment. Spacesuits, habitat modules, pressurized rovers. Only through these artificial membranes can humans exist on Mars.
Mars is reachable, but it is not directly isomorphic to the Earth-bound body.
This is the most concrete form of the relationship that this book calls "virtual reality." Mars is physically real and reachable. However, humans cannot experience Mars directly. It always requires artificial mediation.
6.4 Sense of time on Mars—Transformation of the Earth-bound scale
When considering human exploration, there is another important question. That is the problem of time.
The flight to Mars takes 7–9 months. After arrival, one must wait at least a year or more for the next opportunity to return to Earth. This is due to the relationship between the orbits of Mars and Earth, with an optimal launch window occurring approximately every 26 months.
In other words, humans who head to Mars cannot return to Earth for at least two years (around three years including round-trip flight and stay).
This temporal constraint will change human perception. Events on Earth arrive as somewhat past occurrences, along with communication delays. Family, friends, society. They exist as a past delayed by 3 to 22 minutes.
In the night sky of Mars, one can see Earth. As a blue dot. It is a home, yet a place that cannot be reached.
This sensation is qualitatively different from what astronauts have experienced so far. The Earth seen from the ISS is nearby. The orbital altitude is about 400 kilometers, and the Earth is a massive presence right in front of one's eyes. However, from Mars, Earth is nothing more than a point in the night sky.
Humans who stay on Mars for a long time will live within a sense of time different from Earth's. It is an experience where the Earth-bound scale of time begins to subtly shift.
And here, the problem of "aging" appears again. When a human who has stayed on Mars for three years returns to Earth, will their body have aged in the same way as those who remained on Earth? Low gravity, radiation, psychological stress. These might accelerate aging. Or, they might age in a way different from Earth.
Mars is also a place that re-examines the human sense of time and the aging process itself.
(Published 2026.3.19)