What will humans wear when they arrive on Mars?

For a long time, humans have been full of curiosity and intimacy about Mars, a "terrestrial planet" located in the "habitable zone" of the solar system. In recent years, there has been a wave of immigration to Mars. But before immigration, we must consider the question of what humans need to wear to move freely on this "terrestrial planet" with a very harsh environment? Is it the same as the extravehicular suits that astronauts wear when they go out of the spacecraft in Earth orbit?

Martian environment

Mars is the most popular planet for exploration in the solar system and is also a candidate for planetary migration in science fiction works. Mars is the most easily observable terrestrial planet in the Earth's night sky. When it is closest to the Earth, its apparent magnitude is -2.94 (Note: Apparent magnitude is an astronomical term that refers to the brightness of a star as seen by the observer with the naked eye. The magnitude of the apparent magnitude can be negative. The smaller the value, the higher the brightness, and vice versa).

▲The true proportion of Earth and Mars

(Source: wikimedia)

Mars has a mass of 11% of Earth, a volume of 15% of Earth, and a surface gravity of 38% of Earth. It lost the protection of its atmosphere from the magnetosphere 4 billion years ago. After hundreds of millions of years of interaction with the solar wind, its atmosphere, which was originally more evaporable than Earth's, has become quite thin. Its surface atmospheric pressure is only 0.6% of Earth's, which is far below the Armstrong limit (6.18% of atmospheric pressure, at which the boiling point of water is equal to human body temperature). If humans were on Mars without any pressurization measures, all body fluids, including tears, saliva, and blood, would boil and evaporate in a very short time, and the lungs would be unable to exchange oxygen due to dehydration.

Of course, there is no need to worry too much about oxygen exchange, because there is basically no oxygen in the Martian atmosphere. The Martian atmosphere is about 96% carbon dioxide, 1.93% argon and 1.89% nitrogen, with trace amounts of oxygen molecules and water molecules. The dry Martian air is full of dust, including a large number of particles with a diameter of more than 2.5 microns (pm2.5). Although the composition of the Martian atmosphere reminds people of the primitive Earth atmosphere 2.3 billion years ago before the outbreak of cyanobacteria, its famous sandstorms will pull people back to the 21st century on the North China Plain.

Due to the lack of atmosphere and hydrosphere and its greater distance from the Sun, the average temperature on Mars is only -46 °C (-51 °F). In winter, the temperature in the polar regions can drop to -143 °C (-225.4 °F), while the temperature at the equator at noon in summer can reach 35 °C (95 °F).

▲Photo of Zhurong and the lander

(Source: China Planetary Exploration)

Without the protection of the atmosphere and global magnetic field, most of the surface of Mars is directly exposed to the solar wind. When the sun is calm, the surface radiation level is about 244.5 mSv per year. When the sun is active, the radiation will be even greater. On Earth, this value is about 6.2 mSv. According to the astronaut exposure standards established by the Multilateral Medical Operations Team (MMOP), the annual limit is 500mSv and the career limit is 1000mSv if protected.

Survive a minute

On Earth, you can live for about 80 years even without a space suit, but on Mars, you first need to consider how to survive the first minute. In the first minute, you don't have to consider comfort and durability, convenience of movement, work communication, metabolism, and you can even hold your breath without thinking about breathing, but you still have to consider issues, that is, isolating from the external environment and providing enough pressure for your body.

The earliest space suits were derived from aviation pressure suits. The inner layer is an airtight layer, which can maintain the airtightness and pressure of the suit in working state, and requires high-strength, elastic and sealed materials; the outer layer is a restrictive layer, which bears the residual pressure of the suit and maintains the anthropomorphic form of the space suit in the oxygen supply and pressurized state, and requires high-strength, inelastic materials. Currently, the airtight layer is generally made of polyurethane-coated nylon, and the restrictive layer is generally made of polyester.

Survive for an hour

After you survive the first minute, you will not only need to consider breathing, heat dissipation, temperature, and other issues related to human metabolism, but also how to protect yourself in a harsh environment. At this time, you need to build a heat dissipation layer inside the space suit and a thermal insulation and protection layer outside the pressure layer, as well as an environmental control system and a life support system.

Since the inside of the pressure suit is in direct contact with the human skin system, we can help dissipate heat and moisture through a nylon underwear with a water-cooled plastic tube system driven by a pump (liquid cooling ventilation suit).

The outer side of the pressure suit faces the external environment, so we use neoprene coated nylon and its outer aluminum-coated PET film to form a mixed fabric to form the thermal protection layer of the extravehicular space suit. In addition, in order to protect ourselves from the sandstorms on Mars and possible solar storms, we generally use aramid and Teflon materials with good heat-resistant, wear-resistant, waterproof and flame-retardant properties to create the outermost layer of armor outside the thermal protection layer.

▲Z-2 space suit life support system under development

(Source: wikimedia)

The life support system and environmental control system cannot be integrated into the clothes at present. You can only carry a large backpack that integrates various instruments such as oxygen supply, circulation ventilation, adjustment of internal pressure of the space suit, filtration of wastewater and exhaust gas, and monitoring of astronauts' physical indicators.

Able to work, study and live

Once you are able to survive, you need to consider indicators such as meeting long-term needs of work and life, portability, durability, comfort, and even how to work with engineering feasibility equipment such as the Mars rover.

▲China's space suit

(Source: Xinhua News Agency)

Mars has 38% of Earth's gravity, so the Martian suit cannot be too heavy, and the joints must have devices to assist movement. The need for flexible movement on Mars is greater than in microgravity. In terms of durability, although there is no serious chemical corrosion such as atomic oxygen on the surface of Mars, long-term low-pressure exposure in possible solar storms and dusty environments are serious problems. The NASA Perseverance Mars rover, launched at 19:50 on July 30, 2020, carried five types of materials for the outer layer of the extravehicular space suit to conduct field tests in the Martian environment.

Finally, I need to remind everyone that what humans wear on Mars is actually the idea of ​​developing a Martian suit from scratch, but in actual research and development, we are often affected by existing technology reserves, technological inertia, and even... money.

Today, no country has been able to land on Mars, but I believe that with the implementation of various countries' manned deep space exploration mission plans, the Mars space suits of major space powers will be available to us one after another, and from now on, what humans wear on Mars will no longer be a problem.

References:

[1] Li Guosheng, Zhang Yu. From space suit design to functional clothing research and development [J]. Beauty and Times: Aesthetics (Part 2), 2006(4):2.

[2] Wu Guoxing. Astronauts’ personal protective equipment – ​​space suits[J]. China Personal Protective Equipment, 2002.

[3] Li Min, Yu Miao. The development and current status of US cabin space suits[J]. 2021.

[4] Zhang Ruiming (translator). Design prospects of Russian planetary space suits[J]. Manned Spaceflight Information, 2010(3):5.

[5] Translated by Guan Chunlei, edited by Chen Jingshan. Space suit usage requirements and system solution evaluation for lunar and Mars missions[J]. Manned Spaceflight Information, 2008(1):15.

[6] Kou Cuicui. The influence of different space environments on the performance of extravehicular space suits[D]. Nanjing University of Aeronautics and Astronautics.

Scientific review: Yang Yuguang, China's space science ambassador, Vice Chairman of the International Astronautical Federation's Space Transportation Committee