Problems for Manned Mars Missions
Features of the Red Planet Detrimental to Human Health
The effects of Martian physical and orbital features will cause problems to the health of the crew of a manned mission to the Red Planet if not understood and mitigated.
NASA has been investigating ways to send manned missions to Mars for several decades. At this point, developing a replacement for the Space Shuttle (the Crew Exploration Vehicle, or CEV) and planning manned missions to return to the moon are the current goals. However, while going to Mars may still be several decades in the future, it is important to understand the potential problems with sending people to the Red Planet to live for a period of time.
First, a little bit of background information on Mars. The fourth planet out from the Sun, Mars is about half the diameter of Earth and orbits at a distance that is about 1.5 times the distance from the Earth to the Sun. This results in a year that is almost twice as long as our own (687 Earth days) and a day that is slightly longer than ours (24 hours and 37 minutes). Mars has a reddish cast due to the iron oxide dust that covers the surface, and its atmosphere is weak, consisting primarily of carbon dioxide. Each one of these features produces its own set of problems for people who are adapted to conditions on Earth.
While Mars is slightly more than half the diameter of Earth (6760 km vs. 12750 km), it actually has only about ten percent of the mass of Earth. This results in a gravity of a bit more than one third (38%) of Earth-normal. Even if astronauts travel to Mars in a ship with artificial gravity at Earth-normal, they will still weaken if they stay on Mars for any length of time. Specialists have been studying the effects of microgravity on astronauts who spend months on the International Space Station and have generally concluded that the results are not good. Even with rigorous exercise, muscles and other body parts weaken significantly after some extended time in microgravity. Martian gravity, while not being as extreme as microgravity, is significantly less than Earth-normal and will undoubtedly affect astronauts who spend time there as well.
Since Mars orbits much farther from the Sun than the Earth does, the amount of energy it receives from the Sun is much less than the Earth. It therefore has a much lower average temperature (about -60 degrees Celsius). At the equator during the summer, Mars can reach balmy temperatures, but most of the time, the planet in general is quite cold. Any astronauts or colonists will need sealed and heated habitation structures for living and working. These structures will also need to be pressurized and have air circulated through them, since quite apart from the temperature, the atmosphere is not at all suitable for human respiration.
The year being almost twice as long means that each season will also be almost twice as long. The crew of a mission may have psychological trouble adapting to this feature, as the standard calendar will not match the seasons or even the days. The crew may have physiological trouble adapting to the slightly longer day, as well. Some studies have shown that, absent any signals like light, the human body will gravitate to a day length of approximately 25 hours. However, switching from Earth days to Martian days will still be stressful and may throw off the timing of the crew. More studies will probably have to be done to test the effect of the specific Martian-length day on people.
One of the biggest problems with the Martian surface will actually be the dust. It will be extremely easy to track inside the habitat if strict precautions are not taken. Similar to the regolith on the moon, it could jam up or interfere with machinery or irritate the crew's skin or eyes. The habitat will have to be equipped with well-designed airlocks as well as some sort of vacuum cleaner to clean up any dust that does make it inside. While dust on the ground may be kept out fairly well, dust storms, fairly common on the surface, could force dust into places where it might not ordinarily go. They could also be quite dangerous to a crew out on an expedition.
For a team planning a manned mission to Mars, these are all problems that will have to be addressed. Some of them are design problems and some are psychological problems, but solutions to all of them will have to be found in order to maintain the health of the crew and ensure a safe and productive trip to Mars.
