Overview - page 3
Humans and Atmospheric Pressure
Atmospheric pressure is the amount of force exerted over a surface area, caused by the weight of air above it. Since fewer air molecules are present at higher elevations, atmospheric pressure decreases as altitude increases. The most common unit of measure for atmospheric pressure is the millibar (mb). On Earth, the average atmospheric pressure at sea level is 1,013 mb, while on Mars it is only 7.5 mb. At pressures lower than 700 mb, many humans become susceptible to altitude sickness, but they have also been known to survive conditions with much lower atmospheric pressure. For example, some climbers have reached the summit of Mount Everest, where the atmospheric pressure is only about 300 mb, without the aid of oxygen tanks. But they typically undergo a month-long period of acclimatization, during which time their bodies gradually become accustomed to the lower oxygen levels and atmospheric pressure. Despite this process, they are still unable to remain at the summit for very long. Because the atmospheric pressure on Mars is still much lower than even the summit of Mount Everest, astronauts visiting Mars would require pressurized spacesuits to venture out into the Martian environment.
Global Dust Storms on Mars
Because of Mars' low atmospheric pressure, visitors there would need to wear a pressurized space suit. This one is called an extravehicular mobility unit (EMU) and consists of three major components: (1) the upper torso, (2) the lower torso, and (3) the portable life-support system. (Image Credit: NASA)
The Mars Orbiter Camera onboard the Mars Global Surveyor captured these two images in June and July 2001. The view from June shows the Tharsis volcanic region (left), Valles Marineris chasms (right), and the late winter south polar cap (bottom). The view from July shows the same regions, but most of the details are hidden by a global dust storm that enshrouded nearly the entire planet. (Image Credit: NASA/JPL/Malin Space Science Systems)