"How's the Weather?"-Not a Good Question on MarsBy Hugh Ross When enthusiasts for Martian life and Martian colonization speak of Mars's "favorable surface conditions," we must ask, "'favorable' compared to what?" Pathfinder confirms our suspicions and suggests that conditions may be worse than we imagined. Typical surface temperatures on Mars are much colder than Earth's south pole in winter. The equatorial zones, though, have been known to reach summer peaks of a sizzling 45ºF (7ºC),(1) definitely survivable, if not comfortable. However, one slight problem receives little attention: the problem of atmosphere. The Martian atmosphere is so thin that Mars's surface air pressure is only 0.6% of Earth's.(2) That low pressure means severe temperature drops from day to night and from ground level to a few feet above ground level. The Viking landings of the 1970's verified day-to-night surface temperature differences of 180ºF (100ºC).(3) Similar temperature differences would occur between areas of shade and sunlight. What the Vikings couldn't measure, Pathfinder could and did.(4) With a five-foot "mast" sporting thermocouples and windsocks at different heights, Pathfinder beamed back this data: the top of the mast was 70ºF(40ºC) colder than the bottom.(5) Pathfinder also reported rapid temperature fluctuations, more than 40ºF (20ºC) up or down in just a few minutes. These temperature differences represent the Martian ideal. Pathfinder landed in a protected valley, Ares Vallis, and took measurements during the Martian spring. In another year will come the Martian autumn with its 200-mile-per-hour dust storms-much worse than the one the movie Rocketman depicted. Pathfinder's rover found rocks severely sandblasted and some gouged with grooves from such storms.(6)
Then there's the water problem to consider. While Mars does have a functioning water cycle, the quantity of water in the Martian atmosphere is less than one ten-thousandth what exists on Earth.(8) And that small amount of water never gets a chance to precipitate. Because Mars air pressure is so low, ice never melts and water vapor never liquefies. The effect is the same as boiling water at high altitudes. On top of Pikes Peak in Colorado, where the air pressure is but half that at sea level, water boils at 175ºF (80ºC). Eventually, as air pressure decreases, water boils at its freezing point. It goes from ice to vapor, skipping the liquid stage. A few species of microbial life might be able to survive such conditions by hibernating in a cocoon. However, critical life stages that make such hibernation possible could not be carried out on Mars. For this reason I conclude that any life found on Mars must have been carried there from Earth.(9) As for protecting future astronauts on Mars, we'll need some remarkable space suits to handle the 70ºF to 80ºF (45ºC+) temperature difference between feet and head and the fluctuations from moment to moment. We must also find ways to deal with powerful wind gusts hitting suddenly and at different heights from the surface at different times. We must guard against punctures and protect against radiation. I'm inclined to agree with those who say we must forget about suits and think about heavily shielded shelters and vehicles. References:
1. Michael H. Carr, Water on Mars (New York: Oxford
University Press, 1996), p. 13.
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If these conditions seem harsh, consider what the Mars Global Surveyor
discovered. Launched a few weeks before Pathfinder and arriving a few weeks
later, Surveyor made the first-ever measurements of Mars's magnetic field.
It is only about a tenth of a percent as strong as Earth's; thus, it has
virtually no ability to protect against solar and cosmic radiation.(7).
(See article on 
