MadSci Network: Astronomy
Query:

Re: Is the temperature on Venus cooler than mercury at anytime?

Date: Fri Mar 26 10:02:31 2004
Posted By: Carolyn Ernst, Grad student, Planetary Geology
Area of science: Astronomy
ID: 1079105072.As
Message:

The daytime surface temperature on Mercury can be as high as ~720 K (447 deg. C / 837 deg. F), and the nighttime temperature can be as low as ~90 K (-183 deg. C / -297 deg. F). The average temperature is ~440 K (167 deg. C / 333 deg. F). Mercury is so hot on the day side because it is so close to the sun, and it is so cold on the night side because it has no significant atmosphere to provide insulation from the cold temperature of space.

The daytime surface temperature on Venus can be as high as ~740 K (467 deg. C / 873 deg. F). The high surface temperature of Venus is due to the greenhouse effect. Check out this previous MadSci answer and this website for more information about the greenhouse effect on Venus. Venus's atmospheric pressure is 90 times larger than that of Earth, and it's composed mostly of carbon dioxide. Venus is ~500 K warmer than it would be if its atmosphere were transparent to infrared light (heat). The average surface temperature on Venus is ~730 K (457 deg. C / 855 deg. F). The temperature is very constant over the whole surface (the temperature at all locations is within ~10 K of everywhere else). This is due to the insulation of the atmosphere. At its hottest, Mercury is not quite as hot as Venus, but their temperatures are very similar.

Humans could not live on either Mercury or Venus without major forms of shelter. Mercury has essentially no atmosphere, so humans would not have any oxygen to breathe. The pressure is so low that it is a vacuum environment in which humans could not survive without a space suit. The temperatures are also too extreme for human survival.

The atmospheric pressure on Venus is much too large for humans. Its temperature is hot enough to melt lead, which is much to hot for human survival (and much too hot for most materials, too). Several Venera landers (sent to Venus by the Soviet Union beginning in 1975) survived for about an hour and transmitted data back to Earth before failing due to the high pressure and temperature. Finally, even if its atmospheric pressure and temperature were not so extreme, the air is made up mostly of carbon dioxide, which is toxic to humans.


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