Density of Venus' atmosphere - historical

[PhilDSP]

Hello!

I'd like to know when the high density of the atmosphere of Venus was first determined or suspected. Was it with the Russian probes that the first evidence came that the atmosphere was much more dense than the Earth's? Or had there been other indications earlier in time that such was the case?

 

[Dr_Morbius]

http://lmgtfy.com/?q=atmosphere+of+venus

 

[PhilDSP]

I've been unable to find any published reference that anyone had suspected that the atmosphere of Venus differed substantially from the Earth's in density prior to 1967.

The Russian Venera 4 probe was the first to survive (partially) the entry into the atmosphere and take density measurements. It measured a density of about 22 Earth atmospheres but had a hull strength of only 25 atmospheres and was later found to be faulty. All of the early Venera probes that entered the atmosphere were eventually crushed by the atmospheric pressure.

http://en.wikipedia.org/wiki/Venera

Shortly afterward in 1967, data from the American Mariner 5 gave a calculation of 75 to 100 Earth atmospheres, far higher than had been expected.However, here is a very interesting and relevant site:

http://www.mentallandscape.com/V_Lavochkin1.htm

In 1967, most astrophysicists in America and Russia believed that Venus was extremely hot, but one MIT paper that year suggested the planet could be experiencing an Ice Age! Surface pressure on Venus was even more of a scientific guessing game at that time, with published estimates ranging from 3 to 1000 atmospheres. This uncertainty resulted from the inaccuracy of spectrographic methods, which measured conditions at the cloud tops, and from uncertainty about the depth of the atmosphere and the radius of the planet's hard surface. Estimates of 10 to 30 atmospheres of pressure at the surface were commonly believed.

That's a bit perplexing as the author earlier states that the barometer aboard Venera 4 had a range of 0.13-6.9 ± 0.2 atmospheres.