200-Degree Variation In Day-Night Temperatures On Venus Detected

New information about the planet Venus including a temperature variation of some 200 degrees between day and night, has been revealed here by Prof. Fred T. Haddock of the University’s astronomy and electrical engineering departments, director of the Peach Mountain Radio Astronomy Observatory near Dexter.

Maximum surface temperatures of Venus has been determined by U-M scientists to be near 800 degrees.

A project conducted at the observatory by John R. Dickels, a U-M graduate student working under the direction of Haddock, has resulted in the first determination of temperature variation between day and night on Venus from near and far observations.

Workers at the U.S. Naval Research Laboratory in Washington, D.C., the National Radio Astronomy Observatory at Green Bank W.V., and in Russia, however, have previously noticed temperature variations from measurements of evening and nighttime temperatures when Venus is nearest the earth.

But the U-M observations, which have been the most extensive of any in the world on that planet, according to Haddock, included numerous measurements when Venus showed its full daytime side from the far side of the sun at its greatest distance from the earth.

Observations are extremely difficult to make when Venus is on the far side of the sun, not only because the signal from the planet is weakened by the great distance but also, the sun, which is a strong radio emitter, interferes with the planetary radiation, Haddock said.

The careful measurements of this temperature variation has allowed the scientists to determine the properties of the surface of Venus, he pointed out.

It has been determined that the atmosphere of that planet is several times denser than the earths’ and the temperature, as revealed by the U-M observations is much hotter.

Also, there is no water on the surface of Venus because of the high temperature and possibly not as much in the atmosphere as in the earth’s atmosphere. The clouds are largely oxides of carbon with some water vapor in them.

Optical telescopes have previously indicated the temperature for Venus of about 25 degrees below zero. This discrepancy is accounted for by the fact that optical telescopes only see the outer edge of the dense layer of clouds which surround that planet. At radio frequencies, however, the telescope (radio telescope) can see through the cloud layer to the actual surface of the planet, Dickel and Haddock report.

The great difference in temperature between the solid surface and the cloud tops is accounted for the “greenhouse effect” of the dense clouds which keep the enclosed area warmer than the outside air.