Question

Since Venus rotates so slowly, we might be tempted to conclude that Venus, like Mercury, keeps one face always toward the Sun. If this hypothesis were correct, we should expect that the dark side would be exceedingly cold. Pettit and Nicholson have measured the temperature of the dark side of Venus. They find that the temperature is not low, its value being only 29 degrees Fahrenheit, much warmer than our stratosphere in broad daylight. It is unlikely that atmospheric current from the bright side of Venus could perpetually heat the dark side. The planet must rotate fairly often to keep the dark side from cooling excessively.

What is the phenomenon being explained.?

Answer 1

The phenomenon being explained is the consistent high temperature across Venus's surface, including its dark side, despite its slow rotation. This is due to the thick atmosphere of Venus, predominantly composed of carbon dioxide, which creates an intense greenhouse effect, trapping heat and keeping the surface temperature uniformly high.

Step-by-step explanation:

The student is asking about the temperature distribution on Venus and why it does not exhibit extreme temperature differences between its day and night sides, despite its slow rotation. Venus has an atmosphere rich in carbon dioxide with a substantial greenhouse effect that maintains extremely high temperatures on the surface, exceeding 700 K (over 850 °F). This implies that even the dark side of Venus, which receives no direct sunlight, remains extremely hot due to the efficiency of this greenhouse effect in trapping heat within the atmosphere. The slow rotation of Venus, taking longer for one rotation than its orbit around the Sun, means that one side does not permanently face the sun as was once thought to be the case with Mercury. Nevertheless, due to the high capacity of the atmosphere to retain heat, even the night side retains high temperatures.

Moreover, the temperature being relatively consistent across the planet suggests that Venus undergoes rotation often enough to prevent one side from cooling too much, in contrast to the earlier belief that it keeps one face always toward the Sun like Mercury. This misnomer was clarified with advanced astronomical observations and an understanding of Venus's stringent atmospheric conditions.