Earthbound Observations of the Planet Venus

Visually, Venus has been known for thousands of years, appearing as one of the brightest objects in the night sky. Images from Earthbound telescopes show its varied phases, which were first noted by Galileo and were one of the key arguments for a heliocentric solar system.

The covering of Venus is unseen from Earth due to full, cloud cover; the atmosphere of Venus being discovered in the eighteenth century and subsequently found to consist generally of carbon dioxide. The clouds were also considered by spectroscopy (measuring the spectrum of the light from the planet) to include sulphuric acid droplets, hence being very corrosive. In 1924, bolometry (measurement of infrared radiation) indicated that the cloud tops had a climatic characteristic of about -43 degrees Celsius. Also wind speeds measured by cloud motions were recorded at 220 miles per hour. In 1956, radio astronomy enabled measurement of the climatic characteristic of the covering of Venus, which was found to be 327 degrees Celsius, but as far as Earth based observations went at this time, this was about all we could learn about the planet.

Telescope

Then in the early 1960's, the radio telescope at Goldstone in California revealed that Venus had a 243 day retrograde rotation; in other words it orbits counter-clockwise colse to the Sun, but rotates itself in a clockwise direction. It is the only terrestrial planet to exhibit such behaviour. The retrograde Venusian day is so long that it is assuredly longer than its year (224.7 days) and may be a considerable factor in Venus having practically no magnetic field. Despite this, Venus does have an ionosphere close to its surface, but whereas the ionosphere of the Earth is due to its intrinsic magnetic field, the ionosphere on Venus is due to interactions of the solar wind.

In the early 1970s, the Goldstone telescope also made radio images of the covering of Venus and varied features were identified. Although the radar images had poor resolution, they did communicate light areas of rough terrain and darker regions of flat plains.

Earthbound Observations of the Planet Venus

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