CHAPTER 10 THE NEW LOOK OF VENUS

The historic mission of Mariner II to the near-vicinity of Venus and beyond has enabled scientists to revise many of their concepts of interplanetary space and the planet Venus.

The composite picture, taken from the six experiments aboard the spacecraft and the data from the DSIF radar experiments of 1961 and 1962 revealed the following:

Interplanetary space between the Earth and Venus, at least as it was during the four months of Mariner’s mission, had a cosmic dust density some ten-thousand times lower than the region immediately surrounding the Earth.

During this period, the extremely tenuous, widely fluctuating solar winds streamed continually out from the Sun, at velocities ranging from 200 to 500 miles per second.

An astronaut travelling through these regions in the last quarter of 1962 would not have been seriously affected by the cosmic and high-energy radiation from space and the Sun. He could easily have survived many times the amount of radiation detected by Mariner’s instruments.

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The astronomical unit, as determined by radar, the yardstick of our solar system, stands at 92,956,200, plus or minus 300 miles.

The mass of Venus in relation to the Earth’s is 0.81485, with an error probability of 0.015%.

The rotation rate of Venus is quite slow and is now estimated as equal to 230 Earth days, plus or minus 40 to 50 days. The rotation might be retrograde, clockwise with respect to a Sun-facing reference, with the Sun rising in the west and setting in the east approximately one Venusian year later. The planet seems to remain nearly star-fixed rather than permanently oriented with one face to the Sun.

Venus has no magnetic field discernible at the 21,598-mile approach of Mariner II and at that altitude there were no regions of trapped high-energy particles or radiation belts, as there are near the Earth.

The clouds of Venus are about 15 miles thick, extending from a base 45 miles above the surface to a top altitude of about 60 miles.

At the resolution of the Mariner II infrared radiometer, there were no apparent breaks in the cloud cover. Cloud-top temperature readings are about minus 30 degrees F near the center (along the terminator), and ranging down to minus 60 degrees to minus 70 degrees F at the limbs, showing an apparent limb-darkening effect, which would indicate a hot surface and the absence of a supercharged ionosphere.

A spot 20 degrees F colder than the surrounding area exists along the terminator in the southern hemisphere: a high mountain could exist in this region, but such an hypothesis is purely conjectural. A bright radar reflection is also found on the Equator in the same general region. Causes of these phenomena are not established.

At their base, the clouds are about 200 degrees F and probably are comprised of condensed hydrocarbons held in oily suspension. Below the clouds, the atmosphere must be heavily charged with carbon dioxide, may contain slight traces of oxygen, and probably has a strong concentration of nitrogen.

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As determined by the microwave radiometer, Venus’ surface temperature averages approximately 800 degrees F on both light and dark sides of the planet. Some roughness is indicated and the surface reflectivity is equivalent to that of dust and sand. No water could be present at the surface but there is some possibility of small lakes of molten metal of one type or another.

Some reddish sunlight, in the filterable infrared spectrum, may find its way through the 15-mile-thick cloud cover, but the surface is probably very bleak.

The heavy, dense atmosphere creates a surface pressure of some twenty times that found on the Earth, or equal to about 600 inches of mercury.

The mission was completed and the spacecraft had gone into an endless orbit around the Sun. But before Mariner II lost its sing-song voice, it produced 13 million data words of computer space lyrics to accompany the music of the spheres.

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