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.

—111

—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.

—112

—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.