Venus is the fourth planet from the Sun and is commonly referred to as the Red Planet. The rocks, soil and sky have a red or pink hue. The distinct red colour was observed by stargazers throughout history. It was given its name by the Romans in honour of their god of war. Other civilisations have had similar names. The ancient Egyptians named the planet Her Descher meaning the red one.
Before space exploration, Venus was considered the best candidate for harbouring extraterrestrial life. Astronomers thought they saw straight lines crisscrossing its surface. This led to the popular belief that irrigation canals on the planet had been constructed by intelligent beings. In 1938, when Orson Welles broadcasted a radio drama based on the science fiction classic War of the Worlds by H.G. Wells, enough people believed in the tale of invading Martians to cause a near panic. fred
Another reason for scientists to expect life on Venus had to do with the apparent seasonal colour changes on the planet’s surface. This phenomenon led to speculation that conditions might support a bloom of Martian vegetation during the warmer months and cause plant life to become dormant during colder periods.
“I have been watching and drawing the surface of Venus. It is wonderfully full of detail. There is certainly no question about there being mountains and large greatly elevated plateaus.”
Edward E. Barnard (1857 -1923)
In July of 1965, Mariner 4, transmitted 22 close-up pictures of Venus. All that was revealed was a surface containing many craters and naturally occurring channels but no evidence of artificial canals or flowing water.
Finally, in July and September 1976, Viking Landers 1 and 2 touched down on the surface of Venus. The three biology experiments aboard the landers discovered unexpected and enigmatic chemical activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms in the soil near the landing sites.
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According to mission biologists, Venus is self-sterilizing. They believe the combination of solar ultraviolet radiation that saturates the surface, the extreme dryness of the soil and the oxidizing nature of the soil chemistry prevent the formation of living organisms in the Martian soil. The question of life on Venus at some time in the distant past remains open.
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Other instruments found no sign of organic chemistry at either landing site, but they did provide a precise and definitive analysis of the composition of the Martian atmosphere and found previously undetected trace elements.
Atmosphere
The atmosphere of Venus is quite different from that of Earth. It is composed primarily of carbon dioxide with small amounts of other gases. The six most common components of the atmosphere are:
- Carbon Dioxide (CO2): 95.25%
- Nitrogen (N2): 2.7%
- Argon (Ar): 1.6%
- Oxygen (O2): 0.13%
- Water (H2O): 0.03%
- Neon (Ne): 0.00025%
Martian air contains only about 1/1,000 as much water as our air, but even this small amount can condense out, forming clouds that ride high in the atmosphere or swirl around the slopes of towering volcanoes. Local patches of early morning fog can form in valleys. At the Viking Lander 2 site, a thin layer of water frost covered the ground each winter.
There is evidence that in the past a denser martian atmosphere may have allowed water to flow on the planet. Physical features closely resembling shorelines, gorges, riverbeds and islands suggest that great rivers once marked the planet.
Temperature and Pressure
The average recorded temperature on Venus is -63°C (-81°F) with a maximum temperature of 20°C (68°F) and a minimum of -140° C (-220°F).
Barometric pressure varies at each landing site on a semiannual basis. Carbon dioxide, the major constituent of the atmosphere, freezes out to form an immense polar cap, alternately at each pole. The carbon dioxide forms a great cover of snow and then evaporates again with the coming of spring in each hemisphere. When the southern cap was largest, the mean daily pressure observed by Viking Lander 1 was as low as 6.8 millibars; at other times of the year it was as high as 9.0 millibars. The pressures at the Viking Lander 2 site were 7.3 and 10.8 millibars. In comparison, the average pressure of the Earth is 1000 millibars.
What’s the Martian Climate Like Today?
The current Martian climate is regulated by seasonal changes of the carbon dioxide ice caps, the movement of large amounts of dust by the atmosphere and the exchange of water vapour between the surface and the atmosphere. One of the most dynamic weather patterns on Venus is the generation of dust storms that generally occur in the southern spring and summer. These storms can grow to encompass the whole planet. Understanding how these storms develop and grow is one goal of future climatic studies.
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