Facts about Venus

The planet Venus is a fascinating place.    It is the 2nd planet from the Sun and it has an incredibly high temperature at its surface, about 900 degrees Fahrenheit.   This is due to the blanketing effect of the atmosphere which acts like a greenhouse, trapping in the heat from the Sun and creating a hothouse planet.    The atmosphere is mostly carbon dioxide at very high pressures, about 10 times greater than Earth's atmosphere at surface level.  The atmosphere also contains sulfuric acid (H₂SO₄)  as well as other acids such as hydroflouric acid (HF) which are extremely corrosive materials.  The few spacecraft sent to land on Venus have been subject to rapid corrosion and crushing pressures.  Suffice it to say, Venus is not the kind of planet that humans could land on and visit.

Venus has been visited by numerous spacecraft in the last 40 years.    The first spacecraft to visit Venus was Mariner 2, which flew by in 1962.   This was the first spacecraft to visit another planet in our solar system.   The Soviet Union sent many spacecraft to Venus.  Some were orbiters and some were landers.  The Soviet Venera series of landers took the first and only pictures of the Venusian surface.  They showed melted rocks on the surface in a gloomy, hazy atmosphere.  The United States landed 4 probes on Venus in 1978.    These were 1 large and 3 small atmospheric probes that were carried to the planet by the Pioneer Venus mission.   The Pioneer Venus orbiter then released the probes which landed on 4 different spots on the planet and took measurements.

Mariner 2 spacecraft

  Pioneer Venus mission

The 3 small probes were called the North probe, Day probe and Night probe, depending on where they landed on the surface.   They took measurements of the atmosphere as they parachuted down to the surface.   Their instruments measured temperature and pressure as well as 'dustiness' and radiative characteristics of the atmosphere.   They also studied winds and meteorology.

The Atmospheric Structure experiment gave pressure, temperature and wind information.  The Nephelometer experiment had a bright light which was shining on the cloud particles as the probe came down through the atmosphere and measured energy backscattered from these particles to determine their size and shape and at what altitudes the cloud layers were located.  The Net Flux Radiometer experiment determined at what altitudes energy from the Sun is deposited into the atmosphere.

These instruments were on the small probes.   The Large probe also had the Nephelometer experiment and Atmospheric Structure experiment.  But it had more experiments than the small probes.   There was also a Gas Chromatograph experiment which determined the chemical composition of the atmosphere.  Also, there was an Infrared radiometer experiment which determined where the cloud layers were, what they were made of, and if there was water vapor in the layers.  In addition, there was a Solar Flux radiometer on the Large Probe which measured how far down the solar energy reaches into the atmosphere.

The chemistry of Venus' atmosphere is quite interesting: sulfuric acid droplets interacting with surface minerals and creating some exotic chemical species not seen in Earth's atmosphere.  Other sulfur species exist there as well, including COS and H2S.

The planet rotates on its axis at a leisurely pace (it takes 243 days to rotate once with respect to the background stars, whereas Earth rotates on its axis in ~ 24  hours (the length of our day). Though the planet rotates slowly, the atmosphere is a whirlwind of activity.   Venus has the so-called "4-day rotation" of its upper atmosphere, where the clouds circulate around the planet very quickly.  The details in the clouds can be seen in the following image.   Ultraviolet images of the atmosphere show the detail in the clouds, whereas in visible light (and in the telescope), Venus is a featureless ball.

False-color image of Venus,

showing detail in the clouds and circulation patterns from UV data

 *more to come *

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photos:  NASA