Tuesday, February 8, 2022

  -  3453  -  VENUS  -  our sister planet?   The planets are all idiosyncratic because of the different ways they were put together.  The tumultuous and random nature of the process was not fully appreciated for a long time.  


-------------  3453  -     VENUS  -  our sister planet?

-  A space probe reached Venus in April, 2006.   It takes 163 days to reach our sister planet, the second rock from the Sun.  Venus is the third brightest object in the Sky following the Sun and the Moon.  It is also called the evening star and the morning star.


-    We call it our sister planet because it is so close, formed at the same time and about the same size.  Venus diameter is 7,521 miles, Earth is 7,926 miles, a difference barely the distance from San Francisco to Los Angeles.  Venus is 5 *10^24 kilograms and Earth is 6*10^24 Kilograms, 81.5% the mass of the Earth.  

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--------------------- Venus 4.869*10^24 kg.               Earth 5.974 kg.

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-  But Venus is different:   Venus has no moons.  It has on magnetic field. It has an iron core but rotates too slowly to generate magnetic fields.  It has no plate tectonics.  Its atmosphere is so full of carbon dioxide (96%) that a  greenhouse effect*  raises the average surface temperature to 850 degrees Fahrenheit.  This is hot enough to melt lead.  

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-  No wonder it is difficult to land a scientific probe on Venus.  The CO2 gases were originally vented by early active volcanoes.  Venus had no ocean water to dissolve the CO2 so it remains in the atmosphere to this day.

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-  *  “Greenhouse effect“: Short wavelength visible light is able to penetrate the thick carbon dioxide atmosphere but the radiation from the warm surface is at a longer wavelength and it becomes absorbed by the carbon dioxide trapping the heat under a blanket that eventually heats the surface to over 850 Fahrenheit.  CO2 is transparent to visible light but opaque to infrared radiation.

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-  Venus spins on its axis the opposite direction as the other planets.  And, it spins slowly, taking 243 days to rotate.  It takes 225 days to complete one orbit around the sun.  So a Venus day is about the same as a Venus year, although a day is a little longer.  

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-  This 243 rotation day is called a “sidereal rotation period“, to reach the same spot in the sky.  The solar rotation period standing on the surface of Venus is 116.8 days.  That is a long time to wait for a sunrise, and be looking west, because the sun rises in the west on Venus not in the East.

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-  Venus is tilted 177 degrees, just 3 degrees from perpendicular to the plane of its orbit, so it has no seasons.  It is simply a hot cloudy day everywhere and does not cool down even at night.  It is speculated that this unusual tilt and retro rotation was caused by a monumental impact early in the planets existence.  Similar to the impact on early Earth that formed our Moon.

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-  The Venus heavy atmosphere creates crushing surface pressure, 90 times heavier than that of Earth (1,296 pounds/inch^2).  It is equivalent to 3,000 feet deep in the ocean, twice what submarine crush depth is considered, 1,500 feet below the waves.

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-  The clouds in the atmosphere are sulfuric acid. They are yellow-orange in color and reflect 65% of the sunlight back into space (the albedo).  The winds are hurricane force rotating completely around the planet in 4 days. 

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-   The winds create the only erosion on the surface since there is no water to cause erosion, so erosion is minimal.  Yet there are few craters indicating that the geologically active surface has renewed itself throughout much of Venus history.

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-  Our first pictures of the Venus surface came from the Soviet spacecraft that landed in 1981.  It found the Venusian’s rock to be similar to the lava rocks called basalt found on Earth, and in my back yard.

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-  The NASA Magellan spacecraft circled Venus in 1990 with radar images mapping over 98% of its surface having a resolution to 75 meters (you could resolve a football field if there was one).  It was 4 years in orbit then was intentionally crashed into the planet’s surface in 1994. 

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-   Radar observations of the planet Venus in the 1970s proved that light slowed down as it moved past the Sun’s gravitational field, confirming Einstein’s general relativity equations.

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-   Magellan revealed the diverse volcanic features and flows on the surface.   It mapped the longest channel known in the solar system.  It identified two continents on the planet:

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------------------- One the size of Australia called “Ishtar Terra” with a mountain rising 6.8 miles above the plain ( Mount Everest is 5.6 miles high). 

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------------------ The second continent is called Aphrodite Terra and is half the size of Africa, 10,000 miles by 12,000 miles.

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-  The planets are all idiosyncratic because of the different ways they were put together.  The tumultuous and random nature of the process was not fully appreciated for a long time.  Now our planetary probes have brought new insights into our solar system’s amazing birth.  It seems that everything we learn is not what we expected.  That is what makes discovery so challenging and so adventurous.  Learning is its own reward.

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February 8, 2022      -     VENUS  -  our sister planet.              587    3453                                                                                                                                               

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-----------------------------  Tuesday, February 8, 2022  ---------------------------






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