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Venus, Earth’s Sister Planet

What’s Up? by Adam England


After the moon, the second-brightest object in the night sky is the planet Venus.

Mariner 10 flyby 2 February 1974, image courtesy NASA

Records going back at least 5,000 years show human societies acknowledging that the “morning star” and “evening star” were one and the same, traveling horizon-to-horizon as it circles the sun.


The Sumerians associated Venus with the goddess Inanna, their only deity who could traverse from the netherworld and back to the heavens. The Mayan calendar focuses on the movements of three celestial bodies, the sun, moon and Venus. Many Eastern cultures refer to Venus using literal translations of“metal star,” referencing the importance they place on it as one of the five elements.


With advancements in visual astronomy, we learned that Venus was a terrestrial planet with thick cloud cover, rendering direct observation of its landscape impossible.While the early space race saw the US aim for the moon and Mars, the Soviet Union focused on the inner solar system, successfully exploring the planet with dozens of flybys, orbiters, landers and even the first off-earth balloons. All this data, as well as continuing missions and discoveries, told us that Venus was very similar to Earth in many ways, and radically different in others.


At about 90% the size of Earth, it is the closest in size of any planet or exoplanet we have yet discovered. Venus orbits the sun at about ¾ the distance Earth does, but rotates very slowly, completing a revolution once every 243 days. Due to its runaway greenhouse effect, Venus also has the densest atmosphere of all the rocky planets. The air pressure on the surface is equivalent to 92 times sea-level pressure on Earth, or about the same as 3,000 feet underwater. Clouds of sulfuric acid hold in the sun’s heat, and surface temperature averages above 867°F. By any calculation Venus is a desolate, inhospitable landscape of volcanic activity, an example of what Earth could be like in a few million or billion years.


Recently scientists used extremely powerful telescopes on Earth to analyze the Venusian atmosphere, detecting the chemical phosphine at 20 parts per billion. While phosphine can result from natural chemical processes, it is only known to appear in such quantities from organic processes. Without diving into a deep chemistry lesson, suffice to say that we have no explanation of how the phosphine would be there except production by an active anaerobic ecosystem, as in fermentation and deepsea organisms on Earth.


To catch a glimpse of our cosmic neighbor/twin during the month of October, look to the east in the hours before sunrise for the bright “Morning Star.



Adam England is a local insurance broker and small-business consultant who moonlights as an amateur astronomer, writer, and interplanetary conquest advisor. @Follow his rants and exploits on Twitter@AZSalesman or Facebook. com/AdamEfromAZ.


To learn more about the sky, telescopes, or socialize with other amateur astronomers, visit us at prescottastronomyclub. org or Facebook @PrescottAstronomyClub to findthe next star party, StarTalk, or event.


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