Mohawk Valley Astronomical Society

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Venus Fun Facts

by Perry Pezzolanella

The “Year of Venus” articles dedicated to its history, future, current knowledge, and exploration is almost complete. The best way to end the year is with a thorough roundup of facts and figures that will make everyone a pro when talking about Venus.

Venus is the second planet from the Sun. It orbits the Sun at an average distance of 67.2 million miles and can get as close as 66.7 million and as far as 67.7 million miles. The variation of hardly a million miles makes the orbit almost perfectly round compared to the other planets. Venus orbits the Sun once every 224.7 Earth days at an average speed of 78,341 miles per hour. Venus takes 243 days to rotate once on its axis. This means that Venus travels around the Sun faster than it rotates. This odd combination means that the time from noon to noon on the surface takes 117 days. Venus rotates backwards on its axis for reasons unknown, therefore the Sun rises in the west and sets in the east. The time from sunrise to sunset is 58.5 days. The extremely dense atmosphere and slow rotation makes for long twilights lasting up to two weeks.

Venus can come as close as 24.7 million miles to Earth and shine as bright as magnitude -5. That is bright enough to cast faint shadows under ideal conditions. Because Venus orbits closer to the Sun than Earth it can go through a complete set of phases from full to crescent in the evening and then from crescent to full in the morning. Venus can rarely transit the Sun as seen from Earth as it last did on June 5, 2012, but not visible again until December 11, 2117. It is also the only planet that can exceed one arcminute in size in the sky. When it is that large it is always a razor thin crescent hardly a few percent illuminated. Keen vision of 20/15 or better may make it possible to see such a large crescent with no optical aid.

The Romans knew of seven bright objects in the sky: the Sun, the Moon, and the five brightest planets; Mercury, Venus, Mars, Jupiter, and Saturn. They named the planets after important gods, but Venus, being the brightest, was named after the Roman goddess of love and beauty.

Venus is often referred to as Earth’s twin, but only in size and composition. Venus is 7520 miles in diameter and Earth is 7920 miles. Gravity on Venus is 91% Earth; therefore a 150-pound person on Earth would weigh 137 pounds on Venus. Venus is classified as a terrestrial planet along with Mercury, Earth, and Mars which means it has a solid surface one can stand on.

Venus has no moon and no magnetic field but has a faint greenish glow high in its atmosphere caused by the excitation of oxygen from the Sun’s radiation, but not a true aurora. This is not to be confused with the Ashen Light which is a faint reddish-brown glow on the night side. This may be caused from the intensely hot surface of nearly 900ºF shining faintly through the clouds, but more investigation is needed as this remains a classic Venus mystery.

Venus has over 1600 major volcanoes along with over 100,000 smaller ones that include fumaroles and vents. Most of the larger volcanoes are shield volcanoes and the surface is covered in an expansive flow field. It is suspected that a vast volcanic upheaval resurfaced most of the planet around 700 million years ago. Venus has a very young surface with very few impact craters. The huge amounts of carbon dioxide and sulfur dioxide released from so many volcanoes may have destroyed the climate. Venus may have had an ocean with a tropical Earth-like climate, but now it is a desiccated, pressurized inferno. Venus only has around 900 craters and most are over a mile across. The dense atmosphere destroys most meteors before reaching the surface with only the largest surviving. There are very few dune fields mainly due to the lack of large amounts of sand and dust, and sluggish winds.

Venus has an atmosphere that packs a lethal punch. It is composed of 96.5% carbon dioxide, with the rest being nitrogen, along with traces of other gases including sulfur dioxide. Sulfuric acid in the clouds dominates and can combine with hydrogen and fluorine to create a mineral acid capable of dissolving almost anything. The atmospheric pressure at the surface is around 92 times Earth’s, equivalent to being 3000 feet beneath the ocean. The pressure is high enough that carbon dioxide behaves like a supercritical fluid that covers the entire surface and is very efficient in transferring heat. Night is as hot as day and the poles are no cooler. The average surface temperature is 870ºF. The Sun as seen from Venus is about 1.5 times larger than seen from Earth. The clouds can thin enough where the Sun might shine briefly at the surface and some photos of rocks casting shadows from landers seem visible. The intense pressure gives the sunlight a deep orange cast at the surface. Higher up where the air is thinner the sunlight becomes less orange and has more of a yellowish cast. Death on Venus would take only one second since it would come from four causes all at once; one would be suffocated, crushed, burned, and dissolved.

The clouds are the dominating feature of Venus. They are high, thick, and composed of three layers. The base of the cloud deck is about 30 miles above the surface and there are thin areas and convective areas within the 20-mile layer above. There may be lightning within the clouds and ash plumes from erupting volcanoes. The entire cloud deck is whipped by winds as strong as 220 miles per hour and takes about four days to rotate once around. Winds at the surface are about 3 miles per hour and behave more like a current in the thick atmosphere. The towering mountains and volcanoes on Venus create ripples in the clouds that are visible from orbiting spacecraft. There is a layer within the clouds that is almost Earth-like with similar atmospheric pressure and temperatures around 70ºF, although the air is mostly carbon dioxide laced with sulfuric acid.

Elevation is the only way to escape the heat and pressure. The highest point on Venus is Maxwell Montes at 37,000 feet, higher than Everest, with an air pressure only 44 times Earth’s and a refreshing 680ºF. The pressure may be cut in half, but the heat remains relentless. The deepest point on Venus is Diana Chasma, nearly 2 miles deep, which most likely has the worst air pressure on Venus, about 105 times Earth’s, and a temperature approaching 1000ºF. The places with worse temperature are near suspected active volcanoes where orbiting spacecraft have detected temperatures as high as 1300ºF. Here, lead, tin, and zinc will melt on the surface and compounds such as lead sulfide and bismuth sulfide vaporize, which later condense as frost on the cooler mountain peaks.

Ten spacecraft have successfully landed on Venus, all from the former Soviet Union from 1970-85: Venera 7-14, and Vega 1&2. Venera 7 was the first spacecraft to land on another planet and transmit data on December 15, 1970. Venera 9 was the first spacecraft to transmit a photo from the surface of another planet on October 22, 1975. Venera 13 and 14 remains the only spacecraft to transmit color photos from the surface of Venus in March 1982. The Soviets also are the first to deploy balloons into the clouds from the Vega 1&2 spacecraft, which survived for up to 46 hours. One of the probes from the U.S. Venus Multiprobe mission unexpectedly survived a hard landing and transmitted data for 67 minutes. The longest lasting lander, Venera 13, survived for 127 minutes, all others barely survived an hour in the hostile conditions varying from air pressures of 87 to 94 atmospheres and temperatures of 855ºF to 905ºF.

The former Soviet Union, U.S (NASA/JPL), Europe (ESA), and Japan (JAXA) are the only countries/agencies to have explored Venus. China and India plan to do so by 2030. Most missions have been flybys and orbiters. Venus was the first planet visited by a spacecraft when Mariner 2 flew by on December 14, 1962. The exploration of Venus is kicking into high gear for the 2030s with VERITAS, DAVINCI, and EnVision approved and slated for launch. The list of fun and frightening facts will only grow longer as our knowledge of Venus increases.