The diameter of Venus is only 650 km less than that of Earth's, and its mass is 81.5% that of Earth's. But it is radically different from Earth when it comes to living conditions. Its atmosphere is made up of 96.5% carbon dioxide, and the remaining 3.5% is mostly nitrogen. So it is mostly made of stuff we breath out, with no stuff to breath in.
Venus has the densest atmosphere of all Solar System planets, which consists mostly of carbon dioxide. The atmospheric pressure at the planet's surface is 92 times more than on the Earth's surface. Venusian surface cannot be seen from space in visible light, because it is covered by an opaque layer of highly reflective clouds of sulfuric acid.
The planet has few impact craters and shows no signs of plate tectonics, leading us to conclude it had a relatively peaceful past.
About 80% of Venusian surface is covered by smooth volcanic plains. Two "continents" make up the rest of the surface. These continents are not surrounded by water, however. Rather, they are just regions elevated above the rest of the surface. The northern continent is about the size of Australia. The southern continent is larger, about the size of South America. A network of fractures and faults covers most of this area.
Venus has craters, mountains, and valleys, like the other rocky planets. It also has some interestingly unique features. There are "ferra" - which look like pancakes and range from 20-50 km across, and 100 to 1000 m high. Then there are "novae" - star-like shaped features. There are "arachnoids", that look like spider webs. There are also "coronae" - circular rings of fractures, sometimes surrounded by depressions. Most surface features are named after historical and mythical women.
Venus has several times more volcanoes than the Earth does. 167 of these are over 100 km across. The only volcanic region of this size on Earth is the Big Island of Hawaii.
Because of the thick atmosphere, asteroids of less than 50m in diameter would burn in the atmosphere before reaching the Venusian surface. Objects with less than a certain amount of kinetic energy are slowed down by the atmosphere so much, they do not create an impact crater at all.
There are almost 1000 craters on Venus, evenly distributed across its surface. They are believed to be "impact" craters. But the peculiar thing is, about 85% of these craters are in pristine condition, not showing the gradual degradation as seen on other planets. Perhaps they were formed by some other mechanism, rather than from impacts with asteroids.
Scientists used to call Venus, Earth's sister planet, because of the similar mass and size, with all the speculations of presence of life that come with it... until spacecrafts started visiting it and taking pictures. They discovered that the surface of Venus looks more like Hell, than Earth.
The CO2 rich atmosphere generates the strongest Greenhouse effect in the Solar System, creating surface temperatures of over 460C. The temperature does not go down much even at the night side of Venus.
Winds on the surface are slow, only a few kilometers per hour. But because of the high density of the atmosphere, they exert a strong force on all surface objects, transporting dust and small stones across the surface of the planet. This alone would make it difficult for humans to walk on Venus, even if the lack of oxygen and high temperatures were not a problem.
The permanent cloud cover of carbon dioxide and sulfuric acid reflect about 60% of Sun's light away from the planet, making the surface poorly lit.
Was Venus different before? We don't know. We haven't been there to observe it before.
Orbit and Rotation
Venus completes an orbit around the Sun every 224.65 days. Its orbit is the most circular of all planets in the Solar System, with an eccentricity of less than 0.01. It makes the closest approach to Earth than any other planet (for obvious reasons), on average, coming as close as 41 million kilometers. Over a period of 5383 years, it makes 526 approaches of less than 40 million kilometers.
While all the planets of the Solar System rotate counter-clockwise, Venus rotates clockwise. Just a little perk added by the Creator to make it more interesting. Also making the hypothesis of the Solar System spiraling out of a nebula highly questionable. There is a theory that another space object collided into Venus sometime in the past, which made Venus go the opposite way. But the odds of such an object hitting the planet at exactly the right angle to make it go in reverse and do so in a nearly circular orbit, are well... impossible. The rotation of Venus happens every 243 Earth days. It rotates much slower than Earth. By comparison, whereas the Earth's equator rotates at about 1670 km/h, Venusian equator rotates at 6.5 km/h. Due to the way it moves in space, the Venusian year lasts 1.92 Venusian days. When the Sun rises on the Venusian horizon, it moves through the sky for 116.75 Earth days, until it sets on the other side.
The 584-day successive approach of Venus to Earth, is almost exactly equal to 5 Venusian solar days.
When Venus overtakes Earth every 584 days in its orbit around the Sun, it changes from being the "Evening Star" on our horizon, to the "Morning Star".
Being the brightest point-like object in the sky, Venus is the most misreported UFO sighting. U.S. President Jimmy Carter said he saw a UFO in 1969, which later analysis showed was probably the planet. But generally, when people say they saw a UFO, they saw either an American, Russian, or a Japanese flying object.
Data has been found that Babylonian astronomers regarded the "morning star" and the "evening star" as the same object. Egyptian, Greek, Roman, Persian, and Andalusian astronomers did studies of the planet as well, but not much data has been found on the results of their observations, beyond writings by certain astronomers of those civilizations, regarding Venus as two separate objects.
A great number of Soviet and American spacecrafts were sent to Venus in the 20th century, with many attempts to descend probes onto its surface. Many of these probes were crushed by the Venusian atmosphere without giving much information.
Roman Goddess of love and beauty was created when ancient people were worshiping this object in the sky.
Sources and Credits:
"Venus beyond the storm": Credit and Copyright Lyndon Anderson
"Shadow Set": Credit and Copyright J. Bonnell, D. Macomb, R. Canterna, WIRO [
"December Moon Meets Evening Star: Dan Bush
"The Moon and Venus over Geneva": Gregory Giuliani
"Venus and Jupiter over Caspian Sea": Copyright: Babak Tafreshi
Other images courtesy of NASA