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Odd Planet: The Weirdness of Venus

By Edited Nov 20, 2016 5 2
Planet Venus
Credit: NASA public domain image.

Venus without clouds, an image generated with radar by NASA's Magellan spacecraft.

Facts about Venus, the closest planet to Earth

The closest planet to Earth[1] is often said to be the most like Earth of any of the other planets in our solar system. This is true, although Venus is very strange, and very different from Earth in many ways.

Planet Earth is located about 93 million miles (150 million kilometers) from the sun. The distance varies slightly over the course of its orbit.[2]

Planet Venus, one of two planets closer to the sun than we are, is about 67 million miles (108 million kilometers) from the sun.[1] This means that at the closest, Earth and Venus are about 26 million miles (41 million kilometers) apart.

Compare this with Mars, for which we like to discuss the possibilities of sending human beings there. It is located about 142 million miles (228 million kilometers) from the sun,[3] so at the closest, the red planet is about 49 million miles (78 million kilometers) away from us.

What do all these numbers mean? It means Mars is nearly twice as far from Earth as Venus is, thus removing whatever doubts you had that Venus is the closest planet to Earth.

Viewing Venus from Earth

Venus Viewed From Earth
Credit: Wikipedia photo by Brocken Inaglory, CC BY-SA 3.0.

Venus is the brightest object commonly seen in the night sky, after the moon.[1]

After the moon, which shows as a full moon every 29.5 days, the next-brightest object commonly seen in the night sky is Venus. When it is visible, it is noticeably much brighter than all stars in the sky.[1]

The orbits of Venus and Earth are not the same length of time, with an Earth year being about 365.25 days, and a full orbit for Venus taking about 224.7 days. The planet catches up with Earth about every 584 days. For nearly half this time, our neighbor planet is called a “morning star,” being highly visible before sunrise. For a similar length of time, the planet switches to being an “evening star,” being highly visible after sunset.[1]

Viewed through a telescope, the planet goes through phases like the moon does, disappearing for part of the time, and appearing as a crescent shape – although it only appears full when on the other side of the sun from where we are, and thus not visible.[1]

Phases of Venus in relation to Earth

Phases of Venus
Credit: NASA public domain image.

When Venus is on the "left" side, it is seen as a morning star, seen in the east before the sun rises. When it is full, in the center, we can't see it at all because the sun is in the way. When it is on the "right" side, it is seen as an evening star, seen in the west after the sun sets.

Venus has no moons and spins backward

Venus Rotation
Credit: Created by me from two public domain NASA images.

Venus doesn’t have any moons, and neither does Mercury. Earth of course has one, and all other planets have two or more. Even several of the dwarf planets, such as Pluto, Haumea, and Eris, are known to have moons.[4]

It is thought that Venus likely had a moon long ago, although something happened. The planet was struck by some sort of large object, sufficiently powerful to actually cause it to spin in the opposite direction.[1]

If you were to look down on the solar system from above Earth’s North Pole, all planets are orbiting in the same direction around the sun, counter-clockwise. And all planets except for two are spinning counter-clockwise as well.[5]

The planet Uranus spins on its side. Venus spins backward, or what would appear as clockwise, as a result of the mysterious huge collision that occurred billions of years ago.[5][1]

What this did was cause the moon that was circling Venus to be sucked into the planet, crashing in what must have been another incredible impact.[1] A lot of the planets took a serious beating earlier in our solar system’s existence, including Earth.

The Venusian atmosphere and landscape

Surface of Venus
Credit: Public domain courtesy of NASA.

The surface of planet Venus.

The diameter of Venus is 95% that of Earth, making the planet very close to the same size as our own.[1] Due to the planet having slightly less mass compared to Earth, there is slightly less gravity as well. Take your weight here on Earth and multiple by 0.907 to see what you would weigh on Venus.[1]

Like Earth, it is a rocky planet. The first four planets closest to the sun have this characteristic, and the four larger ones further away have no rocky surface but are literally huge balls of gas, hence the term “gas giants.”[6]

The atmosphere of Venus is about 96.5% carbon dioxide, compared with Earth’s 0.04%. The rest of the Venusian atmosphere is mostly nitrogen.[1]

About 80% of the planet’s surface is lava flows, and the planet has several times as many volcanoes as Earth, including many that are very large, with the only active volcano on Earth of comparable size being Mauna Loa, which comprises most of the Big Island of Hawaii.[1]

Venus has many impact craters from asteroids, although none smaller than about 3 km (2 miles) in diameter. This is because the thick atmosphere causes any smaller than about 50 meters (170 feet) in diameter to burn up before reaching the planet’s surface.[1]

The planet does not have tectonic plates like Earth. Earth is the only planet with tectonic plates in our solar system, although it’s possible that one or more of the large moons of Jupiter or Saturn feature tectonic plates.[1]

Compared with Earth, the planet has a very weak magnetic field. Earth’s magnetic field is generated from within the planet, although Venus is obviously different internally, because its weaker magnetic field is generated in its upper atmosphere, also called the ionosphere, which interacts with the solar wind coming from the sun.[1]

Meteorite impact craters on Venus

Meteorite Craters on Venus
Credit: NASA public domain image.

NASA image of the surface of Venus created from radar data.

Is it possible for there to be life on Venus?

Life on Venus?
Credit: Image created by me using a NASA public domain photo for the background.

Certainly life such as what exists on Earth couldn’t possibly live on Venus. The surface of the planet is well over 800 degrees Fahrenheit (450 C), and even hotter than Mercury. With temperatures in between the hottest setting on your oven and molten lava, it is thought that the only possibility for Venusian lifeforms would be in the atmosphere’s lower and middle cloud layers.[1]

An interesting fact few people know about Venus is that although its massive amounts of atmospheric carbon dioxide create a greenhouse effect and are partly responsible for how hot the surface of Venus is, this isn't the only factor. Venus also somehow has a large amount of internal heat, and this is known because solar energy coming into the planet has been measured at a substantially lesser amount than what is being emitted back out into space.[7]

Along with the difference from Earth with how its magnetic field is generated, this is further evidence that the interior of Venus is far different from that of Earth, and much of the specifics remain unknown.

Probes sent to Venus, and the possibility of sending humans

Venus Probe
Credit: Artwork by NASA and in the public domain.

Artwork of a theoretical rover that could make its way across the surface of Venus, by NASA.

The surface of Venus is dimly lit, since most sunlight is reflected by the atmosphere back into space. There’s also extremely high atmospheric pressure (92 times that of Earth), wind that constantly moves dust and rocks across the surface, and ferocious lightning storms.[1]

A Soviet probe in 1966 became the first man-made object to ever land on another planet when it landed on the surface of Venus. Since the atmosphere was far thicker than what scientists had anticipated, the batteries ran out as it descended, and after 90 minutes of sending data the probe went kaput.[1]

Many other probes have landed on the planet. The first color photos were taken by a Soviet probe that landed in 1982. In 1989 an American probe mapped the surface using radar.[1]

The latest probe, sent by Japan in 2010, failed to enter the atmosphere as it was supposed to. Two flybys are planned for 2019 and 2020, when two probes headed for Mercury will use the gravity of Venus to aid in propelling them to the planet closest to the sun.[1]

Although proposals have been made for manned fly-bys, prospects for actually landing humans on the planet do not currently exist.[1]

The four rocky inner planets

Mercury, Venus, Earth, Mars

The Four Rocky Inner Planets
Credit: Public domain image by NASA.

True coloration and relative sizes of the four planets closest to our sun.

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Comments

Jan 21, 2015 8:57pm
RoseWrites
Wow, so a huge object struck Venus, causing it to spin in the opposite direction and its moon was "sucked" into the planet. I'm guessing that the orbit of Venus was also affected? And did its moon leave an impact or did it disintegrate on entry?

Fascinating stuff, I wonder how many astronomers are in total agreement about what happened. And yikes, it certainly causes me to consider that the same could happen to our Earth.

Sharing, pinning, G+ and all that good stuff.
Jan 21, 2015 9:50pm
TanoCalvenoa
Funny that you ask about Venus' orbit - because it's the most circular of all of the eight planets in our solar system, nearly a perfect circle. Mercury is the most elliptical, and I have to wonder if Venus was once more elliptical and was "corrected" into a more circular orbit by the violent collisions long ago.

As far as agreement amongst astronomers - there are always multiple theories, although what I presented above is what's most commonly accepted at the time of publication, and I'd change the article if something significant was discovered.

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Bibliography

  1. "Venus." Wikipedia. 21/01/2015 <Web >
  2. "Earth." Wikipedia. 21/01/2015 <Web >
  3. "Mars." Wikipedia. 21/01/2015 <Web >
  4. "Moons of the Planets." Go Astronomy. 21/01/2015 <Web >
  5. "What direction do planets rotate?." Curious About Astronomy. 21/01/2015 <Web >
  6. "Solar System." Wikipedia. 21/01/2015 <Web >
  7. "An Alternate View of Venus." Firmament and Chaos. 25/01/2015 <Web >

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