Universe Today

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Venus is one of the planets visible with the unaided eye. Because it has always been easy to see, it’s impossible to say who discovered Venus. In fact, after the Moon and the Sun, Venus is the brightest object in the sky – it’s likely ancient people thousands of years ago knew about it.

You can’t really talk about the discovery of Venus, but historians do know when observations of Venus were first written down. In fact, one of the oldest surviving astronomical documents is a Babylonian text that talks about Venus in 1600 BC. It contains a 21-year record of Venus’ appearances. Venus played a part in the mythology of many ancient peoples, including the Mayans and the Greeks.

The first person to point a telescope at Venus was Galileo Galilei in 1610. Even with his crude telescope, Galileo realized that Venus goes through phases like the Moon. These observations helped support the Copernican view that the planets orbited the Sun, and not the Earth as previously believed.

Astronomers predicted that Venus would transit across the surface of the Sun. The first time this was observed was on December 4, 1639, and later transits helped astronomers discover that Venus has an atmosphere, and helped calculate the distance from the Earth to the Sun with great accuracy. The last transit of Venus happened in 2004, and the next one will happen in 2012.

Although the surface of Venus is obscured by thick clouds, radar signals were bounced of the surface of the planet in 1961. This allowed astronomers to calculate its radius accurately, and measure its speed of rotation. They also discovered that its axis of rotation is almost zero.

The first spacecraft to actually visit Venus was NASA’s Mariner 2, which flew past Venus in 1962. More recently, NASA’s Magellan spacecraft visited Venus and extensively mapped it surface with radar. ESA’s Venus Express arrived at Venus in May, 2006.

You might be surprised to know that Russian spacecraft have actually landed on the surface of Venus. Although there were several failed attempts, the first spacecraft to actually land on the surface of Venus and survive was Venera 7; although, it was only able to transmit for about 35 minutes.

So, it’s hard to say who actually discovered Venus. The first caveman who stepped outside in the early evening would have noticed bright Venus. But since the discovery of the telescope, and the beginning of the space age, scientists have really been able to discover Venus.

Here are articles about two planets in the Solar System that were actually discovered in recent times. Here’s an article about the discovery of Uranus, and here’s an article about the discovery of Neptune.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

References:
NASA: Transit of Venus
NASA Solar System Exploration: Venus

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The volume of Venus is 9.38 x 10¹¹ km³.

That sounds like a big number, and it is. Here’s the long version: 938,000,000,000 cubic kilometers. Just for comparison, the volume of Venus is 86% the volume of the Earth. That’s why many scientists consider Venus to be the twin planet to Earth. Of course, when you consider that the temperature on the surface of Venus is hot enough to melt lead, and atmospheric pressure is 92 times what you would experience on Earth, and Venus doesn’t exactly seem like Earth’s twin.

Of course, the volume of Venus is just a tiny fraction of the volume of the Sun. You could fit 1.5 million planets the size of Venus inside the Sun and still have room to spare.

It’s hard to study the interior of Venus, but scientists think that the volume of Venus is very similar to the volume of the Earth. The planet has a core of liquid metal surrounded by a mantle of molten rock. This is covered by a crust of solid rock.

Want to know about other objects in the Solar System? Here’s the volume of the Moon, and the size of the Sun.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

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The size of a planet is measured in many ways: mass, volume, equatorial diameter, and surface area are the most common. In this article we are going to explore each of these ways to express the size of Venus and a few interesting facts about our close neighbor.

Venus has a diameter that is about 95% of Earth’s. It is 12,100 km across. The Venusian surface area is around 90% of our own at 4.6×10⁸ km². The planet has a volume of 9.38×10¹¹ km³. That puts it a little over 85% of Earth’s volume. One final way to measure the size of Venus is to consider its mass. It has a mass of 4.868 x 10²⁴ kg., just over 81% of Earth’s. These physical characteristics have led many scientists to call Venus the sister planet of Earth.

Size characteristics are the only things that Earth and Venus have in common. At 462°C, Venus has an average temperature that is 410°C higher than the hottest deserts on Earth. The temperature on the Venusian surface can melt lead. You have to be 50 km from the surface to find temperatures that are anything like here on Earth.

Temperature is not the only extreme on Venus. The atmosphere would prevent any life as we know from surviving. To start with, the atmospheric pressure is 92 times that of Earth. It is choked with volcanic ash, sulfuric acid clouds, and is made of 95% carbon dioxide. There are constant hurricane force winds churning the atmosphere. Sustained winds in excess of 360 kph are always present. The conditions on the planet are so extreme that probes can only last a few hours.

The surface shows over 1000 volcanoes or volcanic remnants that are over 20 km in diameter. There are no small impact crater, because the atmosphere is too thick to allow small objects to penetrate to the surface. Scientists believe that the entire surface of the planet was been replaced by volcanic activity 300 to 500 million years ago.

Venus has been visited by spacecraft several times. NASA sent Mariner 2 in 1962. It was the first spacecraft to send information from another planet. The Soviet space program landed Venera 7 in 1970. It was the first spacecraft to land on another planet. NASA’s Magellan mapped 98% of the surface in the early 1990s and the European Space Agency currently has the Venus Express in orbit studying the planet’s atmosphere. In all, we have gained a great deal of information about this inhospitable planet in the last 30 years.

Want to know the size of other planets in the Solar System. Here’s an article about the size of Jupiter, and here’s an article about the size of Saturn.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

References:
http://www.nasa.gov/audience/forstudents/5-8/features/F_The_Planet_Venus_5-8.html
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=OverviewLong
http://en.wikipedia.org/wiki/Venus

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The radius of Venus is 6,052 km. Double that and you get the diameter of Venus: 12,104 km.

Need some comparison? The equatorial radius of Earth is 6,378 km, so the radius of Venus is 95% the Earth’s radius. With such a similar size, you can see why Venus is considered Earth’s twin planet (evil twin, really, when you consider it’s hot enough at the surface to melt lead, with an atmosphere 92 times as thick as Earth).

With other planets in the Solar System, we talk about their equatorial and polar radii. That’s because most planets are rotating on their axis so quickly they’re a little flattened out, with a bulge around the equator. For example, here on Earth, points at the equator are actually 7 km further from the center of the Earth than the poles.

Venus, on the other hand rotates so slowly on its axis that it isn’t flattened out at all. While Earth takes 24 hours to complete one rotation, Venus takes 243 days to spin once on its axis (it also rotates backwards compared to the other planets in the Solar System, but that’s another story).

So the radius of Venus is 6,052 km, whether you calculate it from the center to the equator, or the center to the poles.

Want to know the radius of other planets? Here’s an article about the radius of Mercury, and here’s an article about the radius of the Moon.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

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The mass of Venus is 4.868×10²⁴ kg. That is about 82% of the mass of Earth. Alright, end of story and thank you for reading. Okay, we would never do that to you here at Universe Today. There are far too many interesting facts about Venus to leave you hanging like that.

Here are a few other physical characteristics of the second rock from the Sun:

Scientists believe that the high mass and density of Venus can be accounted for by its high concentration of rock and metals. They believe that the planet has a liquid metallic core that is surrounded by a molten rock mantle. Actual proof of this is nearly impossible since the reflective nature of the planet’s atmosphere makes many types of observation impossible.

Venus was once thought to be a dead planet. There is no life on the surface for many reasons, but recent study of the surface has revealed that there may be active volcanoes on the planet. That means that it is alive, geologically speaking. Previously, scientists had known that the planet had been resurfaced by volcanic activity 300 to 500 million years ago, but had thought that the activity died out during that same time frame.

There have been many missions sent to Venus. The Soviet space program started the race to Venus with the Venera program. It is hard to tell exactly how many Soviet missions to Venus were launched since the program would not announce a probe that failed, but more than a dozen were successful. NASA launched several mission of its own. Early missions from both programs failed because neither was prepared for the extreme pressure within the Venusian atmosphere. Even those that were able to transmit from the surface could only survive for less than one hour.

The Venus Express is currently in orbit around Venus. BepiColumbo is set to launch in 2014. It is hoped that the Akatsuki probe can reawakened to gather information when it arrives in the area in 2016 and the Venus In-Situ Explorer is in the planning stages. Scientists are determined to unravel the planet’s mysteries. Like you, they want to know more than the mass of Venus.

Here’s an article about the mass of Mercury, and here’s an article about the mass of the Earth.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

References:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=Facts
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=OverviewLonghttp://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=Educ

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Although it’s similar in size, Venus is very different from Earth. The temperature at the surface is hot enough to melt lead, with an atmosphere of almost pure carbon dioxide, 92 times thicker than Earth’s atmosphere. Even with this extreme environment, is it possible that there’s life on Venus?

Probably not.

Here on Earth, we find life wherever we find liquid water: kilometers deep underground, beneath glaciers, and even inside nuclear reactors. If there’s liquid water, there’s life. But there doesn’t seem to be any liquid water on Venus.

Scientists think that Venus did have liquid water billions of years ago, but a runaway greenhouse effect heated up the planet to the point that all the water evaporated, and was eventually lost to space. The atmosphere is now 96% carbon dioxide, with the rest nitrogen and a few other trace compounds.

But there’s another possibility. High up in the atmosphere of Venus, at an altitude of 50 km, the air pressure and temperature get to the point that they’re very similar to Earth. In fact, at this altitude, it’s the most Earthlike place in the whole Solar System. Some scientists think that there could be microbial life high up in the atmosphere of Venus.

Since the Sun’s solar wind is constantly blowing on Venus, and Earth is “downwind” from Venus, it’s possible that microbial life is being blown from Venus to Earth. Maybe life on Earth got its start on Venus.

You can read a longer article about the possibility of life on Venus here. And here’s a video that shows how the atmospheres of Venus and Mars leak into space.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

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When you look at the Moon and Mercury, their surfaces are pounded with impact craters. Mars has many craters, and even Earth has its share. But what about Venus, are there craters on Venus?

There are craters on Venus, but not many. The Solar System is relatively empty now, but less than a billion years after the formation of the Solar System, there were still many objects left over. These crashed into planets and moon, during a time scientists call the late period of heavy bombardment. Many of the craters on Mercury and the Moon were formed during that time.

Strangely, Venus shows no record of the heavy bombardment period. Either it didn’t get struck, which is unlikely, or some process resurfaced the planet, removing all traces of the impact craters. The resurfacing process stopped at some time in Venus’ more recent history. And so, all the craters that scientists do see on the surface of Venus are relatively young.

Craters on Venus are different from craters on other planets. The planet’s thick atmosphere stops the smaller objects from even reaching the surface of Venus; they just burn up in the atmosphere. There are about 1000 craters identified on the surface of Venus.

Crater Mead is the largest known crater on Venus, named after the American anthropologist, Margaret Mead. It measures 280 km in diameter, and contains several concentric rings.

We have written many articles about Venus on Universe Today. Here’s an article about the evolution of Venus’ surface, and here’s a “Where in the Universe” challenge featuring a crater on Venus.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.