Author: Fraser Cain

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Earth has the Moon, Mars has two moons, and even tiny Pluto has 3 satellites. So how many satellites does Venus have? Well, Venus has no natural satellites today. However, it’s possible that Venus did have natural satellites in the past.

Perhaps the biggest evidence that Venus once had a natural satellite is its current rotation. Seen from above, all the rest of the planets in the Solar System rotate counter-clockwise. That’s why eastern countries have an earlier sunrise than western countries. But the rotation of Venus is very slow and backwards. Seen from above, Venus rotates clockwise. In fact, a day on Venus lasts 243 Earth days, while a year on Venus lasts almost 225 days.

With this slow, backwards rotation, it’s possible that Venus experienced a catastrophic impact in its early history, just like the impact that created the Earth’s moon. While our Moon formed out at a stable point where it’s been slowly drifting away, it’s possible that a moon around Venus formed at an unstable distance and just crashed down into the planet.

It’s also possible that Venus captured an asteroid or two in the past, as astronomers believe happened with the Martian moons Phobos and Deimos. And this might also help us figure out what happened to satellites around Venus. Phobos is in an unstable orbit, and is expected to crash into Mars in the next 10 million years or so. So it’s possible that Venus had unstable moons orbiting it in the past, and they crashed into the surface. Venus is also much closer to the Sun than Earth, so the solar tides might just be too powerful to allow Mercury or Venus to have moons.

Unfortunately, the entire surface of Venus was resurfaced between 300-500 million years ago, and any evidence of crashing asteroids or moons has been covered up by volcanic flows. So perhaps we’ll never know if Venus ever had satellites.

Of course, Venus does have artificial satellites. At the time this article was written, ESA’s Venus Express was in orbit around Venus, capturing images and gathering data about our twin planet. And there could be more missions in the future.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

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

References:
NASA StarChild: The Planet Venus
NASA Solar System Exploration: Planet Venus

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It’s been said that Venus is Earth’s twin planet, in terms of size and composition. So when you ask how big is Venus, you know it’s going to be pretty close to Earth. Of course, Venus has incredibly high temperatures, crushing pressure and a poisonous atmosphere, so it’s not exactly a twin of Earth.

Let’s start with the size of Venus. The diameter of Venus is 12,100 km. That’s about 95% of the diameter of Earth. If you put Earth and Venus side by side, it would be pretty hard to see which one was larger.

The volume of Venus is 9.38 x 10¹¹ km³, written out, that’s 938,000,000,000 cubic kilometers. Of course, since Venus isn’t as big as Earth, it actually has a smaller volume. Venus has only 86% the volume of Earth. In other words, you could fit 1.16 Venuses inside Earth.

The surface area of Venus is 4.6 x 10⁸ km². That works out to be 460,000,000 square kilometers. Again, that’s a little smaller than Earth. The surface area of Venus is only 90% the surface area of Earth.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

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

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In many ways Venus is Earth’s twin planet. It’s only a little smaller, and made up of the same composition as Earth. But when it comes to climate, Venus couldn’t really be more different. Venus is a hellish world – the hottest planet in the Solar System, with an average temperature of more than 400°C, and a surface pressure almost 100 times what we experience here on Earth. On top of that, there are clouds of sulfuric acid and other corrosive chemicals. Visiting Venus would be the worst vacation ever.

Before the 1960s, scientists thought that the climate of Venus might be similar to Earth. It has clouds, and here Earth, clouds mean rain, water, oceans and even life. But microwave observations of Venus showed that its surface must be incredibly hot, too hot for liquid water to exist. And spacecraft visiting the planet in the 1960s and 70s confirmed that the clouds of Venus are made up almost entirely of carbon dioxide; a potent greenhouse gas keeping the planet so hot.

But you could say that Venus has a climate. It has severe winds that blow at speeds greater than 100 m/s; although, the winds don’t reach down to the surface of the planet. It has sulfuric acid clouds which send down torrents of sulfuric acid rain.

The climate of Venus wasn’t always this harsh. In fact, Venus used to have an atmosphere similar to our own. But at some point in Venus’ past, its global magnetosphere shut down. Without this global force field, the Sun’s solar wind was able to reach the planet and tear away at its atmosphere, stripping away the lighter atoms. The lightest atom is hydrogen, of course, one of the constituents of water. Recent observations by ESA’s Venus Express showed that this process is still going on today. 2 x 10²⁴ atoms of hydrogen are being blasted off Venus into space every second.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

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

Reference:
NASA: The Solar System
NASA: Pioneer Mission to Venus

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When astronomers first pointed their rudimentary telescopes at Venus, they saw a world shrouded in clouds. Here on Earth, clouds mean water, so early astronomers imagined a tropical world with constant rainfall. The truth, of course is that the thick atmosphere on Venus is made almost entirely of carbon dioxide. In fact, the atmospheric pressure on the surface of Venus is 92 times more than what you would experience on Earth. If the clouds are carbon dioxide, is there water on Venus.

Well, there isn’t any water on the surface of Venus, in form of rivers, lakes or oceans. The average temperature on Venus is 461.85 °C. Since water boils at 100 °C, it couldn’t be on the surface. But could water be in the clouds and atmosphere of Venus?

Astronomers have detected that the atmosphere of Venus consists of 0.002% water vapor. Compare that to the Earth’s atmosphere, which contains 0.40% water vapor.

Scientists think that Venus had a similar formation to Earth, and it was certainly bombarded by the same comets that delivered vast quantities of water to our early planet. So why has Venus lost its water, while Earth kept its water? Recent observations by ESA’s Venus Express spacecraft found that Venus has a trail of hydrogen and oxygen atoms blasted away from the planet by the Sun’s solar winds. Every second, there are 2 x 10²⁴ hydrogen atoms streaming away from Venus. The Earth’s magnetosphere protects our atmosphere from the Sun, channeling the solar wind around the planet, and keeping it from reaching our atmosphere.

The Earth’s magnetosphere is generated by the convection of material deep inside the Earth. This happens because the large temperature difference between the outer core and the inner core. At some point, plate tectonics on Venus ceased, and the planet stopped releasing as much heat from the interior. Without a high temperature gradient, its inner convection stopped, taking away its planet-wide magnetosphere.

It’s estimated that Earth’s atmosphere and surface has 100,000 times as much water as Venus. And if we didn’t have our protective magnetosphere, we’d be losing our water too.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

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

Reference:
NASA Ask an Astrophysicist: Water on Venus

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Although humans have never made the voyage, spacecraft from Earth have visited Venus. So, how long does it take to get to Venus from Earth?

The first spacecraft ever launched towards Venus was the Soviet Venera 1 spacecraft. It was launched on February 12, 1961 on course to Venus. Unfortunately, scientists lost contact with the spacecraft on February 17th. Mission controllers didn’t get a chance to put in a course correction that would have directed it closer to Venus, so it’s thought to have passed within 100,000 km of the planet on May 19th. That’s a total time of 97 days; just over 3 months.

The first successful Venus flyby was NASA’s Mariner 2. This spacecraft was launched on August 8th, 1962 and made a successful flyby on December 14, 1962. So that calculates to 110 days from launch to arrival at Venus.

The most recent spacecraft to fly to Venus was ESA’s Venus Express. It was launched on November 9th, 2005, and took 153 days to make the journey to Venus.

Why is there such a big difference in travel times to Venus? It all comes down to the launch speed and trajectory. Both Earth and Venus are traveling on orbits around the Sun. You don’t just point your spacecraft directly at Venus and fire your rockets. You have to travel on a transfer orbit that moves you between Earth’s orbit and Venus’ orbit, catching up with Venus, ideally going into orbit. To make the trip with a smaller, less expensive rocket, you have to make a longer trip, taking more time.

Humans have never made the trip to Venus, but maybe someday they will; although, the planet would be extremely unpleasant to try and land on. Maybe just a flyby would be nice.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

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

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Want to lose some weight? Travel to Venus and you’ll feel lighter right away. Well, the high temperatures, intense pressures, and corrosive chemicals will make the experience unpleasant (and kill you instantly), but you’ll definitely be lighter on the scales. So what would your weight be on Venus?

The force of gravity on the surface of Venus is 90% the force of gravity you experience on Earth. In other words, if your bathroom scale reads 100 kg, it would only read 90 kg on Venus. For you imperial folks, if you weighed 150 pounds on Earth, you would weigh 135 pounds on Venus.

If Earth and Venus are considered twin planets, why wouldn’t you weigh the same? Well, Venus and Earth are very similar, but they’re not actually twin planets. Venus is only 95% the size of Earth, and 81% of its mass. With the smaller size and mass, the force of gravity pulling you on the surface is lower.

To get your weight on Venus, just multiply your current weight by 0.9. That’s why 100 pounds becomes 90 pounds. You can also do the reverse calculation and figure out how high you could jump, or what you could carry on Venus by dividing a number by 0.9. For example, the world record high jump is currently 2.45 meters. If that was done on Venus, it would be 2.72 meters (2.45 / 0.9).

Just one last thing. It’s important to note that kilograms are a measure of mass; how much stuff an object has. Your mass doesn’t change when you travel from planet to planet, or anywhere in the Universe. It would be more accurate to measure your weight in newtons, but bathroom scales don’t have that option. That’s why we say that your weight in kilograms changes from planet to planet.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

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

From our perspective here on Earth, Venus is completely covered in clouds. So what’s inside Venus? For most of history, scientists had no idea what’s inside of Venus. The earliest telescopes showed hazy cloud tops, and even the largest telescopes didn’t improve the view. Some astronomers thought they might have caught a glimpse of the surface through the clouds, or maybe the peak of a tall mountain poking up through the clouds. But we now know those were just observation errors.

It wasn’t until the first spacecraft from Earth arrived at Venus, and started gathering scientific data about the inside of Venus. NASA’s Mariner 2 helped scientists calculate that the density of Venus is very similar to the density of Earth. Although there were no direct observations of Venus’ interior, scientists assume that it must be similar to Earth. The inside of Venus is thought to contain a solid/liquid core of metal 3,000 km across. This is surrounded by a mantle of rock 3,000 km thick. And then there’s a thin crust of rock about 50 km thick.

When NASA’s Magellan spacecraft was launched to Venus in 1989, it was carrying a suite of powerful radar mapping instruments. These tools could pierce through the thick clouds surrounding Venus and reveal the surface of the planet in great detail. Magellan found that the surface of Venus is actually quite young, and was probably resurfaced 300-500 million years ago, based on the number of impact craters found on its surface.

Magellan also found evidence of a large number of volcanoes; they number in the thousands and maybe even in the millions. The shield volcanoes found across the surface of Venus indicate that the inside of Venus is still active, with magma pushing to the surface around the planet.

It’s believed that the event that resurfaced Venus 300-500 million years ago might have also shut down plate tectonics on Venus. Without the movement of plates to release trapped heat, the inside of Venus remained much hotter than it would be. It’s thought that this increase in heat also shut down the convection of metal around the core of Venus. It’s this convection in the Earth’s core that’s thought to run our planet’s magnetic field.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

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

References:
NASA Solar System Exploration: Terrestrial Planets
Venus Interior

Venus is a tricky place to study because it’s shrouded in a thick atmosphere that hides its surface. And if you can’t even see its surface, imagine how difficult it must be to study the interior of Venus. But scientists have been making steady progress towards understanding the interior of the planet, and learn about the core of Venus.

Here on Earth, scientists study the core of the planet by measuring how seismic waves move through the planet after earthquakes. As they pass through the different layers of the Earth’s interior; the core, the mantle, and the crust, the waves reflect or bend depending on the change of density that they’re passing through. Well, the surface of Venus is hot enough to melt lead, and spacecraft are destroyed within a few hours of reaching the surface of Venus, so no readings have been gathered about Venus’ core directly.

Instead, scientists assume that the core of Venus exists based on calculations of its density. The density of Venus is only a little less than the density of Earth. This means that Venus probably has a core of metal about 3,000 km across, surrounded by a 3,000 km thick mantle and a 50 km thick crust.

Scientists aren’t sure if the core of Venus is solid or liquid, but they have a few hints. That’s because Venus doesn’t have a planet wide magnetic field like the Earth. It’s believed that the Earth’s magnetic field is generated by the convection of liquid in the Earth’s core. Since Venus doesn’t have a planetary magnetic field, it’s possible that Venus’ core is made of solid metal, or maybe there isn’t enough of a temperature gradient between the inner and outer core to made this convection happen.

It’s believed that a global resurfacing event that occurred about 300-500 million years ago might have something to do with this. The entire surface of Venus was resurfaced, shutting down plate tectonics. This might have led to a reduced heat flux through the crust, trapping the heat inside the planet. Without the big heat difference, there’s little heat convection, and so no magnetic field coming from the core of Venus.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

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

References:
NASA Solar System Exploration: Terrestrial Planets
Venus Interior