Category: Guide to Space

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The bond albedo of Venus is 0.75.

Albedo is a measurement of the reflectivity of an object. A theoretically perfect reflecting object would have an albedo of 1, and reflect 100% of the electromagnetic radiation that falls upon it. While an object that was perfectly black and doesn’t reflect any light would have an albedo of 0. In real life, objects in the Solar System have albedo values between 0 and 1. And in the case of Venus, the albedo is 0.75.

Just for comparison, the bond albedo of the Moon is only 0.12. That’s actually pretty dark. The brightest albedo in the Solar System is Saturn’s moon Enceladus, with an albedo of 0.99. It reflects almost all of the light that falls onto it.

One of the reasons that Venus is so bright in the sky is because of its high albedo. This albedo comes from the permanent cloud layer that surround the planet. These clouds are made up of sulfuric acid that reflect much of the radiation that falls upon them.

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 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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Seen from Earth, Venus is a featureless ball; even the most powerful Earth-based telescope shows only clouds and more clouds. But those clouds are moving fast. The winds on Venus are powerful, circulating around the planet in just a matter of days. But because of Venus’ high temperatures and intense atmospheric pressure, they don’t behave like the winds on other planets.

The atmosphere of Venus extends up from the surface of the planet, up to an altitude of about 250 km. Down at the surface, the air pressure is 93 times higher than what we experience here on Earth. But once you rise up in altitude, the pressure drops to Earth surface pressure and then even lower.

At the very top of the cloud layers on Venus, wind speeds reach 355 km/hour (or 100 meters/second). This is the same the jet stream here on Earth. As you descend through the cloud layers, though, the wind speeds pick up. In the middle layer, the winds can reach speeds of more than 700 km/hour. That’s faster than the fastest tornado speed ever recorded on Earth.

But then as you descend further down through the clouds, the thickening atmosphere slows the winds down, so that they act more like currents in the ocean than winds in the atmosphere. Down at the surface, the winds only move at a few km/hour. That’s not much, but the thick atmosphere can still kick up dust and push around small rocks.

The winds on Venus travel in a westerly direction, the same backwards direction that Venus rotates. Seen from above, Venus rotates in a clockwise direction. This is backwards from the other 7 planets, which rotate counter-clockwise.

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 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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Scientists call Venus Earth’s twin planet and for good reason. Our two planets are similar in size, mass, density, gravity, and composition. Of course, they have some enormous differences as well; differences that would kill you instantly if you tried to step foot on Earth’s twin planet. Earth’s evil twin planet, maybe.

Let’s look at the similarities first. For starters, the size of Venus is very close to Earth. The diameter of Venus is 12,103.6 km. That’s only 95% of the Earth’s diameter of 12,756.2 km. If you put the two planets side by side, you’d have a hard time telling which one’s bigger.

The volume of Venus is 85.7% the volume of Earth, and it has 90% of the Earth’s surface area. The mass of Venus is 81.5% the mass of the Earth, and even the force of gravity is only 90% of what you experience here on Earth.

The composition of the two planets is similar too. Both have metal cores surrounded by a mantle of silica rock, and then a thin crust. There are some differences here, though. Earth’s core has convection which generates the planetary magnetic field, while Venus doesn’t have a similar magnetic field. Earth has plate tectonics, which help release heat from within the planet, while Venus doesn’t.

But there are bigger differences. And this is where it’s better to consider Venus as an evil twin planet. The temperature of Venus across the whole planet is 461.85 °C. That’s hot enough to boil lead! Spacecraft from Earth have only lasted a couple of hours at maximum because of the incredible temperatures. In fact, Venus is the hottest planet in the Solar System.

And if the temperature isn’t bad enough, the air pressure is even worse. The atmospheric pressure on the surface of Venus is 93 times higher than what you’d experience on Earth. In fact, you’d have to travel a kilometer beneath the surface of the ocean to experience that kind of pressure. While Earth’s atmosphere is made up of oxygen and nitrogen with trace amounts of carbon dioxide, Venus’ atmosphere is 96.5% carbon dioxide with the rest nitrogen. It has clouds of sulphuric acid that rain down to add to the planet’s lethality.

Earth has vast reserves of water, while Venus is almost completely dry. There are no reserves of water on the surface of Venus, and just a trace amount of water in its atmosphere. Because Venus doesn’t have a global magnetic field, it’s constantly pummeled by the Sun’s solar wind, which strips the lightest elements out of its atmosphere. Satellites have detected a constant stream of hydrogen atoms streaming away from Venus, lost from the planet forever.

And just one last difference, Earth has the Moon, but Venus has no moons. It might have had a moon in the past, but it’s believed to have crashed into the planet a long time ago.

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 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 Solar System Exploration: Venus
NASA Solar System Exploration: Earth

Venus might look like a virtual twin of the Earth in terms of size, but its temperature and atmosphere make it very different from the Earth. The temperatures can reach almost 500°C, and the atmospheric pressure is almost 100 times what you would experience on the surface of Earth. With such a terrible environment, you might be surprised to know that spacecraft have landed on Venus (although, they sure didn’t last long).

The first spacecraft to enter the atmosphere of Venus was the Soviet Venera 3 probe, which crash landed on March 1, 1966. It was destroyed in the upper atmosphere, so it wasn’t able to return any useful information back to Earth.

The next spacecraft to attempt a landing on Venus was the Soviet Venera 4 spacecraft, which entered the atmosphere on October 18, 1967. Venera 4 was able to deploy several science experiments and was operating them as it passed down through Venus’ atmosphere. But mission planners didn’t realize that the atmosphere of Venus was so thick, and so it ran out of battery power about 25 km above the surface of Venus. But this failure helped missions planners better understand conditions on Venus.

The Venera 7 spacecraft was built to handle 180 times Earth atmospheric pressure, and used a special parachute to drop it down quickly through the atmosphere. It’s believed that the parachute partially failed, and so it impacted the surface of Venus hard. It was only able to return temperature data back to Earth for about 20 minutes.

Venera 8 survived for 50 minutes on the surface of Venus, sending back data.

But the first photographs taken from the surface of Venus were sent back by the Venera 9 and 10 spacecraft. Venera 9 landed on the surface of Venus on October 22, 1975 and operated on the surface of Venus for 53 minutes. It sent back the first images ever captured from the surface of Venus. Venera 10 landed on October 25th, and captured images of pancake-shaped lava rocks. Venera 10 lasted for 65 minutes, and was able to see farther into the distance than Venera 9.

But the most successful Venus landings were the Soviet Venera 13 and 14, which touched down on March 1st and March 5th, 1982. They both survived for over an hour, and returned the first color images ever captured from the surface of Venus.

All of the spacecraft that ever landed on Venus are probably still there today.

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.

Reference:
NASA Solar System Exploration: Missions to Venus
NASA: Mission to Venus Timeline
NASA Planetary Science: Mission to Venus

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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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For seventy-six years, ever since Pluto was discovered in 1930, we had 9 planets in our Solar System. This all changed in 2006 when Pluto was demoted to the category of dwarf planets.

Mercury was only the second smallest planet back when there were 9. Mercury is closer to Earth than a number of other planets, but we cannot get a very good look at it because of its proximity to the Sun. Astronomers cannot use the Hubble Space Telescope to look at the planet because the Sun’s light would permanently damage the piece of equipment.

Venus is the brightest of all 9 planets. The only objects brighter in the Solar System are the Sun and the Moon. Venus is so bright that it can actually cast shadows. If the Moon is not out one night, you may be able to find some shadows thrown by the planet.

Earth is the densest of all planets in our Solar System. Our planet is composed mostly of iron, silicon, magnesium, and oxygen. Almost one-third of the planet (32.1%) is iron. There is nearly as much oxygen in the planet – 30.1%. There are lesser amounts of silicon (15.1%) and magnesium (13.9%). The materials are not spread equally throughout the planet. For example, most of the iron is in the core of the planet.

Ever since astronomers spotted what looked like canals on Mars, they have been searching for water and signs of life. While life has not been discovered yet, scientists have found deposits of water underneath the surface of the planet.

Not only is Jupiter the largest and most massive planet in our Solar System, but it is also the fastest spinning planet. Jupiter completes a full rotation in about 10 hours. The planet has actually flattened slightly at both ends due to the speed at which it spins.

Saturn does not have the most moons of any planet in our Solar System – that distinction goes to Jupiter with 63 moons – but Saturn comes in a close second with 60 moons. When Galileo first saw Saturn with a telescope, he thought that the planet’s rings were moons. Astronomers were not able to determine what the rings were until they developed better telescopes.

Uranus is the only planet to rotate on its side. This planet has the greatest axial tilt of any planet in our Solar System – 98°. As a result of this extreme tilt, the north pole is in darkness for 42 years then it gets 42 years of light before repeating the cycle.

Neptune is quite a bit larger than Earth, but its gravity is very similar. If you could stand on Neptune – you cannot because it does not actually have a surface – then you would only experience approximately 17% more gravity than you would standing on Earth.

Pluto, which was discovered in 1930, was the ninth planet. Pluto was by far the smallest planet. In fact, Pluto is even smaller than the Earth’s moon. This tiny planet was also the coldest one. Although its temperatures can drop to -240°C, the average temperatures on Pluto are -219°C.

Universe Today has articles on all 9 planets of the solar system including list of the planets and planets in the Solar System.

If you’d like more info on the nine planets, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

Astronomy Cast has episodes on all the 9 planets of the Solar System including Mercury.