Venus — The Lab


On Venus you can probably see the back of your head. It's the flattest planet in the inner Solar System, and for some unknown reason, it turns the opposite way to practically all the other planets. It is almost an identical twin to Earth in mass and size, and yet it is the hottest of all of the planets - it's even hotter than Mercury which is closer to the Sun. On Venus, a "day" is longer than a "year". And we know the surface of Venus better than the surface of our own planet, Earth

Venus is the brightest of all the "stars" in the sky. It's named after the goddess of love. It's always covered with thick cloud, so we can't see its surface. That could be why more spacecraft (about 20) have visited Venus than any other planet.

Even though Earth and Venus are almost the same size, Venus has much more atmosphere or gas. The pressure at ground level is nearly 100 times the pressure at sea level on Earth. The atmosphere is about 97% carbon dioxide and about 3% nitrogen. In fact there's roughly as much nitrogen on Earth (where it makes up 80% of our atmosphere) as there is on Venus.

The atmosphere is so thick, that according to some scientists, it would bend the light in a complete circle. So no matter where you looked, you would always see the back of your head - if the atmosphere were clear enough to see any distance at all.

On Earth, the clouds have just about finished by 15 km above sea level. On average, about 50% of the surface of the Earth is covered by cloud at any given time. But on Venus, the clouds cover 100% of the planet all of the time. The clouds begin at 50 km above the surface, and then continue for another 25 km above that. The clouds are made of droplets of sulphuric acid, which are about 50 times smaller than the thickness of a human hair. Venus takes 225 earth-days to make a complete loop around the Sun. We don't yet know why, but Venus rotates in an opposite direction to all the other planets in the Solar System (except Uranus). In fact, it rotates very slowly, and a Venus Day lasts 243 Earth Days. So on Venus a day is longer than a year.

Every 584 days, Venus and Earth come to their point of closest approach. And every time this happens, Venus shows Earth the same face. Is there some force that makes Venus align itself with the Earth rather than the Sun, or is this just a coincidence?

The temperature on the surface of Venus is about 480oC - hot enough to melt the zinc off your tin roof. But this enormous temperature is not just because Venus is closer to the Sun than we are. In fact, about two thirds of the energy of the Sun is absorbed by the clouds, and only one third of the heat energy reaches the ground. In fact less solar energy reaches the ground on Venus than on Earth. The reason that Venus is so hot is because of a massive runaway Greenhouse effect. Any heat that does get inside the clouds is trapped there.

Lightning seems to be as common on Venus as it is on Earth. Most of the lightning happens within the thick high cloud deck. Venus rotates very slowly. The clouds on Venus race around the planet some 60 times faster than the surface. They do a complete circle every 4 Earth days so the clouds pass through the planet's afternoon on roughly the same time scale as the clouds do on Earth. And just like on Earth, the thunderstorms and lightning on Venus seem to happen mostly in the afternoon and at dusk.

The most recent spacecraft to visit Venus was Magellan. The Magellan photographs show a very regular channel 4,000 kilometres long and 1 kilometre across. The Magellan photographs also show a mountain taller than Mount Everest.

Thanks to Magellan, Venus is mapped better than our planet Earth. 70% of the surface of our planet is covered by water, and we have very poor maps of the surface under the sea. But 95% of Venus has been mapped by Magellan. In fact Magellan has discovered so many new features (such as craters) on Venus, that the scientists have run out of names for them. But you can submit a person's name for a feature on Venus. By international agreement, features on Venus have to be named after famous and notable women. There are a few rules. The woman must have been notable and in some way worthy of the honour. She cannot have been a military or political figure from the 19th or 20th centuries. She cannot have been a person who was famous in any of the six major religions on our planet. She cannot have been a person who was famous only in one country. She must have been dead for at least three years.

Send your list of names to: Venus Names, Magellan Project Office, Mailstop 230-201, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA. Be sure to include her dates of birth and death, and a few reasons why she should receive this honour. A photostat from a book mentioning her is even better. Venus is a land of gigantic lava flows, thousands of craters, and strange features showing that very fierce volcanic activity has happened there. There are long rift valleys, huge craters and uplifted areas, and the crust of the planet is cracked and splintered.

But overall, Venus is incredibly flat. The average radius of Venus is 6,051.4 kilometres. About 70% of the planet is within 500 metres of this average radius. If you were to take all of the water that there is on Earth, and somehow magically pour it onto Venus, only two continents would appear above the surface. Between them these two lands cover about 10% of the surface. In the same way that the continents on our planet are an average of 3 kilometres above the average level of the ocean floor, these lands on Venus are 3 kilometres above the lands that would be below sea level.

In the northern hemisphere is a land called Ishtar (the Babylonian goddess of love). Ishtar is roughly the size of Australia. In the southern hemisphere is the other continent, Aphrodite (the Greek goddess of love), about the size of Africa or twice as big as Ishtar. There is a large diamond on Venus. This diamond helped to prove that Murphy's Law works on other planets besides Earth.

The Soviets used the diamond as a front glass to protect the lens of the camera on their spacecraft. Venera 13 and Venera 14 sent back colour photographs of the surface of Venus. On the way down through the atmosphere, the lens cap was left on the camera to protect the lens from the clouds of sulphuric acid. But once the spacecraft had landed, the lens cap was thrown off, exposing the diamond front glass. Diamond is the hardest substance known in the Universe to the human race, and the Soviets thought that it would not be affected by the terrible atmosphere.

Each spacecraft also had an experiment called the "Dynamic Penetrometer". The Penetrometer was a spring-loaded arm with a point on the end of it. The point would penetrate deep into soft ground, but not so deep into hard ground.

The photographs from Venera 13 show the penetrometer point embedded in the soil, and the lens cap off to one side. But the photographs from Venera 14 show that the point of the penetrometer landed exactly on the lens cap. This is proof that Murphy's Law is a universal law. The diamond is still waiting on the surface of Venus. If you want to get it, all you need is the space fare.

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Source: ABC Australia

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