Venus

Overview

When Venus was first studied in modern times, scientists saw a beautiful world that was almost the size of Earth, and it had a thick cover of clouds. The picture to the right shows what Venus looks like when seen in ultra-violet light (UV shows more contrast in the clouds). For years, Venus was called Earth's Sister Planet, and much popular science and science fiction literature was devoted to what might lie below the huge clouds. All that changed once scientists were able to measure what those lovely clouds were made of: Poisonous gases.

Venus' atmosphere is so thick that a barometric reading (a measure of pressure) would be between 90 to 100 times higher than Earth's, which is the equivalent on Earth of being underneath 1 km of water. Its atmosphere is 97% carbon dioxide. This green-house gas retains almost all of the heat Venus' surface gets from the sun, and its surface temperature of 480 °C (896 °F) is the same on both sides of the planet due to the insulating nature of the clouds. This temperature is hot enough to melt lead. The clouds are rich in sulfuric acid, so any type of precipitation would "burn" with acidity.

Scientists have mapped more of Venus' surface than that of the Earth. While we cannot see beneath the clouds in visible light, we can bounce radar off the planet's surface. The radar that is reflected can then be used construct a map of the surface. This is the same principle that bats use to see in the dark, dolphins use to communicate, and we use to map Earth's ocean floor. There is only a small section of Venus that has not been mapped. The image to the left is a false-color image of what Venus would look like if stripped of its clouds. The darker colors indicate lower features, and the brighter colors indicate higher features.

From the data currently available, Venus is a world composed of mountains, flatlands, and valleys -- much like the rugged terrain found on Earth. The surface has relatively few craters, which suggests that there was either recent or current volcanic activity that has erased older craters.

Atmosphere

As can be seen in the planetary data table below, Venus' atmosphere is nearly 100 times as massive as Earth's, and its thick cloud layers block the surface from view. It exerts a pressure of approximately 92 bars at the surface. Its composition is nearly all CO₂.

Venus is the case of a runaway greenhouse effect. The temperature and pressure of the atmosphere decrease with height, so water vapor rises in the atmosphere and encounters conditions that cause it to condense back into liquid water and fall back to the surface - a region called the "cold trap." On Earth, this is at a height of 9-15 km (5-9 miles) above the surface, but on Venus it lies at an altitude around 50 km (31 miles) due to the planet's closer proximity to the sun.

On Earth, the ozone layer is several kilometers above this, and the ozone prevents ultraviolet light from destroying water in our atmosphere. On Venus, there is no ozone layer, and the atmosphere doesn't become opaque to ultraviolet light until a depth is reached below the cold trap. This allows ultraviolet light to destroy water between this height and the cold trap's.

So, as water rises in Venus' atmosphere and reaches this region, UV light dissociates it into two hydrogen atoms and one oxygen atom. The hydrogen is much lighter than the water molecule was, and so it easily escapes Venus' atmosphere. The water will usually quickly recombine with a carbon or carbon monoxide molecule to form carbon monoxide or carbon dioxide. This is probably one reason why there is so much carbon dioxide in Venus' atmosphere today.

Heavy water, however, which is composed of one oxygen, one hydrogen, and one deuterium (a proton and one neutron), cannot reach the requisite height as easily. If it does, it can still be dissociated just like normal water, but this happens at a much slower rate. Thus, a measurement of how much deuterium compared with how much hydrogen today shows that Venus has much more deuterium in its atmosphere for each hydrogen atom than Earth does. This is the strongest evidence that Venus has lost a massive amount of water in its history.

This process is a runaway one in that once less water is available to wash CO₂ from the atmosphere, the CO₂ level rises. This results in a stronger greenhouse effect, so the temperature rises. The higher temperature moves the cold trap higher, and the cycle continues at an accelerated rate because there is a larger region where water can become dissociated.

Geology

[To be inserted.]

Mythology and Naming Schemes

Venus is named after the ancient Roman goddess of love. When scientists first spotted it, they saw beautiful swirls of clouds, and thought that they hid a world of beauty that was Earth-like, and would contain life. They couldn't have been more wrong.

Since Venus is the only planet named for a female, every surface feature of Venus is named for a female, too; however, there is one exception: The largest mountain range on Venus is called Maxwell Montes, which is commonly referred to as "The Only Man on Venus."

Other features are given names as:

• Astra (radial patterns), fluctus (flow terrain), labyrinthi (complex intersecting valleys), montes (mountains), and tholi (small domical mountain or hill) are named after goddesses and other miscellaneous females.
• Chasmata (deep, elongated, steep-sided depressions) are named after goddesses of the hunt and moon.
• Colles (small hills or knobs) are named after sea goddesses.
• Coronae (ovoid-shaped features) are named after fertility and Earth goddesses.
• Craters that are larger than 20 km are named after dead women who have made fundamental contributions to their field, while craters that are smaller than 20 km are given common female first names.
• Dorsa (ridges) are named for sky goddesses.
• Farra (pancake-like structures or a row of them) are named after water goddesses.
• Fossae (long, narrow, shallow depressions) and Lineaeare (dark or bright elongated marking) named for goddesses of war.
• Paterae (irregular crater or a complex one with scalloped edges) are named for famous women.
• Planitiae (low plains) are named for mythological heroines.
• Plana (plateau or high plain) are named for goddesses of prosperity.
• Regiones (large area marked by reflectivity or color distinctions from surrounding areas, or a large geographic area) are for giantesses and titanesses, though two are named after the first two letters of the Greek alphabet.
• Rupes (scarps) are named for goddesses of hearth and home.
• Tesserae (tile-like, polygonal terrain) are named for goddesses of fate and fortune.
• Terrae (extensive land masses) are named for goddesses of love.
• Undae (dunes) are named for desert goddesses.
• Valles (valleys) longer than 400 km are named after various words for the planet Venus in other languages, while those shorter than 400 km are named after river goddesses.

Data for the Planets