Computer generated 3-dimensional perspective view of the “crater farm” on Venus (Magellan press release P-39146).
Up until the 1960s, the planet Venus conjured up a very different image in people’s minds compared to today. The brightest object in the night sky after the moon, Venus has been known since ancient times as the morning or evening star. A glance through a telescope reveals a white globe covered in an impenetrable layer of clouds.
The Soviets were the first to launch a robotic space probe to Venus in 1961, the Venera 1. While the first mission failed, both the Soviet Union and the United States remained determined to find out what lay beneath the permanent and all-encompassing thick white cloud cover of the planet. Enthusiasts speculated that the planet, long described as Earth’s twin, would be a hot jungle world teaming with exotic life. Alas, in 1962, the readings from the U.S.-launched Mariner 2 space probe found something quite different. Subsequent missions also confirmed that Venus was, in fact, one of the most inhospitable places in the Solar System. The luxuriant jungle world hypothesis was utterly quashed – instead, Venus was revealed to be the veritable biblical hell.
Welcome to the Infernal World of Venus
Image Credit: NASA/Ricardo Nunes
Venus has an average surface temperature of 460°C, hotter than the surface of Mercury in spite of being considerably further away than the sun. This enormous temperature, hot enough to melt lead, is believed to be caused by a runaway greenhouse effect (though opinions vary on this point, and rightly so). Many scientists believe that Venus absorbs (or reflects…depending on whom you ask) much of the sun’s heat and it gets trapped beneath the permanent wall of cloud. The leading theory currently is that the clouds are so thick, that they reflect 90% of the sunlight that hits the planet. This makes Venus a fairly dark and gloomy world despite that fact that it is actually closer to the Sun than Earth.
This burning dark world may already sound inhospitable enough, but that is nowhere near where it ends. Venus also has a crushing atmosphere with air pressures 92 times higher than those experienced on Earth at sea level. This is roughly equivalent to the pressure experiences over 1/2 mile beneath the surface of the ocean. All of the landing modules sent to Venus were ultimately crushed under this immense pressure. And still, it gets worse.
The Venusian weather is truly horrendous. The clouds that completely cover the surface spin more than twice faster than the strongest hurricanes on Earth. Above a dense carbon dioxide layer of the atmosphere are clouds filled with sulphuric acid. In the upper atmosphere, sulphuric acid rains from the skies, although this evaporates long before it meets the surface. Thunderstorms are constant and far more formidable than those experienced on Earth. Bolts of lightning rip through the skies adding to the nightmare.
To add to the hellish climate and atmosphere, Venus is also dominated by volcanoes. Much of the surface is covered by a smooth layer of volcanic basalt and planes of lava. Although there are at least 1600 large volcanoes on the planet, most of them are believed to be extinct. Nonetheless, the amount of sulphur constantly hurled into the atmosphere suggests that eruptions continue to occur in some areas.
Venus also has other properties making it distinctly different from Earth. The most notable is that the length of the Venusian day is 243 Earth days, making the day even longer than the year which is 224.65 Earth days. Even more bizarrely, Venus rotates in retrograde (backwards) motion. Venus has a negligible axial tilt whereas Earth has a tilt of 23°. This means that the planet has no seasons.
Venus almost completely lacks a magnetic field, something that is critical to life on Earth. The magnetosphere on Earth provides protection against cosmic radiation and without it, life on Earth would completely cease to exist. Venus also has no natural satellite (moon), so there are no tidal forces on the planet (except for those from the sun).
Venus was originally thought to be Earth’s sister planet until the true nature of its surface came to light. Nonetheless, Earth and Venus do share a few things in common. Venus has a very similar size and density to Earth. This means that the gravity is very similar. The planet’s composition is also quite similar.
Was Venus Once Like Earth?
Global radar view of the surface from Magellan radar imaging between 1990–1994
There is plenty of evidence to suggest that, billions of years ago, Venus was a more hospitable world than it is today. The Venus Express probe, launched in 2005, made some discoveries that support this evidence. Long ago, Venus’s atmosphere and surface contained hydrogen and oxygen – the two elements that make up water. As Venus lost its magnetosphere, any oceans would have evaporated over millions of years, being sucked out into space. When the planet was young, it could have experienced a brief habitable stage in which very basic forms of life may have formed. On the other hand, the entire surface may have also been extremely volcanically active and covered in molten lava flows rather like Earth in its earliest days before life came into being. However, even if life ever did exist on Venus, all traces of it are likely to have been long lost beneath a completely impenetrable surface of volcanic plains.
Future Human Exploration and Colonization of Venus
Since the discovery of the Venusian surface being so inhospitable, the world’s space agencies have turned their attention to the much more agreeable and promising conditions on Mars. It seems unlikely that any additional probes will be landed on Venus in the near future, although there has been a NASA proposal called the Venus In-Situ Explorer.
Colonization of Venus remains something belonging to the realms of science fiction but, it is not actually quite as outlandish as it may sound. In spite of the horrific surface conditions, Venus is also home to the most habitable place in the Solar System outside of Earth.
At an altitude of about 31 miles above the surface, the Venusian environment is by far the most similar to Earth in the Solar System. Air pressures here are about the same as they are on Earth at sea level and temperatures range from 0° to 50°C. This means that people would not even need to wear pressure suits in such an environment, although they would need to have air for breathing and some degree of protection from the sulphuric acid rain found in the upper atmosphere.
Colonizing this environment is almost certainly possible. Colonies would have to be located in aerostats floating about 50 kilometers above the surface (roughly 31 miles). These aerostats would not be tethered to the surface, but rather, would rotate at the same speed of the clouds, effectively making the Venusian day about four Earth days long. The aerostats would use a breathable mix of oxygen and nitrogen for lift, since these gasses provide far more lift than helium does on Earth thanks to Venus’s heavy, mostly carbon dioxide atmosphere.
Whether humanity will one day colonize Venus remains to be seen but, as our own world becomes progressively overcrowded and increasingly low on resources, such possibilities will eventually need to be taken seriously. I personally would rather take my chances with Mars or even the moon but I’m still a huge fan of Venus nonetheless.