The Romans christened her the goddess of beauty and love. Her gentle radiance has attracted the eye ever since man began to look at the sky. Until the middle of the last century, no one would have guessed that behind this ethereal, pale blue glow hides a planet from hell.
Covered with oceans and rainforests, the globe resembles the Amazon Jungle, and the temperature on its surface is not too different from Earth’s (despite the 400 million kilometers separating us) – back in the 1950s, this is how Venus was imagined. A decade later, it turned out that this idyllic picture is not true in the slightest.
The second planet from the Sun used to be called Earth’s twin sister and this impressive comparison has almost become a cliché. Because it must be admitted that the apparent similarities between the two celestial bodies can be deceiving. Although Venus does not have a moon, both planets are rocky and about four billion years ago most likely formed from the same gaseous mother cloud. In addition, Venus is only slightly smaller and slightly lighter than Earth and has a similar gravity to Earth. Add to that the fact that it is at a similar distance from the Sun (on the scale of the entire Solar System, of course), it is hardly surprising that for so long it appeared to be a friendly world and relatively not too far from ours. The presumptions of scientists from before the Venusian probe era were laid to rest when the first man-made spacecraft arrived in its vicinity.
The goddess of love reveals her face
The trail was blazed by Soviet Veners sent since 1961, although only their fourth mission was successful. But the real breakthrough was made by the Americans when NASA launched the Mariner 2 probe in 1962. The spacecraft did not penetrate the planet’s atmosphere (it approached at a distance of 34 000 km), but it provided a lot of very interesting data. First of all it revealed a surprising anomaly: Venus rotates around its axis in the opposite direction than the Sun. In addition, the probe has dispelled any illusions about the Venusian climate. The surface temperature is nearly 500°C, making Venus the hottest planet in the Solar System. Even Mercury, which orbits closest to our brightest star, is cooler.
In 1964, thanks to a radio telescope in Puerto Rico, another peculiarity was discovered: Venus rotates the slowest of all the known planets. A day on it lasts 243 Earth days and nights, and a round around the Sun takes it about 225 days. So as you can easily see, a day there lasts longer than a year.
The more probes reached their destination (the next Mariners and Veners, in the 70’s), the longer it took to get there. The more alien and dangerous the planet bearing the name of the goddess of love turned out to be. Instead of the expected tropical paradise, we discovered a sulphurous hell, shrouded in a reddish glow.
It’s really hard to find a more terrifying world. The pressure there is almost 100 times higher than the Earth’s pressure. It would easily crush a passenger car (such a fate met the first Veners landing on the planet’s surface, thanks to which we finally got to see the face of the planet so closely). The temperature, as we have already mentioned, reaches unimaginable proportions – enough to melt lead. Under its influence, the rocks omnipresent there. glow in the dark.
The sky is covered by a thick layer of clouds formed from droplets of sulfuric and hydrochloric acids. This dome completely obscures both the sun and the stars, so that everything is bathed in an eerie reddish light. Visibility is only a few hundred meters. Rains of sulfuric acid or lead sulfide are common. However, they do not reach the surface, settling only on the mountain tops.
Although the areas have been given nice sounding names derived from women’s names (e.g. Land of Aphrodite, Latin Aphrodite Terra), it is just a fire-drenched desert, full of basalt boulders and covered with coarse sand. Adding variety to the Dantean landscape are huge asteroid impact craters and dormant volcanoes reaching the height of Earth’s Himalayan peaks (the highest, Maat Mons, rises to 8000 meters).
As if all this was not enough, probes sent in the 21st century have discovered that in the atmosphere of this globe, at an altitude of over 60 kilometers above the surface, gigantic hurricanes are roaring, in comparison with which those of the Earth seem to be as gentle as a warm spring breeze.
Why did the “twins” that Earth and Venus were thought to be, transform in diametrically opposed ways? According to many scientists, billions of years ago, the two celestial bodies had very similar starting conditions – they had comparable climates. There were probably oceans on Venus. Yet in the case of our neighbor, something clearly went wrong. When life flourished on the Blue Planet, her “sister” went off the wrong track at some point, becoming one of the most inhospitable places in the Solar System.
The cause was mainly the greenhouse effect, which was progressing at a furious pace. It’s what put the planet through such torment – it’s closer to the Sun, so it absorbs more of its energy. This alone wouldn’t necessarily spell climatic disaster yet if it weren’t for Venus’ atmosphere. It is characterized by a high content of carbon dioxide (96.5% of its composition), a greenhouse gas derived primarily from volcanic eruptions, as well as toxic clouds of sulfuric acid. Under such conditions, the planet had no chance to cool down.
Any oceans, if they existed at all, therefore had to evaporate. Stephen Hawking claimed that one day a similar story could happen to Earth.
A defenceless planet
All right, but the water that has evaporated from the oceans should still be in the clouds. Water vapor also contributes to the greenhouse effect, but at least there would still be some trace of the chemical that forms the basis of life on Earth. Unfortunately, Venus is cosmically unlucky in this regard as well. In 2005, the ESA-built Venus Express probe detected particles escaping from its atmosphere – most notably hydrogen, a component of water, presumably a remnant of primordial oceans.
The culprit turns out to be the solar wind, against which Venus is unable to defend itself because it rotates too slowly to create an adequate protective shield in the form of a magnetic field (as is the case with Earth). It snatches parts of the upper layers of Venusian atmosphere into space. All the water in the clouds has been systematically ejected into empty space for billions of years, and carbon dioxide takes its place.
To hell and back
Thanks to the launch of many probes, Venus is the best studied planet in our System (apart from Earth, of course). It would seem that such an alien and hostile planet has nothing left to offer us – and yet NASA is devising a plan for a manned mission. Such an expedition was already planned in the 1970s – as part of the Apollo program. After a four-month journey, a group of three astronauts was to fly past Venus at a distance of 5000 kilometers. As we know, nothing came of it.
The current project is called the High Altitude Venus Operational Concept. It does not, of course, provide for a traditional landing on the surface, but to enter orbit and then plunge into the upper layers of the atmosphere, where conditions are most friendly (at an altitude of 50-60 kilometers, the pressure and temperature are actually comparable to Earth’s). If the project comes to fruition and is successful, we will know much more about the “twin”, and thus about the past and possible future of our planet. Perhaps thanks to this knowledge the Earth will manage to avoid a similar fate.
VENUS IN SOME NUMBERS
Diameter: 12,104 km
Mass: 4,867×1024 kg (82% of Earth’s mass)
Year length: 243 Earth days
Daytime temperature: 484°C
Average distance from the Sun: 108 million km
Rotational speed: 6.52 km/h
Moons: Not a single one