Settle The Stars – Venus
Hello folks, this is Alexander Winn.
In this episode we’ll be visiting Venus, our nearest neighbor and one of the most-watched objects in our sky throughout the ages. In our journey we’ll learn about some of the strangest and fiercest conditions our Solar System has to offer: scorching heat, crushing pressure, dueling hurricanes and acid rain. We’ll find out the latest in the search for alien life in this hellscape and learn about the pivotal role Venus has played in some of the most important discoveries in history and the important lessons she continues to teach us about our own home on Earth.
To us here on Earth, Venus is not some faraway, unknown world. When we think about it, we don’t need some special mnemonic device as we would to remember the moons of Saturn or a special code designation like we use for the many comets buzzing around the Sun. It’s right there in the sky, a familiar bright star clearly visible from just about everywhere on Earth. In fact, before you even knew what a planet was, you might have even wished upon it with the popular poem: “Star light, star bright, first star I see tonight…” As the brightest object in the sky after the Sun and Moon, it’s no wonder at all that Venus has captured our attention the way it has.
Throughout history Venus has been a subject of interest and inspiration for us here on Earth. Because Venus is closer to the Sun than us, it never strays far from it in the sky – which explains why it is visible in the morning or evening when the Sun is just below the horizon. It also follows a synodic cycle in which the planet becomes invisible as it gets near the Sun, and then appears again on the opposite horizon on the other side of the Sun. During this cycle, the planet can be observed quite high in the sky, but never quite reaches the apex. These interesting features stirred the imaginations of early stargazers, who told stories about the gods and goddesses they attributed to Venus as a way to illustrate and explain these observations.
The disappearing act Venus plays, visible for a time in the morning and then switching to the evening as the planet passes Earth in its orbit, was of intense interest to many ancient cultures. Many interpreted the phenomenon as an illustration of a god with two balanced aspects or explained the temporary disappearance (which lasted about three days) as a divine journey to the underworld.
The ancient Mesopotamians who lived where Iraq is today named the planet Inanna after the goddess of love and war – balanced aspects of life and death. They recorded stories of Inanna’s journey into the underworld, her death and rebirth, to explain the disappearance of the planet from the sky. In fact, many details of Inanna’s saga, from her journey to Kur, or the mountains of the West, to a heavenly search for her enemy can be linked to the movements of Venus in the sky.
Across the globe in Vietnam, ancient stargazers believed the morning star and evening star were two separate entities. Folklore tells the story of two separated lover stars, sao Mai and sao Hôm, destined to search for each other and remain apart forever.
In classical Roman mythology, Venus was known as “Lucifer”, or “Light-Bringer” in Latin, in the morning and Vesper in the evening. This mythology carried over into Christian stories of a fallen angel who was punished for attempting to climb too high within heaven, another link to Venus’ path which approaches – but never quite reaches – the apex of the sky. Ancient myth about the planet was adopted elsewhere by Christians, appearing again in the book of Revelation, in which Jesus refers to himself as the “bright morning star”. Interestingly, according to the story Jesus eventually undergoes his own three-day period of death and rebirth celebrated annually as Easter.
Perhaps no culture was as intensely devoted to Venus than the Mayans. To the Mayans, Venus was known as Chac ek, “The Great Star”. To the Mayans, Chak ek was the most important celestial body – even more so than the Sun and Moon. Their calendars meticulously recorded the movement of the planet and predicted its activity over a period of thousands of years, accurate to within the hundredth part of a day. The Mayans believed Chac ek influenced the activities and quality of life on Earth, and all major events within the empire – including war – were carefully timed to coincide with the position of the planet.
All these cultures and societies all over the world – too many to mention – were enthralled by this mysterious Morning Star and the mysterious order of her movement across the sky. By observing, tracking and recording Venus and the other planets as meticulously as they did, a general understanding and appreciation emerged for astronomy. This in turn advanced our understanding of the physics, optics, mathematics and geometry necessary to successfully observe the stars, leading to even more discoveries.
More recently, Venus contributed to Europe’s domination of the globe during the age of exploration. Back in the 1700’s the seafaring nations were busy colonizing, waging war and trading all around the world. But even with their new expertise and expensive warships, a seemingly simple question of navigation confounded them: How can a sailor accurately measure his location on the planet independently? How far north or south of the equator a navigator is – or latitude – can be identified relatively easily by measuring the angle of the Sun at noon. But identifying location longitudinally, or how far east or west one has travelled, is a much more difficult problem that led to some tragic and embarrassing shipwrecks at the time.
It was believed that having an exact measurement for all these relevant navigational references – the distance from Earth to the Sun, the distance to the planets, and the size of the Earth itself would contribute to a solution and provide an answer to the question of navigation. And as it happened, a rare astronomical event – the transit of Venus – would provide an opportunity to provide that information.
The transit of Venus is the name for the special alignment of the Sun, Venus and Earth. An observer here on Earth can witness Venus as it transits – or travels – across the face of the Sun. Astronomers at the time realized that by timing the length of time it takes for Venus to pass between the Earth and Sun from various vantage points across the globe, all kinds of measurements could be calculated: the size of the Sun, Venus and Earth, for starters – as well as the distances between each of them.
The scientists realized they would only get two shots at this, because transits of Venus are a once-in-a-lifetime event. The orbital cycles produce a pair of transits eight years apart about every century, so expeditions were prepared around the world in one of the first international scientific endeavors to record the transits in 1761 and 1768.
The transit of Venus in 1761 was an excellent trial run. The expeditions included a new team of astronomer Charles Mason and surveyor Jeremiah Dixon, whose excellent observations would make them famous enough to be called to settle a land dispute in North America by establishing the historic Mason-Dixon Line.
But the second transit in 1768 was the main event, with observers sent from the arctic circle to the south Pacific. A special scientific commission from King George III placed Lt. Captain James Cook in command of the Endeavor to lead the expedition to Tahiti. After a successful observation of the transit from the southern islands, Captain Cook steered his ship westward to eventually reach the mythical Terra Australis Incognita and claim the continent now known as Australia for the British Empire.
So, we see how even as an object of curiosity and inquiry, Venus has played a major role in the shaping of our collective human history. Major advances in the study of physics, astronomy and mathematics were made in our attempt to better understand the planet and how it related to our own.
Over the centuries as telescopes became more advanced we would observe that the entire planet is permanently engulfed in thick clouds, spurring imaginative theories and fictions of advanced civilizations living and breathing just like us.
Once we got a closer look with the help of satellites and probes, we realized how unlikely that was. Since 1961, 42 missions have been attempted to explore Venus, with the first successful flyby in 1962 by NASA’s Mariner 2 probe. The first ever successful human landing on another planet was achieved by the Soviet Venera 8 lander in 1972. While the data returned from Venera 8 was limited, subsequent landings and flybys painted the picture of a planet far different from the beckoning and jubilant morning star celebrated by so many cultures around the world.
These early observations depicted a hellscape. An atmosphere dense enough to crush a steel craft raged in a perpetual tempest at the poles, and where scientists hoped clouds might offer life-giving rain almost no trace of water was found. Instead, corrosive sulfuric acid was found in abundance, with the toxic liquid actually raining down from the sky at higher altitudes. And across every surface, infused in every gust of caustic wind, was an astonishingly intense heat.
It became clear that any life here would be having a rough time of it. By the 1970s it was clear that complex life on the planet would not be viable, but scientific debate continues even today on whether the atmosphere might support colonies of extreme bacteria or similar organisms. Evidence for life continues to be sought within the data and spectrophotometric data collected so far, but definitive confirmation will hopefully be provided by one of the 15 future missions currently being developed by various agencies worldwide.
So, what does all this mean for potential human exploration? How would an explorer experience these conditions firsthand? By compiling our observations so far we can make a rather good guess.
Step one for many explorers will probably be to say goodbye to friends and loved ones – doubly so for the first visitor to a world as dangerous as Venus. Not necessarily because it is a suicide mission – scientists and engineers will do their best to keep you safe – but because early manned voyages probably won’t come with a return ticket. Fuel and repairs are tough to come by without infrastructure, and the thick atmosphere of Venus will require an immense amount of thrust to relinquish any craft back to open space. So, the first explorers will probably become permanent residents to pave the way for future visits.
Fortunately, Venus is close, a mere 24.8 million miles at its closest, but it’s never a straight shot between orbiting planets. The quickest trip to Venus so far was accomplished by Mariner 2 in 1962 which spent 109 days en route. It’s probably safe to assume a trip will take around 120 to 130 days, or 4 months. In terms of space travel, that’s a quick commute. If you manage a full night’s rest all along the way you’d be left with about 2,000 hours’ worth of time to kill. Assuming any interplanetary explorer worth their salt is a fan of Star Wars, you’d have enough time to watch the full series of 11 live-action movies only 80 times or so before it was time to land.
But sadly, you probably wouldn’t get the chance to make it through that many. Your waking hours will more likely be filled with exercise to keep your muscles and bones strong as they become accustomed to weightlessness, patching up the occasional damage caused by a stray piece of debris or conducting experiments to make future long-term space travel easier for future explorers. So maybe you’d only get to see Star Wars 30 or 40 times. Bummer, I know. But the real work begins once Venus is in view.
The first task will be determining a final position to bring the spacecraft in for landing. Beneath the clouds the surface is generally rocky and uneven just about everywhere, so the main consideration will be weather. The clouds will obscure your view of the sky anywhere on the planet, but the equator offers less wind which is no small concession. As far from the poles as you can get is usually where you want to be on Venus.
Scientists were mystified to discover that both the north and south poles of Venus are crowned by intense storms unlike anything they’ve seen before. At each pole swirls a violent double vortex, each of which churns like two hurricanes here on Earth circling around each other. The south pole has been better observed, where the combined size of this huge storm is estimated to be as large as Europe with wind speeds of over 300 kilometers per hour. Most of the wind at surface level is composed of carbon dioxide, which makes up 96.5% of the atmosphere, and most of the rest is nitrogen. That means the air is much, much heavier than here on Earth – about 50 times as dense. So, if 300 kilometer-an-hour winds doesn’t sound all that bad to you, remember that it packs a much heavier punch.
If it’s all the same to you, I suggest we land closer to the equator where wind speeds are usually down to about 5 km/hr. Our landing module will be reinforced like a submarine to counter the intense pressure of the atmosphere as we descend. Even just alighting atop a hill on the surface of Venus is the pressure equivalent of diving 3,000 feet underwater here on Earth. Admittedly, most submarines on Earth aren’t bathed in sulfuric acid before they carry people deep underwater, but unfortunately there’s no way around it here on Venus. The thick clouds covering the planet are almost entirely composed of the corrosive acid, so our lander will have to be well protected to ensure we continue to withstand the pressure and heat as we descend. And boy, is it hot. Venus has the hottest temperatures in the Solar System outside of the Sun, thanks to that thick blanket of clouds. Our poor landing module will also need to protect us from temperatures hot enough to melt lead, around 880 degrees Fahrenheit (that’s 470 Celsius). At least we won’t get zapped by lightning. Probably. The clouds do appear capable of producing lightning like on Earth, no strikes have been observed directly yet so if it does occur it’s likely pretty rare. So that’s good.
But here we are at last, safe and sound on our own little slice of paradise – we survived the wind, the acid clouds, the scorching heat and the crushing pressure. Now what?
I don’t think a little sightseeing would be out of the question, we did just travel quite a long way after all. But if you’re waiting to see what a sunset looks like beneath the churning clouds of Venus, you might be waiting a while. A single day on Venus is as long as 243 days on Earth – that’s the slowest rotation in our solar system by a long way. And not that it will make much of a difference from under the acidic haze, but the Sun will actually set, very slowly, into the eastern horizon instead of the west.
There won’t be different seasons to speak of like we’re used to on Earth, so no need to plan a different outfit for the springtime – you’ll find your ultraprotective suit to be conveniently stylish year-round here. A supercritical sea of carbon dioxide at ground level would probably make walking outside feel like you’re trudging along underwater, but at least the thick atmosphere will keep us as cozy as a pot in a kiln throughout the long night. On second thought, it’s probably best to get back inside.
Safe within our surface submersible we can turn our attention to observation and experimentation, to attempt to unravel some of the other grand mysteries Venus still holds.
For starters, as we look up into the toxic, roiling clouds: how has the atmosphere changed into this incredibly hostile state? There are a lot of unexpected peculiarities about Venus’ sky for us to consider, for example its composition – for being so similar to Earth in size, composition and location, the air of Venus is highly enriched with noble gasses as compared with Earth. Does this hint that the planets formed from very different primordial nebula compositions, despite their proximity? Or perhaps a large comet impact delivered the gasses in some past collision? There are likely many clues to be found within the craters and rocks of the planet to help support or discount these theories.
What’s going on beneath our feet, anyway? What lessons can we learn about volcanism and plate tectonics? What evidence can we find beneath the clouds that are impossible for our telescopes and probes to see from above? It is clear that volcanoes once covered the landscape – in fact, there are many times more volcanoes on the surface of Venus than Earth, and many of them are larger than the largest here on Earth. But are any of them still active? Perhaps this is explained by the fact that without the continuous recycling of crust that the Earth undergoes, the Venusian volcanoes simply last longer, shielded from erosion and impacts by the thick atmosphere?
Erosion does seem to work differently on Venus. On the occasion that an object manages to punch through the thick Venusian clouds, it makes a crater just like you would expect. On Earth, such craters are worn down by wind and rain, and on a world with no atmosphere the craters are gradually erased by… other craters. But most of the craters on Venus appear to be in pristine condition.
Paired with the high number of well-preserved but quiet volcano calderas, these observations support a prominent theory that Venus underwent a globally catastrophic resurfacing event sometime around 300 to 600 million years ago. Perhaps in contrast to Earth’s gigantic conveyor belts of crust being generated and subducted, Venus alternates between long periods of geologic calm, gradually building temperature and pressure until everything is released in a massive, planet-wide eruption. Perhaps a quick escape pod would be a good idea after all…
And speaking of erosion, where has all the water gone? With such an abundance on nearby Earth, surely there would be traces on our twin world. One hint lies in one curious detail: Venus lacks a large internally generated magnetic field like the one Earth has. Instead, it’s much weaker magnetic field is induced as an interaction between the outer ionosphere as it collides with the solar wind from the sun as opposed to an internal dynamo generated by convection currents in the mantle. Not only is this more evidence that the internal workings of the planet differ from Earth’s, but also helps explain the lack of water: as the heat of Venus rose and water evaporated, it was gradually blown away by the solar wind without a protective magnetic field.
There are many differences between the Earth and Venus, but from the perspective of organisms living on a planet currently undergoing rapid climate change, the lessons from Venus are invaluable. Evidence shows that in the past Venus was likely quite different, with global, permanent changes to the characteristics of the planet imposed by a drastic runaway greenhouse effect. Whether the effect was initiated by some specific geologic event or gradually snowballed as a natural progression from its initial composition is still in question, but the very real and profoundly serious effects of these processes is well worth our study. We could learn more about the forces at work in our environment on Earth, helping us prepare for new challenges or warning us of the catastrophic consequences of our actions.
To encourage future expeditions to the planet, it will fall to us as the first explorers on Venus to make sure the adventurers to follow find more comfort and access than our little shelter can provide.
One promising idea is to take advantage of the thick Venusian air and sail atop it in a great airship instead of sheltering on the surface. A container of air as we would find it on Earth would be quite buoyant indeed on Venus, which has caused some engineers to envision entire colonies – or even cities – of humans floating above the clouds to continue study of the planet from above.
A valuable takeaway from our visit to Venus is that even after the dozens of successful probe and lander missions, centuries of observation from telescopes, an impressive array of sensors and massive amounts of data, our nearest and most similar neighbor still holds so many questions to be answered. Next to the farthest and strangest space anomalies detectable from Earth, it can seem like the book on Venus has been written and closed already – but nothing could be further from the truth.
We hope you enjoyed our visit to our sister planet today and learned some interesting facts to feed your curiosity about this mysterious planet. We’ll be continuing our journey next week to another familiar destination with another personal interplanetary tour – this time of the Red Planet, Mars.