If you have ever looked up at the night sky, you must have seen the planet. Being the third brightest object in our sky after the sun and the moon, it’s pretty hard to miss. Speaking of the moon, this planet has no natural satellite of its own. The planet got its name from the Roman goddess of love and beauty, quite apt indeed. Venus, the second closest planet to our sun in the solar system, is often referred to as Earth’s twin due to its identical shape and size. Yet, there are significant differences between the two. The most obvious one is the environment on Venus which is non-conducive for life (as far as we know it yet!). The rotational direction of Venus is opposite to all the other planets in the solar system except Uranus, which shares the common event of the sun rising in the West and setting down in the East. The length of a day on Venus is equivalent to around 117 Earth days (synodic, 243 days if you wish to count sidereal), making it the planet with the longest duration of a day. Venus is the closest a planet can get to Earth, but it doesn’t stay that way for long because of its orbit. Venus is a mere (at the cosmic scale) 40 million km away from the Earth at its closest, while the farthest it can get, on the other side of the sun, is roughly 260 million km. While the orbit of other planets is elliptical, the orbit of Venus is the closest we have to a circular one. With an eccentricity of much less than 1, it is indeed the closest in our solar system.

Chemical Buildup and Weather and Surface


Artistic Impression of the Venusian Surface, ¹

The atmosphere of Venus is highly dense, one of the densest the astronomers have encountered. The thickest amongst the inner rocky planets. Over 96% of it consists of only carbon dioxide, and the rest contain nitrogen and minute traces of other gases primarily. Due to the extreme density, the atmospheric pressure on the surface is 92 times the Earth’s atmospheric pressure. Unimaginably high pressure for a rather small planet. To give an idea, the same pressure on Earth would have been at around 900m below the sea surface. The best human divers with the most advanced equipment have only reached a depth of around 40m only. As if the extreme pressure weren’t enough, it is also the hottest planet. It is primarily because of its atmosphere, which, unlike Mercury (which logically should have been the hottest planet), doesn’t let the heat escape. Something similar to the greenhouse effect we have here on Earth, except it’s more intense on Venus. Because of exceptionally high concentrations of gases such as carbon dioxide, it traps heat more effectively. It prevents any heat or thermal radiation from escaping. This phenomenon is what we call a runaway greenhouse effect. The mean temperature of the planet is approximately 460 degrees Celsius. The temperature is high enough to melt various metals, such as lead, tin, zinc and a variety of aluminium alloys; The Venusian atmosphere has an opaque layer of sulphuric clouds. This layer is quite crucial to understanding why Venus is the way it is. These clouds are highly reflective and help trap heat. The Earth’s axis has a tilt of 23.5 degrees. This tilt is what causes the seasons on Earth. The axis of Venus is around 3 degrees only, eliminating any possibility of changing seasons and consequently eliminating any factors to mediate the extreme climate of the planet. Moreover, a particular side of Venus continually receives sunlight for roughly 58 days straight. The climate on the planet overall is one of the harshest in the solar system. The surface is regarded as isothermal, meaning the same temperature everywhere. No noticeable change in temperature can be observed on the surface as we move. The only way to cool yourself, if you somehow happen to find yourself on the surface, and if not already crushed by the atmosphere, would be to move up as high as possible. Altitude has a direct effect on temperature. The higher we rise, the cooler it gets, though still not nearly cool enough by human standards. Wind systems on the planet distribute heat throughout the surface. Thus no difference can be observed in the two hemispheres and between pole and equator. Various missions to Venus have used surface radar mapping. It has mainly been determined that the surface is riddled with craters, mountains, active volcanoes, and lava flow plains. The volcanoes are believed to be active. All the rocky planets in the solar system are riddled with craters, our Earth included. A general trend has been observed in these craters. Smaller meteorites are much more likely to strike a planet than larger ones. As a direct consequence, the number of smaller craters is greater than the larger ones. Venus has a uniquely observed trend, though. No crater smaller than about 1.5 km has been observed on the Venusian surface—a rather peculiar thing to note.

Possibility of Life

One distinct thing that astronomers always note is the striking similarity between Venus and Earth. “The Twin Sisters’’ they are called and quite rightly so. The internal structure, density, shape, and size are all very similar to our home planet. Both planets boast of a complex weather system. They are believed to have a common point of origin back in the past, around 4.5 billion years ago. Yet, the two planets diverged and developed differently enough for one planet to support life at a certain point in time. At the same time, the other was a literal microwave. Our Earth’s outer core is essentially liquid metal rotating in the direction opposite to Earth’s rotation, creating a dynamo effect that gives Earth its distinct magnetosphere. With Venus, this is not the case. It lacks its own “active” magnetic field and instead has an induced one, which is quite interesting. Almost like a coil of wire in an electromagnet would induce a magnetic field in the iron core. Like Earth, the upper atmosphere, with no existing magnetic shielding, interacts with incoming solar radiation and gets ionized to form an ionosphere. The same happens on Earth, though on a much lesser scale. This ionosphere then can partially deflect the radiation. The Earth’s and Venus’s magnetosphere are different in shape, as shown by the figure below.


Magnetospheres of the Respective Planets, ²

It is possible Venus had water in the past. But if it did have any, the high temperature would have vapourised it all. A widely accepted theory also states that solar radiation might have photodissociation in the water due to the lack of planetary magnetic field. The hydrogen gas so formed would have been carried into space via these radiations. It is crucial to mention that to date, astrobiologists have found no proof of life. The current environment is quite extreme for any life to survive. While the water might have been present in the past, nothing yet indicates life thriving on the planet in the past. If it is assumed the water was present on Venus in the past, it would have been during the period shortly after the Late Heavy Bombardment, corresponding to the Neohadean and Eoarchean eras of Earth. All these, however, are speculations, or a better way to put it would be our best guess based on the limited information available on the planet. This data has been primarily collected via radar mapping of the Venusian surface. Very little information is known about the surface because landers cannot survive the extreme heat and pressure to collect vital data and send it back. The USSR’s Venera missions are the most prominent surface missions. Venera 7 was the first to land, followed by a host of other Venera and the Vegas missions. Of the 30 successful missions launched by us involving Venus, only 8 of them had landers that were launched towards the surface.


First pictures of Venetian Surface from Venera 13, ³

The longest a lander has lasted on the Venusian surface is about two hours—far less time to transmit vital information about the planet. Sending a lander to the surface is expensive and troublesome. Most prefer the easier and more logically way of studying the planet – Artificial satellites orbiting the planet, far beyond the reach of its destructive environment. Yet, much more information lies on the surface, waiting to be studied, to be explored. Perhaps it would be considered a pinnacle of human ingenuity and marvel of engineering to be able to put a stable lander on the planet – fighting against all odds for its survival, and at the same time studying the very planet which is trying so hard to destroy it. Perhaps with enough perseverance, one might also put humans on Venus. Or, for that matter of fact, anywhere in the known universe. All it takes is a determined person curious enough to explore the known boundaries of the universe. Sure there will be setbacks, failures, disappointment. Spirits may break, but as long the faith in our ability remains, we will succeed someday or the other. We have come this far, and we would continue to venture further, both into the future and space.

Spock would have been proud.

So long, and thanks for all the fish!

Image from Air and Space Magazine.com ↩
Image from Planet X News ↩
Image from Astronomy ↩