February 2015 Script – From Venus, With Love
FROM VENUS, WITH LOVE
Hello, I’m Darrell Heath with the UALR College of Arts, Letters, and Sciences, welcome to The Night Sky.
When I was a boy of about 10 or 11 I became hooked on Edgar Rice Burroughs’ John Carter of Mars novels. For weeks on end I stuffed my head on these planetary science fiction adventures and craving more I then turned to his Carson of Venus novels. Burroughs had a tendency to recycle his plots but I didn’t care, I just wanted more wild adventure stories that took place on other planets.
Whereas his version of Mars was that of a dry and dying world inhabited by an assortment of exotic aliens and creatures, his Venus was that of a tropical paradise. According to Burroughs, Venus was a planet enshrouded by water-laden clouds and beneath those clouds was a world that was mostly ocean with a few landmasses covered in jungle. What’s more there were giant reptiles aplenty and for a boy who was also in love with dinosaurs Venus seemed like the place for me.
On paper Venus and Earth do appear to be twin sisters of one another: both are very similar in size and mass with Venus being just a bit smaller, both have a similar surface gravity, and both possess substantial atmospheres and even clouds. But there the similarities end. As most of you already know the planet named for the goddess of love is downright nasty.
Orbiting spacecraft using ground penetrating radar as well a probes sent to the surface reveals a world more akin to Hell than paradise. Venus’ surface temperature is a scorching 860 degrees Fahrenheit. That’s hot enough to melt lead! The atmosphere is so thick that were you able to reach the surface you would be crushed under pressure that is over 90 times what you experience here on Earth. The Venusian atmosphere is mostly carbon dioxide and those clouds that perpetually enshroud the planet are not made of water vapor but are instead composed of sulfuric acid. No oceans of liquid water cover Venus; its surface is a desolate landscape of scorched rock and thousands of dormant volcanoes.
But was Venus always this way and if not then what made it so inhospitable?
Many astronomers believe that during the first 2 billion years of its history Venus may well have contained oceans of liquid water. In fact, it was this water that eventually led to the planet becoming the hellish world we know today. But the instigator for the transition from paradise to Hell wasn’t the planet but the Sun.
Like any star our Sun has undergone changes during its 4.5 billion year history and will undergo more changes in the distant future. Early on in its life the Sun was much dimmer and cooler than it is today and during this time Venus was on the edge of the habitable zone at around 67 million miles away. But at around 2.5 billion years ago the Sun began to brighten and became much warmer.
Being much closer than the Earth is to the Sun Venus began to warm up and its water began to evaporate to form a thick cloud layer that enshrouded the planet. Water vapor is a potent greenhouse gas so, while sunlight was allowed to penetrate the cloud layer, the much longer wavelength of infrared heat energy was prevented from escaping. This made Venus even hotter and even more water vapor entered the atmosphere. The result was a runaway greenhouse effect. Eventually the surface became so hot that carbon was baked out of the rocks, which then entered the atmosphere to create carbon dioxide, another powerful greenhouse gas. Venus’ fate was sealed and all the water on the surface boiled away. Today we can find only traces of water in the atmosphere, the rest has escaped out into space.
In a surprise twist space probes have discovered that at about 31 to 40 miles above the surface there exist conditions that are remarkably Earth-like, in fact you will not find such hospitable conditions anywhere else in the solar system. At these altitudes the atmosphere is actually breathable with a mixture of 21% oxygen and 78% nitrogen. But if you plan to visit be sure and bring along the air conditioner because temperatures are at around 167 degrees Fahrenheit.
While human induced global warming will most likely not create conditions as extreme as those on Venus the planet still serves as a stark reminder of the dangers of dumping excess greenhouse gases into our own atmosphere. Even a fraction of those conditions will have devastating consequences for life on Earth.
Whenever Venus is visible in our morning or evening sky it is often the brightest object visible outside of the Moon. All this month you can spot the second planet from the Sun quite easily during the hours of dusk just around and after sunset low along the western horizon. Be sure and look for the much fainter planet, Mars, next to it. Early on in the month Mars will lie about 8 degrees above Venus but as the month wears on they will get closer and closer together. On the nights of February 20th through the 23rd the two are less than one degree apart, a close pairing indeed! On the 21st they are actually a half a degree apart and what’s more we will have a very lovely crescent moon that will be part of the western sky view as well. When Venus and Mars are that close you will need either binoculars or a small telescope to split them apart optically. Now, keep in mind that even though they are close together on the sky they are in fact separated by millions of miles in space.
That’s all for now but be sure and visit our web site for more astronomy news and information. Until next time be sure and get outside to look up and wonder.