Venus to Transit the Sun

On June 5-6, 2012 many of us will have the chance to witness a cosmic event that won’t happen again for another 105 years. On those two days our planetary neighbor, Venus, will pass in front of the Sun. If you’re lucky enough to live in the right part of the globe, and the skies are clear, then you too can be part of space history.  The transit will be visible on June 5th at sunset across all of North America and June 6 at sunrise across most of Europe and Asia.  See the Global Visibility Map at this LINK.

The transit is similar to a solar eclipse—Venus will move between us and the Sun, blocking out some of its light—but there are none of the long shadows and spooky ethereal darkness you get with solar eclipses. Instead, observers (don’t look directly at the Sun) will only see a tiny black dot move across the face of the Sun.

Earth's Evil Twin

But this is no ordinary black dot. Venus is one of the most extraordinary places in the Solar System. The surface temperature on the planet is hot enough to melt lead at 470° C (880° F), and the pressure, of some 90 atmospheres, is roughly equivalent to diving a half mile beneath the ocean on Earth. Venus is surrounded by a toxic soup of gases with sulphuric acid clouds and winds of up to 350km/h (220 mph). This dense atmosphere prevents heat escaping into space—a process often described as a runaway greenhouse effect.

What’s really weird is that Venus is only slightly smaller than the Earth and has a very similar chemical composition and density. The fact that it’s turned out so differently has led those who study the planet to refer to it as ‘Earth’s evil twin.’ 

There have been more than twenty missions to Venus, including two Russian landers, which survived for a couple of hours before getting frazzled by the extreme conditions. The most recent mission, Europe’s Venus Express, is currently in orbit analyzing the planet’s atmosphere. But despite all this international effort, the second planet from the Sun still holds many mysteries.

Cloud city

When we look at Venus we think this is a planet that once, in the very early solar system, might have been very Earth-like. But obviously it changed, it overheated, it turned into the very hot thick atmosphere planet. Nevertheless, when we study Venus we can get a view of the very different ways that a rocky planet like the Earth can evolve.

It seems to be a planet that doesn’t have plate tectonics – but the Earth does – so scientists would like to know why the Earth is so different. We don’t know if it has a very thin crust. . . or maybe it has a very thick crust; there exists evidence of volcanoes but scientists don’t even know if any of them are still active.  In short, Venus contradicts much of what we understand about Earth-sized rocky planets.

There might even be life on Venus despite the fact that it's surface is very hot—and not very hospitable to life—as you go up into the middle atmosphere it becomes very Earth-like.  Some researchers have hypothesized that Venus' middle atmosphere does have life.  About 31 miles (50 km) above the planet’s surface the atmospheric composition and pressure become very Earth-like.