4 June 2010

Solar System Tour: Venus

Posted by Ryan Anderson

Venus is the second planet out from the sun, and is just slightly smaller than Earth. It is 12,102 km across, which is about 95% the size of earth. You can see Venus in the sky in the morning or evening as a very bright “star”. In fact, for a long time it was called the “morning star” or “evenstar”. It is always pretty close to the sun in the sky because it is close to the sun in the solar system. You might think, since it’s about the same size as earth, but is closer to the sun, Venus would be a nice place to live. It would be nice and warm, maybe the whole planet’s a tropical paradise! Let’s go!

You might want to reconsider. Here’s why. About the only thing Venus and the earth have in common is their size. Venus is a really awful place. Try to think of the most unpleasant place imaginable, and I bet Venus is still worse. There’s no water on Venus, but it has a very thick atmosphere. At the surface, the pressure is 92 times the pressure here on earth. The whole planet is covered in clouds (that’s why is shines so brightly in the sky, clouds are pretty reflective). Not just any clouds though. The clouds on venus are made mostly of sulfuric acid. As if that wasn’t bad enough, Venus is the hottest planet in the solar system. That’s right, even hotter than Mercury! The reason for this is the greenhouse effect. The atmosphere on venus is almost all carbon dioxide, the same gas that is causing climate change on earth. What happens in the greenhouse effect is, energy from the sun comes in and then gets trapped by the atmosphere and can’t leave. On venus, the surface temperature is 482 degrees C (900 degrees F!). Unlike mercury, it doesn’t cool down much at night thanks to the blanket of clouds.

For a long time, nobody knew what the surface of venus looked like because all those clouds were in the way. Luckily, radar came to the rescue. Radio waves can go through the clouds easily. Radar works by sending out a bunch of radio waves, and then measuring how much gets reflected back. Several probes have been to Venus, and almost the whole surface has been mapped using radar. Here’s what it looks like underneath the clouds.

Venus has a structure similar to earth. It has an atmosphere, and a thin crust. Unlike earth, venus’ crust is probably all in one piece rather than broken into separate plates. Below the crust is a rocky mantle, and a metallic core. Scientists aren’t sure whether the core on venus is solid or not, but it is probably about the same size as earth’s core, about 6000 km across.

You might notice that, compared to mercury, venus has hardly any craters. Part of this is because of the very thick atmosphere. Stuff just burns up before it hits the ground. That’s not enough though. The lack of craters means that venus is geologically active, so its surface is pretty young. Venus has a lot of volcanic activity, 85% of its surface is covered with volcanic rock. There are huge lava flows hundreds of miles long and large plains created when lava filled low-lying areas. There are more than 100,000 small volcanoes and hundreds of large ones. The radar image below is of Sapas Mons, which is a very big volcano (250 miles across and a mile high). You can see lots of lava flows coming out from the center. They look bright because rough surfaces scatter radar waves better than smooth surfaces.

Here’s an example of some of the thousands of smaller volcanoes. Each little bump in the picture is a volcano.

Here are four “pancake” volcanoes. They form when thick lava oozes up from below onto level ground, and just expands in all directions.

You might think that, being such a nasty place, there’s no way we could ever land anything on venus. Believe it or not, the Russian space program put 10 landers on the planet between 1975 and 1982. They were called the Venera landers. Venera 13 lasted the longest: 2 hours, 7 minutes. It managed to take 14 pictures. Here’s what the surface of Venus looks like:

The pictures look distorted because of the type of lens used by the lander’s camera. The upper left and right corners show little patches of the sky. You can see part of the lander at the bottom, and the thing on the ground in the left picture is the camera’s lens cap. The rocks look like basalt, a volcanic rock found on earth.

All in all, venus is not a nice place to be. It looks nice enough shining in the morning sky, but it just stands as another reminder that looks can be deceiving. In the future we will send more probes, but the chances are very slim that people will ever walk on its deadly surface.

Check out the previous posts in the Solar System Tour:

Solar System Overview

The Sun