Venus is the second planet from the Sun, and the closest planet to the Earth. After the moon and the Sun, it is the brightest thing in the sky. It often looks like a very bright white star shining at night. In fact, if you looked at Venus through a small telescope, you could probably make out different phases of the planet, like what you see in the moon, which is sometimes a full moon, and sometimes only a thin sliver.
In this picture, you can see the Moon in the middle with Venus beside it. Credit: ESO
Earth’s Evil Twin
In other ways, Venus could not be more different than the Earth. The most dramatic difference is the planet’s crushing atmosphere. We usually think of air on Earth as being light and hardly noticeable. But on Venus the air is made up mostly of carbon dioxide, with only small amounts of nitrogen. These gases have created a thick and heavy soup over the planet. They are so heavy, in fact, that they would crush a tin can as flat as a coin if you could somehow drop it on the surface. Standing on the surface of Venus is pretty much the same as standing a kilometer under the surface of the ocean on Earth!
Another effect that has made Venus very different from the Earth, is the incredible temperature on the surface. The temperature reaches an amazing 860 degrees Fahrenheit! This makes the surface of Venus the hottest of any planet in the solar system, even hotter than the surface of Mercury! This is because of all the carbon dioxide in Venus’s atmosphere. Carbon dioxide, or “CO2,” traps the heat from the Sun and from the planet's surface, and keeps most of it from escaping back into space. Some people use this same process to keep plants warm when the outside air temperature is too cold. They put the plants inside a big glass building that lets the sunlight in, but then traps it inside before the heat can bounce back out of the building. This is called a greenhouse, so gases that have this same effect in the atmosphere are called “greenhouse gases.”
Picture of a greenhouse,
where plants are kept warm by putting them under a glass roof that traps the heat from the Sun. A similar process can happen in the atmosphere of a planet, and start to warm the surface to extremely high temperatures.
Carbon dioxide is a powerful greenhouse gas. On Earth animals like humans breathe in oxygen and breathe out carbon dioxide. But there typically isn’t enough in the atmosphere to have an effect like the one that we see on Venus. Some types of pollution, like the exhaust from cars, increase the amount of carbon dioxide in the atmosphere enough to actually start heating the surface of the Earth! Some scientists believe that if we put too much carbon dioxide in the atmosphere, we could start to feel extreme effects on the Earth, like the melting of ice near the poles and temperatures that could hurt some plant or animal life. This process is called “global warming,” and can actually change the air and environment that we are so used to on the surface of the Earth. That is why government agencies like NASA are spending a lot of time observing and measuring the effects of pollution on our atmosphere and making sure that we do not start seeing a drastic change on Earth like the one we see on Venus.
Venus, like the Earth, orbits the Sun at a distance where water can be liquid on its surface. In fact, we think that at a certain point in history, Venus may have had giant oceans on its surface like those on the Earth today. But now the surface of Venus is covered with the remains of volcanoes and what looks like very new surface rock. We can measure the age of rocks on the surface of distant planets using many techniques. For example, we can see how many craters are on the surface of objects in space to understand whether the surface has changed a lot since the last time rocks crashed into that object. Earth’s Moon, for example, is covered with thousands of craters, some of which you can even see at night with your naked eye. This means that the surface has been the same for a long time, since there has been enough time for all these craters to form without getting covered up. On Venus, most of the surface seems very smooth. This makes us think that there may have been a lot of activity on Venus’s surface recently, putting fresh layers of rock on top of any old surface features like craters that may have built up over the years. The surface of Venus is covered in volcanoes. So we think that the volcanoes on Venus may have put a lot of the materials that are in Venus’s atmosphere into the air and also placed lava over the surface, erasing any old surface features on the planet. We also think that because of the extreme process of global warming on Venus’s surface, all of its oceans may have evaporated and the water may have been lost to space, leaving the whole planet dry and scorching hot.
A computer image of Venus’s surface, recreated from real radar information from a NASA mission to the planet.
This is an actual image of the surface of Venus taken by a Russian mission to the planet!
The surface was so hot that the spacecraft was only able to stay cool for about an hour before all its electronics were destroyed, but luckily it was able to take these amazing pictures. This photo has been processed to look like it would actually look on Venus if you could visit and somehow survive. Notice how it is always a little dark out because of the thick, yellow clouds that cover all of Venus’s surface all year round.
Think About It
The only place outside of the Earth that humans have actually visited is the Moon. But we have sent many robotic missions around the solar system, including the amazing one that took the pictures of Venus on this page. We are living during the first time in history that any human has seen pictures of a different planet. So when you look up at the bright dot of Venus in the sky at night, remember that we actually have pictures from the surface of this thing that looks so far away thanks to our robot helpers! But there are many more places that we still have not visited or seen. Maybe you can even make a list of the places we have not yet seen and see if you might be the first person to ever actually see what that place looks like!
Venus is constantly covered in a thick layer of clouds, as you can see in this picture.
When you first hear about Venus’s clouds, it seems like they only make Venus an even worse place to live. With the high pressures and oven-hot temperatures, the clouds of Venus only add to the horror. Some of Venus’s lower clouds are made of pure sulphuric acid! This acid is so dangerous that it could dissolve through metal and would injure any human who touched it!
But higher up in Venus’s clouds, the acid seems to lessen or even disappear, and we start to find big clouds of water vapor, and even temperatures and pressures that are close to Earth. So some scientists think that it is possible for some kinds of life to live high up in these clouds! They even believe that it’s possible that some sorts of extreme organisms, called extremophiles, could possibly live on Venus or in its atmosphere. On Earth, these extremophiles, mostly bacteria, can survive in boiling hot water and even pools of dangerous acid.
Think About It
Living high up in the clouds might seem like a weird idea, but past probes to Venus have found some very interesting puzzles and clues. For example, chemicals like hydrogen sulfide (H2S) and sulfur dioxide (SO2) have been found to exist together in the atmosphere. But if you put these chemicals in the same place, they usually react and disappear! So some scientists believe that this is a sign that something is actually producing these chemicals. We have also found some weird cloud formations that seem to be made out of some mysterious substance. Would you be able to look at clues like this to understand whether there might be life in other places?