How does it rain Diamonds on Uranus and Neptune?

 Concept of Diamond Rains

Just like it rains water on the Earth, it rains Diamonds on Uranus and Neptune. Yes, you heard it right! As you know, the four outer planets are all gas giants. Meaning, they are made up of gas and are held together by a rock and metal core. Their atmosphere mainly consists of water, methane, and ammonia.  The clouds of methane and ammonia are the ones that are visible from the earth when we look at these planets. Now that you have a basic understanding of how these planets are, let us move on to the interesting part. 

As I've said earlier, these planets are gas giants, which means they are tens of times bigger than earth. This suggests that there have to be many layers of atmosphere surrounding the core. Above that, literally, the atmospheric layers are made up of methane and ammonia, which are very dense. This adds extra weight and that's why the atmospheric pressure increases tremendously. For example, the atmospheric pressure on Jupiter is so dense that if we send a normal spaceship into Jupiter, it will be crushed. This could also be owing to the massive storms that keep raging on Jupiter. 

On planets like Saturn, Uranus, and Neptune, there are minor storms. The lightning from these storms transforms methane into huge clouds of soot. As we go towards the center, the pressure increases so much that these chunks of soot are likely transformed into diamonds. This results in Diamond rains on the planet. 

However, as they fall further down towards the core, these diamonds liquify. 40,000 km down, the pressures are so intense, gases behave like liquid metal. It’s like molten helium falls like rain through hydrogen and releases an incredible amount of heat. Basically, this is the heat source that drives the weather of these planets.

Let me tell you how diamonds are formed on the earth so that you will get an idea of how much pressure the atmosphere of Uranus and Neptune have. On the Earth, when there is a volcanic eruption, the molten lava comes to the surface and hardens. This hardened rock is called Igneous rock. When water and minerals precipitate them, they turn into sedimentary rocks. As new sedimentary rocks keep forming on top of each other because of new volcanic activity, the older layers keep getting pressed down. After millions of years of this repeated cycle, the deep layers of sedimentary rocks change their shape and properties due to the intense, hot temperature they are subjected to. They get converted into Metamorphic rocks. The pressure becomes so high that carbon in these rocks is pressed down and diamonds are formed. Keep in mind that diamonds take millions of years to form and that's why they are so expensive. Such intense pressure is present in the atmosphere of Saturn, Uranus, and Neptune.