Last Updated On: January 15, 2021

What is Uranus’s atmosphere made of?

The seventh planet from the sun, Uranus, is the third-largest in size and fourth largest in mass out of all the planets in our solar system. Unlike the larger “gas giant” planets like Jupiter and Saturn, Uranus is often referred to as an “ice giant.”

It means that its atmosphere is primarily made up of hydrogen and helium, but it also contains heavier materials or “ices” like methane, water, and ammonia.

Uranus has a dynamic atmosphere. Hubble.

While Uranus’s atmosphere is much colder and contains more ice when compared to other planets, it is still made up almost entirely of cold swirling gases like hydrogen and helium.

Hydrogen

Hydrogen is the most common element in the universe, so it should come as no surprise that it’s also the most common element found in Uranus’s atmosphere.

Hydrogen gas tends to have a green, greenish-blue, or gray tint, but only in very high concentrations.

The gas is non-toxic but extremely combustive. Hydrogen forms bonds with other compounds exceptionally easily, so it’s usually found in combination with other gases, including helium and other nonmetallic elements.

Helium

Helium is the second lightest and second most common element in the universe, second only to hydrogen. When the hydrogen in stars undergoes nuclear fusion, helium is one of the byproducts.

Most of us know helium for its voice-changing properties, but it’s responsible for making up a large part of Uranus’s atmosphere.

If you run an electric current through a collection of helium gas, it will give off an orange or yellowish glow, but otherwise, it is gray or mostly colorless. Most helium on Earth comes from natural gas reserves found in the Southwest states of the US.

Methane

Methane is yet another too abundant compound that is most well known for its use as a fuel here on Earth. In space, however, methane makes up around 2.3% of Uranus’s atmosphere.

It may not sound like a lot, but it’s nearly thirty times as much methane as is found in the sun. Unlike helium and hydrogen, methane isn’t a gas.

Instead, it’s a mix of four hydrogen atoms and one carbon atom. Technically, methane is a “volatile”, which means that it can very easily be vaporized, but is far more often found in its liquid or frozen states.

Other Compounds

In addition to methane, helium, and hydrogen, Uranus’s atmosphere contains water, ammonia, and hydrogen sulfide. In general, the deeper into Uranus’s atmosphere one looks, the denser the materials that make it up become.

Methane, water, ammonia, and hydrogen sulfide are all found in the lower layers, while hydrogen and helium make up the upper layers.

Beyond a certain depth, most of our knowledge of the atmosphere’s composition is speculative, which means that we don’t know the concentrations for most of these compounds.

Since the 1990s, however, we’ve been learning more and more about each new layer’s specific breakdown.

So Why Is Uranus Blue?

Uranus drawing

At the most basic level, Uranus is blue because of the light it reflects. The mix of gases and volatile compounds on its upper and lower levels absorb many red, orange, and yellow waves of light.

The blue and green wavelengths, on the other hand, are bounced back. The light any planet reflects is due in large part to the gases that make up its atmosphere.

In this case, the hydrogen, helium, and methane compounds on the atmosphere’s outermost layers absorb the reddish-orange light from the sun’s rays while reflecting the bluish-green light. 

Fun Facts

Uranus was the first planet to be discovered in modern times

Ancient civilizations had already discovered six out of the eight planets we know today, but Uranus and Neptune are too dim to be seen with the naked eye.

It wasn’t until 1781 when William Herschel saw what he thought might be a large, slowly-revolving star through his telescope that Uranus was first observed!

It took several more years for his contemporaries to decide whether the celestial body was a planet or a star. Still, they ultimately realized that it followed an orbit and was, therefore, a planet.

Uranus is the only planet to be named after a Greek god

All of the other planets take their name from the Roman pantheon. If Uranus were to follow that model, it would be “Caelus,” the Roman name for the father of Jupiter, or Zeus.

However, Johann Bode, the astronomer who first observed the planet’s orbit and chose its name, didn’t like the way “Caelus” sounded. As a result, Uranus stands out from the rest of the solar system with its uniquely Greek name in the middle of a bunch of Latin or Roman planetary names.

Uranus has twenty-seven moons

Eclipse in Uranus

These moons are divided into three groups: the thirteen inner moons, five major moons, and nine irregular moons. The inner moons are small and dark and made of similar materials as Uranus’s rings.

The major moons are more advanced, with canyons and volcanoes on their surfaces. The irregular moons are more elongated, usually elliptical in shape.

The first two moons discovered were named after the Shakespearean air spirits Titania and Oberon, and the next two after Alexander Pope’s fairy tale characters, Ariel and Umbriel. Since then, most of the names have come from Shakespeare.

Uranus orbits the sun once every 84 years (by Earth standards) 

While it takes 84 years to orbit the sun, the seasons aren’t quite the same. Instead, Uranus gets about 42 years of summer sunlight at a time, followed by four years of winter darkness.

It isn’t as warm as it might sound, as the sunlight that reaches Uranus is only about 1/400th as intense as it is during our summer on Earth.

This distance can be explained by the fact that Uranus is at least 2.5 billion kilometers from the Sun or 1.7 billion miles.

This fact was mentioned briefly above, but Uranus has rings, too! They may not be as clearly visible as Saturn’s, but Uranus has nine rings around its main body.

Each ring is only a few kilometers in width, which might explain why they’re so rarely depicted, but they’re opaque and made of dust and other space debris.

There are some dust bands and incomplete arcs of debris between the rings, but only nine complete loops.

The rings are relatively young, especially compared to rings on other planets, and humans didn’t observe them until 1977.

Uranus is considered the “most boring” planet in the solar system

The Voyager spaceship passing by Uranus

It isn’t so much a judgment as it is a lack of observation.

Because it has a relatively calm atmosphere and is so challenging to study, many scientists have chosen to focus their attention on some of the more exciting planets. A big part of Uranus’s secrecy lies in its atmosphere.

The lower layers of the atmosphere are so dense and thick that we can’t really get a good idea of what’s going on beneath—at least, not until our observational tools develop further.