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Assignment 15-1

Comparative Planetology:

Uranus and Neptune are considered sister planets. We call them sisters because they are so similar. Pluto, however, is different from every other planet in the Solar System. Pluto is actually more like a comet than a planet. In fact, Pluto was recently reclassified as a dwart planet, but we’ll talk more about that later.

Uranus and Neptune:

We began our journey through the Solar System talking about the small dense inner planets. We then explored the very large middle two planets Jupiter and Saturn. Uranus and Neptune are in between. They are not gigantic, but they are not small either. Uranus takes up 67 times as much space as the Earth while Neptune takes up 57 times as much space.

Planetary ingredients:

In addition to being so similar in size, these two worlds are also made up of the same ingredients. They have a hard rock core about the size of the Earth. Around that rock core is a huge liquid water ocean thousands of miles deep. Think about that, these two worlds actually have liquid water oceans. On top of the water oceans sits another ocean of liquid metallic hydrogen.

Both Uranus and Neptune have an atmosphere of mostly hydrogen, helium and methane. The weather of these atmospheres is quite active. One very large storm on Neptune is similar to Jupiter’s great red spot. This storm is called The Great Dark Spot.


After talking about the gigantic water oceans of these two worlds, we need to talk about life. Wherever we find liquid water, we believe there is a possibility we might also find life. This may or may not be true for Uranus and Neptune.

The first problem that life would encounter is that at the enormous depths of this ocean there would be absolutely no sunlight whatsoever. Life on the Earth requires either sunlight or heat from volcanoes to absorb energy.

The second problem that would make it difficult for there to be any life on Uranus or Neptune is the titanic pressure that would squeeze any plants or animals very tightly. It is impossible for humans to visit the depths of our own oceans, even in submarines, because of the pressure. The pressure of these planets’ oceans would be millions of times more powerful. All of this does not mean there is not life on Uranus or Neptune. It just means that it is unlikely.


Saturn’s beautiful ring system is not alone in the Solar System. Along with Jupiter, Uranus and Neptune both have a system of rings.


There are not many differences between these two worlds, but there are some. The major difference is the way these planets rotate. Every planet in the Solar System rotates counter clockwise except for Uranus. Uranus rotates, or spins, on its side.

It is believed that billions of years ago a very large object, possibly as large as the Earth, smashed into the side of Uranus. This collision was so powerful that it completely changed the rotation of Uranus. Another new idea about why Uranus spins on its side is that long ago when our Solar System was still new, perhaps a large moon that orbited Uranus was pulled away by another very large planet. It is thought that maybe the force of this large moon being pulled away caused Uranus’ axis to tilt, leaving Uranus to rotate on its side.


Assignment # 1:

Name three similarities between Uranus and Neptune.


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Both Have Many Moons
Identical Atmosphere
Both Have Rings
Similar Size