Uranus and Neptune are not the same color.
They are not exactly the same. The deep blue shade of Neptune is very similar to the shade of Uranus. I have seen both of them through a telescope and Neptune is blue and Uranus is green.
They're both very similar. They are both made of the same materials and have the same mass. Their colors are similar due to the presence of methane which absorbs red light from the Sun and reflects the blue light back to space.
They look different. Huge dark spots and white clouds of frozen ammonia can be seen in Neptune. It's just kind of blank. There is a large contrast between the planets.
Astronomers have developed a single atmospheric model of the two worlds that shows what they should look like, and it replicates observations very well.
There is a big difference between them. If Hendrix fans will forgive me, there is a haze all up in Uranus.
We have a good idea of the types of materials that make up both planets. Even though the atmosphere is thousands of kilometers deep, we have complicated physics that explains how these behave in an atmosphere. Predicting what would be seen at specific wavelength is something many of these models are afraid of.
Scientists have developed a model of what such an atmosphere would look like across a broad range of wavelength. They can modify the models to match the observations by using the data from the two ice giants taken with the telescopes.
They discovered that there are three layers of aerosols in the upper atmosphere of both planets. The bottom layer of the atmosphere is made up of suspended hydrogen sulfide and a mix of chemicals produced in the upper atmosphere when it reacts with the sun's rays. The middle layer contains a photochemical haze, but is thin and mixed with methane ice, and at a height where atmospheric pressure is twice as high as sea level. This is where the hazy aerosols are made and it is similar to the middle one.
The haze particles in the upper layer help methane ice condense. The crystals grow quickly and fall to deeper levels. The haze particles are deposited into the deepest layer.
There is a difference in the winds of the two planets. The strongest persistent winds of any planet are blowing at speeds in excess of 1,500 kilometers per hour. The methane is mixed efficiently into the middle haze layer. The atmosphere is made clearer by the snow falling.
The reason they look different is explained. The haze layer is gone due to Neptune's atmosphere being active and very windy. The haze layer above it is thick because of the stolid atmosphere. The features below are blocked and the planet is washed out.
The differences in color are also explained by this. It is nice to see that it agrees with the observations. The haze particles falling deeper into Neptune's atmosphere may explain the large dark clouds seen on Neptune.
For Neptune, they had to add a fourth layer higher up of methane ice particles in order to match what is seen in the long wavelength in theIR. All of this is based on modeling, adjusting parameters in the equations processed by computers, like what molecule absorbs what wavelength at what pressures, the thickness of the layers, and more, and this can be a little ad hoc sometimes. You can twist the dial until you get an answer that matches observations, but that doesn't mean it's the right configuration.
Predicting what else should be seen can be done in this case.
With NASA talking about sending new space missions to the giant keepers of the outer solar system, this kind of science can be used to help design the missions. We don't just send these probes to gather information, we equip them with the instruments that can best accomplish their goals as well as take a more general census of the target worlds.
It will take a long time before that happens. We will continue to watch these planets as our telescopes and cameras get better. Our models show how they act.
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