#长文创作激励计划#
In the solar system, Saturn has the largest number of moons. In May last year, scientists confirmed 28 new moons of Saturn.
This brings the number of Saturn's moons to a staggering 117, while Jupiter, another city with a large number of moons, has only 95 moons.
Not all of Saturn's moons were discovered after the progress of human science and technology, and astronomers began to recognize Saturn's moons more than 300 years ago.
Among so many satellites, there is one that is quite special. Due to its peculiar appearance, many people even believe that it is not a satellite, but a hidden spaceship.
So, what's so peculiar about this satellite? When was it discovered?
The "yin and yang face" of the sky more than 300 years ago
Back 353 years ago, in the fall, the astronomer named Cassini was observing Saturn as usual.
One night, he used a telescope to discover a brand new star in the western region of Saturn. Fast forward to the following spring, and Cassini was still observing and searching for the star in the clear night sky.
He had been observing it in the western region of Saturn, and he wanted to see it from the eastern region of Saturn. But Cassini made a mistake, no matter how he observed, after changing areas, he just couldn't see the star.
After a year's wait, he saw the star again on the west side of Saturn, and then in February of the following year, he saw it again in the same airspace.
The star discovered by Cassini is known as Iapetus. Counting from the inside of Saturn, it is in its eighth orbit. And judging by all the moons of Saturn, it is the third largest moon.
For Cassini, what he was most concerned about at the time was why the star was sometimes invisible. This situation bothered Cassini for a long time, until 1705, with the improvement of telescope technology, Cassini finally saw it in the eastern region of Saturn.
It's just that in terms of brightness, Titan seems to have different brightness in different areas. Cassini came to the bold conclusion that the star was characterized by its ability to distinguish between two halves.
Half is bright, half dim, and the bright side is always facing its parent planet, Saturn. Because of this characteristic, when humans observe the Earth, they will always see the bright part of the western region of Saturn.
Because the eastern area was dark, it was not seen when Cassini's telescope was not improved.
Cassini's guess at the time was undoubtedly correct, and more than 300 years later, mankind had more advanced telescopes and could use probes to observe them up close, further clarifying the light and dark characteristics of Iapetus.
Half looks bright, half dark, hence the nickname of the yin and yang face. The question is, why does this satellite show such a strange state?
The meteorite "fanned" half of its face and swollen
If the surface of the stars is regarded as human faces, the faces of most of the planets discovered by mankind so far in the solar system and even in the universe are symmetrical and the color is the same.
But Titan is one such exception, its face looks different shades and colors.
To this day, when scientists observe Titan from Earth, the line between light and dark is clear. In order to make a distinction, Cassini, who first discovered Iapetus, was named after the bleak side, called Cassini District. The bright side is named after Lonsesvalles.
Cassini was alive at a time when telescopes had limited technology, so scientists only discovered this phenomenon, but it is difficult to explain what the reasons behind its formation were.
By the 20th century, scientists believed that the surface of Iapetus was caused by a combination of meteorite impacts and differences in surface temperature.
On the surface of Titan, the dull side is filled with more dark material, so it appears darker. Figuratively speaking, it's like a meteorite fanning Iapetus's face, half of the face is swollen, so it looks darker in color.
At the same time, the impact of meteorites is only one factor in the formation of this difference between light and dark, and there are more critical temperature factors at play in the middle.
Scientists have previously found that the overall mass of Titan is only one-fortieth that of the Moon, and the volume is light and dense, so scientists speculate that most of the interior of Titan should be composed of water ice. The innermost core area of the rock should be small.
In addition, every time Titan autobiography, it is equivalent to 79 days on Earth. Such a long autobiographical period has led to a large difference in temperature between the two regions of Iapetus facing the sun and facing away from the sun.
According to scientists' speculation, the Cassini zone of Iapetus is also the dark side, and the temperature in this area is much warmer than that of the bright area because the dark part is more likely to absorb heat.
Very high temperatures mean that in dark areas, the ice is more likely to melt, while in other bright areas, it is re-condensed.
This distinction will lead to an increasing difference between light and dark. Scientists speculate that the dark material in the dark area is not only filled with meteorite impact components, but also coarse debris formed after the melting of the ice on the surface under the temperature difference.
Over time, dark areas look darker and darker. According to scientists' previous speculations, the ice in the dark area may have melted for 20 meters over a period of up to 10 million years.
And in the part of the bright area, the disappearing ice may be only 10 meters. The significant difference between the two also makes the distinction between light and dark more and more obvious.
In the solar system, whether it is a planet or a small moon, only the surface of Iapetus has this clear difference.
In addition to this, Titan is different from other satellites, and there are other more special aspects of its surface.
Welds, belts, ridges
For a long time, scientists could only observe Titan through telescopes, and it was not until the probe approached the region where Saturn is located that scientists could see Titan up close.
In 2004, the Cassini probe took a close-up picture of the surface of Iapetus. When the information was transmitted back to Earth, scientists were surprised to find that there was a clearly raised area on the surface of Titan.
This protrusion is narrow, averaging only about 20 kilometers, but it is very long, spanning 1,300 kilometers. As for its height, it averages 13 km, with some of the highest areas reaching 20 km.
Such a peculiar landform looks, from a distance, like a belt wrapped around Iapetus. Within the astronomical community, astronomers refer to it as the equatorial ridge, or equatorial ridge.
What's even more interesting is that this peculiar bulge does not completely surround Iapetus, but mostly only appears in the middle of the dark sphere.
After further analysis, scientists found that the topography of this narrow area is very complex, ranging from towering peaks to cliffs hundreds of kilometers long.
In addition to this, there are parallel ridges in some areas. The combination of these different terrain units makes this belt look rather eerie.
In the bright part of Titan's surface, there is no such ridge. Within this area are a number of separate peaks that can reach heights of more than 10 km.
Scientists have also found that there are many places on the dark side of the equatorial ridge that have been violently impacted. This shows that the formation of this landform feature has been a long time.
So, what are the factors that cause this peculiar surface feature?
There are currently three assumptions
Scientists have put forward various speculations over the years around this belt on Titan, and there are currently three mainstream speculations.
The first guess has to do with the rapid rotation of Iapetus in the early days.
Scientists who put forward this hypothesis believe that the equatorial ridge as seen today is a remnant of the early years of Titan formation.
Specifically, in the early years when Iapetus was first formed, the speed of autobiography was quite fast, with scientists calculating the time at 17 hours.
At such an autobiographical frequency, the protruding parts also solidify quickly, and eventually this feature remains in the equatorial region.
The second hypothesis has to do with the structural composition of Titan. Some scientists believe that because Titan is a water-ice structure, there is ice gushing out of the underground area, and then it eventually condenses together, forming a surface characteristic.
This speculation does not explain why the ridge part only exists in the dark area, and why the bright part does not.
The final guess is that scientists believe that the ridge comes from the outside. In the early days of Titan's formation, there was a ring system around it.
This ring system orbits Iapetus, and later partially collapsed, eventually forming an equatorial ridge in parts of Iapetus.
At present, all three of these speculations have their plausible side, but they do not explain why such surface features are only present in certain areas.
Because of this, the popular explanation is relatively simple, and some people believe that the equatorial ridge is not a natural product, but a trace of intelligent life.
The whole of Titan is not a satellite, but a giant flying machine.
Will it be a spaceship
Scientific speculation needs to be rigorous, and popular speculation can be wild. Some people think that the equatorial ridge on Iapetus is like a welded part.
If you think of Iapetus as a giant flying machine, the area of the equatorial ridge is likely to be the connection area of the spacecraft.
In addition to this, Iapetus is light overall, even lighter than the Moon. In science fiction and conjecture, the moon is a vehicle made by aliens, and the lighter size of Titan, coupled with its peculiar appearance, seems to be more in line with the characteristics of the vehicle.
Since it is speculation, you can casually think that if Iapetus is really a flying machine, then the aliens who made it are really rough in technology.
If you can build a vehicle the size of a satellite, why is it so rough on the outside? At the very least, it should be built like another satellite.
From this point of view, it does not seem to indicate that it was built by extraterrestrial life.
epilogue
As it stands, although scientists still don't know much about Iapetus, it's actually a satellite, and the only difference is that it looks rougher on the surface.
In fact, the surface differences of moons or planets are not too strange in the universe. With the further development of human technology, there may be more strange celestial objects to be seen in the future.
Resources:
"117 pieces! Saturn becomes the "king of moons" of the solar system" Science and Technology Daily May 12, 2023
"Titan: Satellites with Strange Surfaces" NASA Chinese Network February 26, 2023
"Iapetus looks weird, some people say it looks like a giant hollow starship, what evidence is there? Popular Science China, April 18, 2021