How do we weigh Saturn's aura? Can be formed in the dinosaur era – scientific exploration – cnBeta.COM



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Saturn's aura is the most visible feature of this gas giant planet, but when did it begin to form? According to a new study, the age of Saturn's aura may be similar to dinosaurs, and maybe even slower than the dinosaur era.The age of Saturn's aura has become controversial in the academic world. Some researchers believe that Saturn's aura formed when Saturn was first born about 4.5 billion years ago, because the solar system was filled with small pieces of ice.

But some researchers disagree with that, they suspect that Saturn's aura is younger, perhaps after Saturn's gravity has tore off a recently passing comet or its own frozen satellite.

To solve this case, there is a workable idea, namely weighing Saturn's aura, and saying how much material forms the Saturn's aura which is added together. We already know that the substances that make up the aura of Saturn are brightly colored solid water ice, but over time, these clear water ice particles will gradually suffer "space weathering" and pollute the dark black space dust, thus gradually disappearing. Gloss, become dim. And if we can find out how many substances form Saturn's aura, and then see how much the material becomes dim, combined with the universal blackening speed model, we cannot roughly estimate the age of Saturn's aura. Is that

But the biggest challenge of this method is: How do we weigh the aura?

The latest research work is based on data from the Saturn Cassini-Huygens satellite which was jointly carried out by the United States and Europe. Between 2004 and 2017, this detector orbited Saturn for 13 full years and was the first special Saturn detector launched by humans.

Give Saturn aura "weighing"

That's right, this is the biggest problem with this approach. Prior to this, the Cassini spacecraft, which operated on Saturn, had confirmed that only about 1% of Saturn's halo material had been "contaminated." Now, a team led by Luciano Iess, a member of the Cassini spacecraft project team and a professor at the University of Rome in Italy, has skillfully measured the quality of Saturn's aura, and their related research has been published in January. On the 17th, published in the American journal Science, Ace himself was the first author of this paper.

Let's see, how do they do it?

The basis of the Ace team's work is data from Saturn's "Cassini-Huygens" investigation which was jointly carried out by the United States and Europe. Between 2004 and 2017, the detector orbited Saturn for 13 full years and was the first special Saturn detector launched by humans. In September 2017, because of running out of fuel, under the guidance of the land, the Cassini spacecraft rushed into Saturn's atmosphere in a "suicide-like" position to break and burn, ending this mission. At that time, NASA called this achievement "Grand Finale."

But before ending its mission, the Cassini Detector made the last and irreplaceable contribution to science – it flowed to Saturn and its deepest aura 22 times under the guidance of careful land. The narrow gap has been used to detect the outer edge of Saturn's upper atmosphere and the inner area of ​​the halo at unprecedented distances.

But there are other important things that cannot be ignored from this area: simply, the orbit of the Cassini spacecraft is outside the aura of Saturn, and Saturn's gravitational field that he feels is actually the quality of Saturn and its aura. Produced together. But when Cassini crosses between the two, the situation changes, and the gravitational field produced by Saturn and the aura begins to "attract" each other. Through this "pull", researchers can find out Saturn and its aura. The quality of both separately, of course, has completed the "weighing" of Saturn's aura!

During six flights of Cassini spacecraft through the area between Saturn-Halo, scientists analyzed radio communication signals between the Cassini and Earth spacecraft, about 2,600 kilometers from the peak of Saturn's clouds. That is between 3900 km. Because of the relative motion between the spacecraft and the Earth, radio signals will show the Doppler effect. It seems like you see an ambulance far from the road and then dart past you: You will see that when the ambulance approaches you, the sirens become more and more. Sharp, and when the car moves away from you, the siren gets lower. This is because when you and the ambulance are close to each other, the wavelength of the sound wave is compressed and the sound becomes sharp, on the contrary, the wavelength of the sound wave is pulled up and the sound becomes low. In the same way, radio waves will also show this Doppler effect.

But this effect is very weak, you need very high measurement accuracy. As Ace told the media: "I was shocked by myself. We were able to measure the speed of a spacecraft far exceeding 1.3 billion kilometers, with a millimeter error."

Previously, several probes had conducted similar studies, but the accuracy was much lower. For example, in the 1970s, NASA's "wanderer" detector measured that Saturn's halo quality was around 2.8 billion tons, and the latest estimates based on Cassini spacecraft data were around 154 billion tons. In contrast, the largest mass of asteroids, Ceres (now upgraded to dwarf planets), is around 93.9 billion tons.

In short, according to this data, combined with the velocity model of darkening pure water ice, the research team concluded that Saturn's aura roughly formed between 10 million and 100 million years ago, and translated into more popular languages: Saturn's aura is roughly formed in the Era dinosaurs, even later – know that the dinosaur era ended at the end of the Cretaceous period around 65 million years ago.

In September 2017, because of running out of fuel, under the guidance of the land, the Cassini spacecraft rushed into Saturn's atmosphere in a "suicide-like" position to break and burn, ending this mission. At that time, NASA called this achievement the "Grand Finale".

More about the discovery of Saturn

In addition, the authors also mention more in papers, including Saturn's internal structure which is estimated based on high-precision gravitational field data from the final stage of Cassini. For example, a high-speed jet near the Saturn equator – we already know that its wind speed reaches 1,500 kilometers per hour, compared to the maximum wind speed near the center of the 12-level hurricane on Earth, which is about 126 km / hour. The research team later found that the flow of air descended from the surface of Saturn's atmosphere, at least more than 9,000 kilometers inside Saturn. This large airflow rotates rapidly around Saturn, which is about 4% faster than the bottom layer.

Linda Spilker, a Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL), commented: "An important reform of the theoretical model of Saturn's internal structure during the discovery of internal circulation in Saturn. The question is, what strength causes this external rapid rotation layer to penetrate into depth so big? And what does this mean for the formation of Saturn's internal structure? "

In addition, the research team also mentioned in the paper that the latest data projections show that the core quality of Saturn's rocks is around 15 to 18 times the mass of the Earth. This is roughly the same as the previous estimate. (morning breeze)

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