After Hua Feng came back to his senses, he learned more about the secrets of this wonderful feathered planet.

There is no rain on Enceladus, but there are geysers on its surface, and a lot of water vapor is ejected from them, a process known as a glacial volcano (c).

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i**)。 Opinions differ as to the exact composition of the satellite and the plume of smoke that extends from its surface. Some believe that the moon's fluid surface is covered with a layer of ice, while others believe that it is a cold object made of solid ice and rock.

European and American astronomers recently reported in the journal Science that they judged by analyzing the gravitational field that Saturn's moon Enceladus has a huge "subterranean sea". This is perhaps one of the ideal locations to search for extraterrestrial life.

Enceladus is a "small world" with a diameter of only about 500 kilometers, and its surface is wrapped in dazzling white ice. In 2005, the Cassini probe discovered that Enceladus' south pole was dotted with parallel bands called tiger stripes and ice geysers, leading scientists to speculate that Enceladus may have an "underground sea".

Astronomers used data from three close-up observations of Enceladus by the Cassini probe between 2010 and 2012 to analyze and determine Enceladus' gravitational field. The study found that there is a "striking asymmetry" in Enceladus' gravitational field, in which the gravitational pull of the South Pole is weaker but larger than calculated based on its topography. They believe that it is the liquid water beneath the surface of the Antarctic that "plays a compensatory role", because water is denser than ice and forms a greater gravitational pull than ice.

Further analysis suggests that the "subsurface sea" lies beneath a 30 to 40 km thick surface ice at Enceladus' South Pole, which is about 10 km thick and extends to about 50 degrees south latitude. David Stevenson, a professor at the California Institute of Technology who participated in the study, said: "This means that it is about the same size as or even larger than Lake Superior, the second-largest lake on Earth. ”

The study also showed that the seafloor of Enceladus' "subterranean sea" may be silicate rocks, meaning that the environment is suitable for complex chemical reactions, including those that may have created an environment similar to that of the early Earth.

In addition, scientists believe that Europa, the moon of Jupiter, which is similar to Titan, may also have an "underground sea". Stevenson said studying the two moons will help understand the habitable environment in the solar system. There must be other planets in the solar system that are well-watered.

Enceladus orbits Saturn 238,000 kilometers from its center and 180,000 kilometers from the top of its clouds. Titan is ranked 14th in order of distance from Saturn, and its orbit is located between the dense part of Saturn's E ring and Titan, with an orbital period of 32.9 hours (its displacement can be observed in one night). Its orbit resonates with Titan's orbit at a ratio of 2:1, i.e., every time it completes two revolutions, Titan completes one revolution. This orbital resonance relationship results in a centrifugal rate of 0.0047 in the Enceladus orbit and provides a heating source for its geological activity.

Like most of Saturn's large moons, Enceladus' rotation is synchronized with its revolution, and it always remains on the same side facing Saturn. Unlike the Moon, Enceladus does not oscillate its axis of rotation (while the Moon oscillates by more than 1.5°). However, analysis of Enceladus's shape shows that sometimes it perturbates its orbit due to external forces, such as Titan's orbital resonance effect. This disturbance can also provide an additional source of heating for Enceladus.

The E ring is Saturn's outermost ring, extremely wide (the widest of Saturn's rings), but also extremely thin, consisting of only very fine ice crystals and dust, the ring starts in the orbit of Enceladus and extends to the vicinity of Titan's orbit, and some observers even believe that it has extended to the vicinity of Titan's orbit, so that its width will reach 1 million kilometers.

However, numerous mathematical formulas have shown that such a ring is unstable and can only last for 10,000 to 1 million years, suggesting that the particles that make up the ring must have been replenished from somewhere, and Enceladus' orbit is right in the middle of the ring and in the densest part of the ring. As a result, some theories speculate that Enceladus is the source of the particles that make up the E-ring. Cassini's observations support this view.

Enceladus orbits within Saturn's E rings, and in fact, there are two different mechanisms that complement the particles in the rings. First and foremost, there is the plume ejecta in the south pole region of Enceladus, and although most of the ejecta falls back to the surface of the satellite, some of the material escapes Enceladus' gravitational control and enters the orbit around Saturn, as Enceladus' escape velocity is only 866 km/h.

The second mechanism is that the bombardment of Enceladus by meteors causes dust raised on its surface to enter the ring. This mechanism is not unique to Enceladus, it works on all the moons in the E ring, and from Enceladus, Saturn occupies a viewing angle of nearly 30°, which is more than 60 times larger than the perspective of the Moon as seen from Earth. In addition, because Enceladus's rotation is synchronized with its revolution, Enceladus is always facing Saturn from the same side, so Saturn never moves in the night sky of Enceladus (except for small changes due to orbital anomalies), and Saturn is never visible on the side of Enceladus facing away from Saturn.

Saturn's rings have an observable angle of only 0.019° and look like a thin bright line across Saturn's disk, although its shadow on Saturn's disk is clearly recognizable. Just like the Moon on Earth, Saturn on Enceladus has a regular phase change, with a 16-hour cycle from loss to win. The Sun, meanwhile, occupies only 3.5' of perspective, which is 9 times smaller than the perspective of the Moon as seen from Earth

If an observer were to observe Enceladus, he would be able to observe Enceladus (the largest moon in Enceladus' inner orbit) orbiting in front of Saturn every 72 hours. Enceladus' viewing angle is close to that of the Moon, at a maximum of 26', while Iapetus and Titan are the size of stars, with Enceladus having a maximum viewing angle of just over 1°, which is twice as large as the Moon's, but can only be seen from Enceladus' back to Saturn at its closest proximity.

In March 2008, the U.S. Cassini probe flew near Enceladus and sent back photos showing geyser-like ice chips and water vapor eruptions on Enceladus, suggesting that liquid water may be present on the object. Although the photograph does not capture liquid water, scientists believe that the ice chips and water vapor in the photograph come from a "reservoir" at the shallower surface of Enceladus.

The researchers hypothesized that the surface of the liquid water was covered with thin ice. If there is a crack in the ice, the temperature and pressure of the liquid water will drop dramatically, forming an eruption of water vapor on the one hand, and the rapid condensation of water vapor into ice chips on the other, similar to hot springs on Earth, but at much lower temperatures.

Carolyn Porco, an image analysis expert at the Colorado Space Science Research Institute in the United States, said that if liquid water exists on the planet, where the surface temperature is as low as minus 200 degrees Celsius, there may be a heat source underneath. In addition, researchers from the University of Arizona in the United States have analyzed the spectral data transmitted by Cassini and believe that there may be a small amount of organic matter near the south pole of Enceladus.

Recently, NASA's Cassini probe has made new discoveries, according to the latest news, the Cassini probe has found as many as 101 geyser vents under the Enceladus ice, which means that Saturn's "ice moon" has more ice water components, and there is a special heating mechanism underground to melt the ice.

Scientists have found that there may be a large amount of liquid water below its surface, and in the past seven years, the Cassini probe has begun to scan the south pole of Enceladus through a high-resolution camera system, and scientists have been impressed by its unique geology, which is full of cracks that resemble tabby stripes, and tiny ice particles have been spewed out, all of which have been scanned after scientists have confirmed the location of 101 geysers and mapped the distribution of Enceladus geysers, while NASA researchers have also found that several geysers are surrounded by surface heat sources, which may be related to deeper internal heat sources。

The discovery of Enceladus's geysers dates back to 2005, when scientists speculated that Saturn's tidal forces caused heat sources to appear inside Enceladus and erupt at a thinner surface, resulting in geysers carrying Xiaoice particles. Prior to the study, researchers didn't know what role was dominant in this process, or whether the excess energy inside Enceladus could affect the near surface.

In order to determine the location of the geyser, scientists used the triangulation method used in the geological survey to map the relationship between the thermal radiation source and the geyser of Enceladus, and it can be seen that the eruption of the geyser is also more violent in the area with greater thermal radiation, which indicates that the eruption of the geyser on Enceladus is not a near-surface phenomenon, but is related to deeper heat sources, and a large part of these heat sources come from the tidal forces of Saturn. From this, scientists concluded that between the heat source and the surface ice, a huge subglacial ocean could be formed, which reached the surface through narrow channels.

Based on the Cassini detector's high-resolution camera system, scientists observed periodic geyser eruptions in the Enceladus region, which matched well with Saturn's tidal force model, further proving the relationship between heat sources, tidal forces and geysers in Enceladus.

NASA's Cassini probe sent back images of Enceladus' jet, and the Cassini probe even collected some of the material in the Enceladus jet, which was measured by ultraviolet imaging spectroscopy (UVIS), and scientists obtained data on the amount of gas in the jet. The latest detections have found that the jet stream contains ice particles, water vapor and organic compounds.