Overview of Saturn's moon Enceladus

Enceladus is Saturn's sixth largest satellite. It was discovered by astronomer William Herschel in 1789 when he first used the world's largest telescope at that time, with a diameter of 1.2m.

Before the 1980s (when two Voyager spacecraft passed by Enceladus), little was known about Enceladus except that on the surface of the satellite there was water. Enceladus has a diameter of about 500km, equal to one tenth the size of Titan, Saturn's largest satellite.

It is the celestial body that reflects the strongest light in the Solar System (almost 100%). Voyager 1 found Enceladus's orbit in the thickest area of ​​the dispersion belt E. It is thought that this belt was formed from the material sprayed from Enceladus' South Pole. Voyager 2 shows that the satellite is very small but has a complex topography: from the ancient areas of many craters to newly created young areas. Some areas have new surface layers created about 100 million years ago.

Saturn's moon Enceladus.

The vessel Cassini is currently turning around Saturn has provided us with new data about Enceladus. In 2005, Cassini flew very close to Enceladus, photographed and analyzed surface details as well as the environment on Enceladus. Some of the collected data helped us answer the questions posed after the Voyager's first discovery, some of which caused us to ask new questions.

Specifically, Cassini found that the columns of water containing water sprayed from the south pole of the satellite. With the discovery of heat loss and the existence of smooth surfaces and few craters in the southernmost region, it is confirmed that Enceladus still has geological activities. This can be explained by Enceladus being a gas giant's satellite . Such planets often have a satellite system with complex orbits. Some of these satellites resonate with each other, they are unstable or have certain orbital deflections. So the planet's gravitational pull on these satellites is always changing, causing the surface layers of the satellites to contract in orbit, creating heat.

Enceladus is one of the three celestial bodies (extraterrestrial) with physical eruptions (along with Jupiter's and Triton's Star Io satellites. Gas analysis from these eruptions suggests they catch source from a layer of water below the surface of the satellite Along with the chemicals found in the above eruptions, Enceladus is thought to be a particularly important object for graduate students. The cosmic phenomenon also reinforces the hypothesis that belt E originated on matter on Enceladus that was previously mentioned.

Enceladus's trajectory

Enceladus's trajectory (red in color) looks from the north pole of Saturn.

Enceladus is a large satellite located in the inner group of Saturn satellites. By the distance from the center of Saturn, Enceladus is the 14th satellite. It is located in the densest area of ​​belt E, the outermost belt in Saturn's rings. This belt started from Mimas' orbit and stretched near Rhea's orbit, containing tiny particles of ice and dust.

Enceladus is 238,000km and 180,000km away from Saturn and the surface of Saturn (the surface from Saturn's highest atmosphere). Its trajectory lies in the middle of Mimas and Tethys orbit. It turned around for 32.9 hours, fast enough for the observer from the ground to observe its movement in just one night. Enceladus and Dione created each other in a 2: 1 ratio orbit (Enceladus spins two rounds while Dione spins all around Saturn). Resonance caused Enceladus's orbit to maintain relative flatness (wrong center 0.0047) to create an internal source of heat for its geological activities.

Like Saturn's larger satellites, Enceladus always turns only to face Saturn. Unlike the Moon, Enceladus does not oscillate around the spin axis (at least does not fluctuate more than 1.5 °). Even so, analyzing Enceladus's shape still showed that at some point, Enceladus had forced secondary rotation vibrations 1: 4. This oscillation, along with the orbital resonance along with Dione, adds heat to Enceladus.

The size of the moon Enceladus

Enceladus is one of the smallest satellites with enough mass to have a spherical shape. The average diameter of the satellite is about 505km, equal to 1/7 of the moon. This satellite is so small that it is about the same size as the UK. In comparison, Enceladus can easily fit into states like Arizona or Colorado of the United States. The surface area of ​​the satellite is about 800,000 m², nearly 2 and a half times the area of ​​Vietnam.

The size of Enceladus compared to the United Kingdom.

Enceladus is the sixth largest satellite in size and volume in Saturn's satellites, Titan stars (5,150km), Rhea (1,530km), Iapetus (1,440km), Dione (1,120km) and Tethys (1,050km). ). Mimas is the only spherical satellite smaller than Enceladus among Saturn's satellites (besides the smaller Uranus Miranda satellite Enceladus is spherical).

Enceladus has a slightly flattened elliptic shape, its dimensions calculated from photographs taken from Cassini ISS photography are: 513 (a) × 503 (b) × 497 (c) km.

Inside:

1. (a) corresponds to the distance between the two intersection points of Saturn's center axis - Enceladus center with Enceladus surface.
2. (b) is the distance between two poles on the surface facing the direction of rotation and the surface facing the opposite direction.
3. (c) is the distance between the north and south poles. Thus the satellite rotates around the short axis, while the long axis follows the radial axis.

The surface of Enceladus

A surface photo of Enceladus.

Voyager 2 was the first spacecraft to approach Enceladus' surface and take satellite imagery at a relatively detailed level. From these photos, at least 5 types of terrain on Enceladus' surface have been found, including many craters, new flat plains formed by the terrain of the mountains.

In addition, there are linear cracks and ice racks. Flat plains do not have meteorites formed recently, for several hundred million years. It was then realized that Enceladus certainly had to have geological activities such as the eruption of ice or water or other processes that changed the surface until recently. The new dust-free ice on Enceladus's surface areas makes it reflect very strong light (possibly the strongest in the Solar system) with a geometric reflectivity of 1.38 and a Bond reflection rate of 0 , 99 (99% reflectance of electromagnetic energy). Due to the reflection of most sunlight, the satellite surface temperature is very low (about −198 ° C), probably the lowest in Saturn's satellites.

Interact with Saturn's E belt

Enceladus's trajectory looked from the side, showing its position in the E belt.

Belt E is the outermost belt and is the widest belt in Saturn's rings. It extends from Mimas's orbit near Rhea's orbit. Some observations also suggest that belt E even spreads to Titan's orbit, ie 1,000,000km wide. Although very wide, the material in the belt is very thin, including dust and microscopic tape. Because it is too thin and spread, the belt is very unstable. If there is no alternative supply, belt E will quickly disappear in the range of 10,000 to 1,000,000 years. Enceladus is within the narrowest and most material dense range of the belt, so it was previously assumed that the material escaping from Enceladus formed the belt. This hypothesis has been strengthened by the Cassini ship.