Saturn's satellites: Enceladus, Titan, Dion, Tefii and others - differ in size, shape and structure. Large and icy moons are adjacent to small and stony. One of the most interesting objects in this system is Enceladus. Studies suggest that the sixth-largest satellite of Saturn has a subsurface ocean. Scientists call Enceladus a real candidate for finding life in its simplest forms.
Gas giant
Saturn is the second largest planet in the solar system. In diameter, it is only slightly inferior to the leader in this regard, Jupiter. However, the mass of Saturn is not so great. Its density is less than a similar parameter of water, which is no longer characteristic of any planet in the system.
Saturn, like Jupiter, Uranus and Neptune, belongs to the class of gas giants. It consists of hydrogen, helium, methane, ammonia, water and a small amount of heavy elements. Saturn has the brightest rings in the solar system. They are made of ice and dust. Particles vary in size: the largest and rare ones reach tens of meters, most no more than a few sentiments.
Cassini
In 1997, the Cassini-Huygens apparatus was launched to study Saturn and its moons. He became the first artificial satellite of the gas giant. “Cassini” showed the unknown Saturn to the world: photos of a hexagonal storm, data on new moons, images of the surface of Titan significantly supplemented scientists' knowledge about this gas giant. The apparatus still works and continues to provide researchers with information. A lot of "Cassini" spoke about Enceladus.
Satellites
The gas giant has at least 62 moons. Not all of them got their own names, some due to their small size and other factors are indicated only by numbers. The largest gas giant moon is Titan, followed by Ray. Saturn's satellites Enceladus, Dion, Iapetus, Tethius, Mimas and several others also differ in rather large sizes. However, an impressive part of the moons in diameter do not exceed 100 m.
Of course, among such a cluster there are also unique objects. Titanium, for example, ranks second in size among all the satellites in the solar system (in the first - Ganymede from the "retinue" of Jupiter). However, its main feature is a very dense atmosphere. Recently, astronomers are increasingly sending their telescopes to Saturn’s satellite Enceladus, a brief description of which is given below.
Opening
Enceladus is one of the largest moons of Saturn. It was opened the sixth in a row. In 1789, William Herschel discovered it with his telescope. Perhaps the satellite would have been discovered earlier (its size and high albedo greatly contributed to this), but the reflection of the rings and Saturn itself prevented Enceladus from seeing. William Herschel watched the gas giant at a good time - and this made the discovery possible.
Parameters
Enceladus is the sixth largest satellite of Saturn. Its diameter is 500 km, which is about 25 times less than the same parameter of the Earth. By mass, the satellite is inferior to our planet almost 200 thousand times. The size of Enceladus does not make it any outstanding space object. The satellite is distinguished by other parameters.
Enceladus has a high reflectivity, its albedo is close to one. In the whole system, it is probably the lightest object after the Sun. The reason for the brightness of the star in the high surface temperature, Enceladus is different. It reflects almost all the light that reaches it, because it is covered with ice. The average surface temperature on the satellite is -200 º.
The satellite’s orbit is close enough to the rings of Saturn. It is separated from the gas giant by a distance of 237,378 km. The satellite makes one revolution around the planet in 32.9 hours.
Surface
Initially, scientists were not so interested in Enceladus. However, the Cassini apparatus, which came quite close to the satellite several times, transmitted extremely curious data to Earth.
The surface of Enceladus is not rich in craters. All available traces of meteorites are concentrated in small areas. A feature of the satellite are numerous faults, folds and cracks. The most amazing formations are located in the area of the south pole of the satellite. Parallel tectonic faults were discovered by the Cassini apparatus in 2005. They got the name "tiger stripes" for their resemblance to the figure of a mustachioed predator.
According to scientists, these cracks are a young formation testifying to the satellite’s internal geological activity. Tiger stripes 130 km long are separated by 40 km intervals. The Voyager 2 spacecraft, which flew past Enceladus in 1981, did not notice faults at the south pole. Researchers suggest that the cracks are exactly less than a thousand years old, and, quite possibly, they appeared only ten years ago.
Temperature Anomalies
The orbital station recorded a non-standard temperature distribution on the surface of Enceladus. It turned out that the south pole of the cosmic body heats much more than the equator. The sun is not able to lead to such an anomaly: traditionally the poles are the coldest parts. Scientists involved in the study of Enceladus have come to the conclusion that the cause of heating is an internal source of heat.
It is worth mentioning that the surface temperature in this place is large precisely by the standards of such a remote section of the solar system. Saturn's satellites: Enceladus, Titan, Iapetus and others - cannot boast of hot areas in the usual sense. The temperature in the anomalous zones is only 20-30º higher than average, that is, approximately -180 º.
Astrophysicists suggest that the reason for heating the satellite’s south pole is the ocean below its surface.
Geysers
The subsurface ocean at Enceladus makes itself felt not only by heating the south pole. The liquid that makes it escapes in the form of geysers through the “tiger stripes”. Powerful jets were also seen by the Cassini probe in 2005. The device collected samples of the substance that makes up the flows. His analysis allowed us to make two assumptions. Near the surface, particles escaping from the "tiger stripes" contain a large amount of salts. They indicate the existence of the sea under the surface of Enceladus (and this is the first conclusion of scientists from the data of "Cassini"). At a much higher rate, particles with a lower salt content break out from the cracks. Hence the second conclusion: they form the ring E, on the "territory" of which Saturn’s satellite is actually located.
Subsurface ocean
An impressive fraction of particles escaping is close in composition to seawater. They fly out at relatively low speeds and cannot become material for ring E. Salt particles fall on the surface of Enceladus. The composition of the escaping ice suggests that its source cannot be the satellite’s frozen crust.
Researchers suggest that the salt sea is located at a depth of 50 miles below the surface of Enceladus. It is limited on one side by a solid core and an ice mantle on the other. The water in the interlayer is in a liquid state, despite the low temperature. It does not freeze due to the high salt content, as well as due to the tidal energy created by the gravitational field of Saturn and some other objects.
The amount of evaporating water (approximately 200 kg every second) indicates a huge area of the ocean. Jets of water vapor and ice burst to the surface as a result of the formation of cracks, which lead to a violation of pressure.
Atmosphere
The automatic interplanetary station "Cassini" discovered on Enceladus and the atmosphere. For the first time it was registered by the magnetometer of the apparatus by the effect on the magnetosphere of Saturn. Some time later, the Cassini recorded it directly, observing an eclipse by the satellite of Gamma Orion. Research of the probe revealed the approximate composition of the atmosphere of the ice moon of Saturn. At 65%, it consists of water vapor, molecular hydrogen (about 20%) is in second place in concentration, and carbon dioxide, carbon monoxide and molecular nitrogen are also found.
The source of replenishment of the atmosphere is supposedly geysers, volcanism, or gas emissions.
Is there life on Enceladus?
Detecting water in a liquid state is a kind of pass to the list of potentially inhabited (path only by simple organisms) planets. According to scientists, if the ocean under the surface of Enceladus has existed for a long time, since the inception of the solar system, then the probability of detecting life in it is quite high, provided that water is kept in liquid state for almost all this time. If the ocean periodically freezes, which is quite possible due to the impressive distance to the sun, then the chance of habitability becomes extremely small.
To confirm or deny the assumptions of the researchers now only information coming from the Cassini probe is capable of. His mission is extended to 2017. It is not known how soon other interplanetary stations will be able to go to Saturn and its satellites. The distance from Earth to Enceladus is great, and such projects require careful preparation and impressive funding.
The Cassini probe continues to operate. He was heading to explore the gas giant and Saturn's moons. Enceladus, however, was not on the list of main tasks. Discovered features included him in the list of objects of paramount importance. No one expected to find liquid water in the area of the solar system where Saturn is located. Photos of geysers on Enceladus and a few years after the discovery seem incredible. It is entirely possible that the satellite’s surprises do not end there, and before the completion of the Cassini mission, astrophysicists will still find out a lot of interesting things about this ice moon.