SATURN, THE LORD OF THE RINGS

Saturn photographed by Hubble Space Telescope. On the surface of the planet, near the equator, you can see a cyclone with white clouds of ammonia ice crystals.   (JPEG, 160 K)  (NASA-STScI)

Saturn in a photograph of Voyager 2 in 1981. Its atmospheric circulation is organized in parallel bands, as for Jupiter. In fact, as on the other gaseous giants, the winds are prevalently directed along lines of constant latitude. The rings are classified with letters of the alphabet on the basis of their discovery. The most evident separation, between the rings A and B, is called "Cassini's division", from the name of the scientist who discovered it.  (JPEG, 128 K)  (NASA-JPL)

The rings of Saturn in an image with intensified colours that indicate its different chemical structure. This swarm of ice particles and rocks, from the size of a few centimetres to a few meters, is at such a distance from the planet that its tidal forces would destroy any larger body that originated from the aggregation of the fragments.  (JPEG, 67 K)  (NASA-JPL)

Mimas is the most internal of Saturn's major satellites, here in a picture of Voyager 1 with a resolution of 8 km. It is a frozen object, heavily craterized, with a diameter of 400 km approximately. The large impact crater, (called Herschel in honour of the discoverer of the satellite), has a diameter that measures 120 km and is 6 km deep. (JPEG, 37 K)  (NASA-JPL)

Among the satellites of Saturn, Enceladus is the most interesting to the geologists. Although it is very similar to Mimas as far as the dimensions are concerned (500 km the diameter), its surface, formed by ice, is geologically dominated by internal activities rather than by impact craters. This image, which has a resolution of 2 km, shows large regions of the surface free from craters, as a demonstration that relatively recent events have modelled the surface, presumably due to volcanic activities.  (JPEG, 78 K)  (NASA-JPL)

Tethys, approximately 1,000 km the diameter, is two times larger than Mimas and Enceladus. This frozen satellite is heavily craterized, but shows the signs of a geological activity in the past. The most evident is the large valley (Ithaca Chasma) that stretches for 270 degrees approximately around its surface, partially visible in this photograph of Voyager 2, with a resolution of 5 km.  (JPEG, 68 K)  (NASA-JPL)

The double nature of Iapetus, this bizarre satellite of Saturn, is clearly shown in this Voyager 1 picture. The most luminous, frozen region, has an appearance analogous to that of the other satellites of Saturn. The side that faces the planet is formed by a large dark area, the nature of which is not yet known. The answer to this and many other questions should come from the next ESA/NASA mission to the system of Saturn, called Cassini/Huygens.  (JPEG, 39 K)  (NASA-JPL)

Titan, the largest satellite of Saturn, is larger than the planet Mercury, but is wrapped in a thick atmosphere and in many layers of opaque clouds. The surface of the satellite cannot be seen through the clouds, but the atmosphere is particularly interesting because its composition in Hydrogen, Nitrogen, Methane and other hydrocarbons is very similar to that supposed to be the primitive atmosphere of the Earth before the appearance of life.  (JPEG, 47 K)  (NASA-JPL)

Computerized image of the Cassini probe during the manoeuvre by which it was placed on its orbit around Saturn. The manoeuvre, which will take approximately 90 minutes, will allow the probe to remain on its orbit for 5 months.  (JPEG, 54 K)  (NASA-JPL)

Saturn appears beyond the surface of Titan in this artistic image that depicts the Cassini-Huygens mission. The Cassini spacecraft flies in the distance with its large antenna pointed towards the Huygens ESA probe which is entering the atmosphere of Titan to reveal its secrets. It is planned that Huygens will get through the atmosphere in 2 hours approximately and that it will continue to send data for thirty minutes, if it survives the landing. The surface of Titan could have lakes of liquid hydrocarbons, over a thin crust of methane and ammonia. The orange colour depends on the presence of hydrocarbons in the atmosphere and on the surface of Titan.  (JPEG, 396 K)  (NASA-JPL)

The Cassini spacecraft will be equipped with a large antenna that, besides maintaining communications with the Earth, will have the task to carry out radar investigations on Saturn, the rings and the surface of the satellites. The drawing shows the capability of Cassini to go through the atmosphere of Titan, and map its surface.  (JPEG, 98 K)  (ASI)

A view of Saturn from Voyager 1. You can also see the satellites Tethys and Dione. On the surface of Saturn you can notice the shadows of the satellites and of the rings. (JPEG, 39 K)  (NASA-JPL)

Sunset on the rings. This image, of November 1995, is a mosaic of 8 expositions, taken by the Space Telescope. The view is unusual because the Earth was slightly above the plane of the rings, and the Sun below it.  (JPEG, 23 K)  (NASA-STScI)

The CASSINI spacecraft, which will be launched towards Saturn together with the Huygens probe, will be one of the largest interplanetary vehicles ever to be launched, as high as a two storey building and as heavy as 6 tons.
 

CASSINI-HUYGENS is a programme of international collaboration of NASA, ESA and ASI. The mission is scheduled to start in October 1997, and will reach Saturn in 2004. The mission will last 11 years. The spacecraft CASSINI (from the name of the French-Italian astronomer Jean Dominique Cassini who studied Saturn in the 17th century), will travel for seven years, rotating twice near Venus and once near the Earth and Jupiter, and will eventually reach Saturn and release the Huygens probe (from the name of the Dutch scientist who discovered Titan in the 17th century) to explore the atmosphere and the surface of Titan. The Space Agencies, scientific organizations and industries of 17 countries will participate to this mission. The major Italian contribution is represented by the complex high gain four band antenna, which will be the "voice" and the "ears" of the CASSINI spacecraft, sending data and receiving orders from the Earth for the entire length of the mission.

The HUYGENS probe.  The descent of the Huygens probe towards Titan will start in November 2004. HASI (Huygens Atmospheric Structure Instrument) will be the first experiment to operate during the entering of the atmosphere, and will provide information on density, temperature, pressure and electric properties. It will also send data on the Surface of Titan, both liquid and solid. The organization of the activities of development and realization of the experiment, is the responsibility of CISAS, Centro interdipartimentale di Studi e Attivita' Spaziali (Interdepartmental Centre for space studies and activities) "G. Colombo" of the University of Padua.  (JPEG, 378 K)

 
 

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