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Cassini Bids Farewell from Saturn

LAST SIGNAL OF CASSINI PROBE

At 2 pm on September 15, 2017, NASA antennas in Australia received the very last radio signal transmitted from the Cassini probe one hour and 23 minutes earlier from Saturn’s external atmosphere. A few seconds later, the probe disintegrated on account of the powerful aerodynamic forces incurred at 30 km/second. Sapienza Professor Luciano Iess, who participated in the project’s preliminary phases, flew to the United States for this “farewell kiss.”

During the final stages of the mission, which began on April 26, 2017, Cassini passed close to Saturn 22 times, shedding light for the first time on the internal structure of the gaseous giant and revealing the age of his rings. On September 12, Sapienza Researchers presented this revolutionary data to the Cassini Team.

Cassini began its long voyage on October 15, 1997, with a spectacular launch from Cape Canaveral. The mission objective, led by NASA in collaboration with the Italian Space Agency (ASI) and the European Space Agency (ESA), was to explore Saturn, its many moons and spectacular rings. Cassini arrived at its destination on July 1, 2004 and began maneuvers to enter a complex sequence of orbits that would allow it to survey all the planet’s satellites and closely observe its rings. The number of discoveries made thanks to Cassini exceeded all expectations.

Sapienza University contributed to the Cassini Mission by developing two fundamental on-board devices (radar and frequency transducers built by Thales Alenia Space Italy) and producing some of the most important scientific results of the mission.

A first goal was achieved in 2002, when the probe was still travelling between Jupiter and Saturn, by measuring the propagation delay of radio signals caused by solar gravity. To date, this is the most accurate experimental confirmation of Einstein’s Theory of General Relativity.

Then, whilst orbiting Saturn, Cassini revealed the seas and lakes of liquid hydrocarbons on the surface of Titan, the second largest moon in the solar system, analysed the internal structure of the satellite and discovered its rocky nucleus with a 2000 km radius of hydrated silicates. Measurements of the tides on Titan revealed the existence of an ocean of liquid water under the satellite’s ice crust. Bathymetry of the moon's seas revealed depths of up to 170 metres.

Moreover, in 2014, a large amount of liquid water was detected below the frozen crust (-190° C) in the southern Polar region of Encelado, one of Saturn’s moons. The fact that the ocean "rests" on a rock and silicate base makes it an ideal environment for the development of complex chemical reactions necessary for life.

Members of Cassini Scientific Team are coordinated at the Sapienza Department of Mechanical and Aerospace Engineering by Professor Luciano Iess together with Professor Roberto Seu at the Department of Electronic Engineering and Telecommunications. 

"During more than ten years in Saturn’s atmosphere, Cassini has visited all its major moons and allowed a series of extraordinary discoveries," emphasizes Professor Iess, "and the legacy for the international scientific community is immense."