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Cassini Orbiter

Phase: Operating

Launch Date: October 15, 1997

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Program(s):Outer Planets Flagship

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In the first video showing the auroras above the northern latitudes of Saturn, Cassini has spotted the tallest known “northern lights” in the solar system, flickering in shape and brightness high above the ringed planet.

Cassini_SaturnSaturn As You’ve Never Seen it The cover picture from National Geographic, December 2006. The Sun is eclipsed (behind) Saturn in this picture. The “dark” side of Saturn is seen here lit by ring shine. The rings are made highly visible by forward scattered sunlight.

Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the Cassini Equinox Mission, in September 2010. Now, the healthy spacecraft is seeking to make exciting new discoveries in a second extended mission called the Cassini Solstice Mission.

The mission’s extension, which goes through September 2017, is named for the Saturnian summer solstice occurring in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. Since Cassini arrived at Saturn just after the planet's northern winter solstice, the extension will allow for the first study of a complete seasonal period.

The Cassini/Huygens’ mission is defined in broad terms as a detailed study of Saturn, its rings, icy satellites, magnetosphere, and Titan. A suite of instruments is pursuing answers to detailed questions within each of these areas. The Cassini orbiter has 12 instruments, while the Huygens probe carried six more. The science returned by these instruments represents the efforts of 260 scientists from the United States, and 17 European nations, as well as hundreds of engineers, navigators, and ground support personnel.

NASA's Cassini spacecraft tasted and sampled a surprising organic brew erupting in geyser-like fashion from Saturn's moon Enceladus during a close flyby on March 12, 2008. The Ion and Neutral Mass Spectrometer saw a much higher density of volatile gases, water vapor, carbon dioxide and carbon monoxide, as well as organic materials, some 20 times denser than expected. "Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life," said Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We have quite a recipe for life on our hands, but we have yet to find the final ingredient, liquid water, but Enceladus is only whetting our appetites for more."

Cassini_titan_surfaceThe Surface of Titan As seen for the first time ever by human eyes, through the Huygens probe camera. The view is of “sand” and “rocks”. The sand is sand is composed of hydrocarbon aerosol particulates that have settled out of the atmosphere and the rocks are made of water ice. The temperature of Titan’s surface is about 100 deg. K or -280 deg F.

The rings of Saturn are unique in the solar system in their extent and brightness and are the signature feature by which this planet is known. The Saturn system serves as a model for the disc of gas and dust that surrounded the early Sun and from which the planets formed. Dust and gas discs are now well known in distant galaxies where planets may be forming. Being in our neighborhood, as opposed to light years away, the Saturn system presents the opportunity for close-up study of such discs to gain insight into the early stages of planetary formation.

A major goal of Cassini is the detailed study of Titan, a haze shrouded world with a dense atmosphere. Forty four of Cassini’s 76 orbits include Titan flybys and the Huygens probe was designed to study Titan’s atmosphere and surface. That this atmosphere is rich in organic material, and that living organisms as we know them are composed of organic material, is particularly intriguing. Prior to the mission it was believed that Titan might preserve, in deep-freeze, many of the chemical compounds that preceded life on Earth. This is now confirmed by data returned by Cassini and Huygens. In addition Cassini’s cloud-penetrating radar has revealed lakes, rivers, and erosion channels on Titan’s surface. Wind rippled dunes have been observed. Titan is a geologically active world.

Cassini_Enceladus The ice geysers of Enceladus Sunlight illuminates a thin crescent of the 500 km diameter moon. Scattered light illuminates the geysers which extend several hundred km into nearby space.

Among the icy satellites, Enceladus has proven to be the star attraction. Its south polar region is warm and cracks in the surface, dubbed “Tiger Stripes”, are spewing geysers of water hundreds of kilometers into nearby space, where they form the diaphanous E-ring. Liquid water, another necessary ingredient for life, may exist below the surface. Enceladus must have a substantial internal heat source to drive these geysers. Scientists are now trying to understand what this heat source might be and what other secrets the interior of Enceladus might hold.