Cassini Spacecraft and the Huygens Probe

The planet Saturn, its icy rings, the enigmatic moon Titan, other moons and the huge magnetic bubble that surrounds most of them are the prime scientific targets of the international Cassini mission

The mission also entails the first descent of a probe to a moon of another planet, sending
the Huygens probe to the surface of Saturn’s moon Titan — by far the most distant landing ever
attempted on another object in the solar system.

Cassini, in development since October 1989, is a cooperative endeavor of NASA, the European Space Agency (ESA) and the Italian Space Agency, or Agenzia Spaziale Italiana (ASI). The mission will send a sophisticated robotic spacecraft equipped with 12 scientific experiments to orbit Saturn for a four-year period and to study the Saturnian system in detail. The ESA-built Huygens probe that will parachute into Titan’s thick atmosphere carries another six scientific instrument packages. "Saturn, with its rings, 18 known moons and its magnetic environment, is a lot like a solar system in miniature form," said Dr. Wesley T. Huntress, NASA's associate administrator for space science. "It represents an unsurpassed laboratory where we can look for answers to many fundamental questions about the physics, chemistry and evolution of the planets and the conditions that give rise to life.

On November 6, 2004, Cassini will release the disc-shaped Huygens probe toward Titan. After a three-week ballistic freefall toward Titan, the 2.7-meter-diameter (8.9-foot), battery powered Huygens will enter Titan's atmosphere, deploy its parachutes and begin its scientific observations. Data gathered during Huygens' 2-1/2-hour descent through Titan's dense atmosphere will be radioed to the Cassini spacecraft and relayed to Earth. Instruments on the descent probe will measure the chemistry, temperature, pressure, density and energy balance in the atmosphere. As the probe breaks through the cloud deck, a camera will capture panoramic pictures of Titan. Titan's surface properties will be measured, and more than 500 images of the clouds and surface will be returned. In the final moments of descent, a spotlight will illuminate the surface for spectroscopic measurements of its composition. If the probe survives landing — which should occur at a fairly low speed of about 25 kilometers per hour — it may return data from Titan's surface, where the atmospheric pressure is 1.6 times that of Earth's and the temperature is -179 C. The exact conditions it will encounter are unknown; the probe could touch down on solid ground, rock-hard ice, or even splash down in a lake of ethane and methane. One instrument onboard will discern whether Huygens is bobbing in liquid, and other instruments onboard could measure the chemical composition of that liquid.

Three months before Saturn arrival, the Cassini spacecraft has observed two storms in the act of merging into one larger storm. This is only the second time this phenomenon has been observed on the ringed planet.

"On Earth, storms last for a week or so and usually fade away when they enter the mature phase and can no longer extract energy from their surroundings. On Saturn and the other giant planets, storms last for months, years, or even centuries, and instead of simply fading away, many storms on the giant planets end their lives by merging. How they form, however, is still uncertain,"

 (NASA PRESS RELEASE  OCTOBER 1997)

What is Cassini seeing?

Saturn's C and B Rings From the Inside Out
 

Moon under Saturn

NASA JPL PICTURES

Titan's surface revealed

The colour image shows false-colour to highlight the diffezronces in Titan's surface. The yellow areas correspond to the hydrocarbon-rich regions, while the green areas are the icier regions. Here, the methane cloud appears white, as it is bright in all three colours.

NASA JPL PICTURES

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