NASA Cassini Mission to Saturn set for fiery Grand Finale
By Amanda Jermyn



Twenty years after it was first launched, the Cassini mission to Saturn will come to a spectacular end this September in what is being dubbed the ďCassini Grand Finale.Ē

A joint venture of NASA, the European Space Agency and the Italian Space Agency, Cassini was launched in October 1997, and began orbiting Saturn in July 2004. While three earlier space probes have flown by Saturn, Cassini was the first to enter its orbit. Its lander, Huygens, touched down on Saturnís moon Titan in January 2005, making history with the first ever landing in the outer Solar System.

Cassini has been a star performer, returning remarkable data and photos of the ringed planet and its moons. Input from Cassini and the Huygens lander shows Saturnís moon Titan to have some Earth-like processes, such as clouds, rain, sand dunes, volcanoes, and rivers and lakes of methane and ethane. The nitrogen, ethane and methane in Titanís atmosphere hold the potential to assemble themselves into amino acids that form the basis of what we call life. In addition, the data from Cassini suggests that beneath Titanís surface lies a liquid water ocean, and where there is water there is also the possibility of life.

Saturnís moon Enceladus lies within the densest part of the planetís E ring, a wide band of dust and ice particles that forms the outermost ring orbiting the planet. On Enceladus Cassini has discovered volcanoes spewing large jets of ice particles that feed the E ring. The probe has also revealed that close beneath this moonís icy surface lies an ocean of liquid water that might have conditions conducive to life.

Furthermore, the Cassini mission has allowed scientists to study the size, temperature, distribution and composition of Saturnís rings, and to capture the interactions between the rings and the planetís moons. Viewing the rings at the equinox when sunlight strikes the rings edge on has also revealed features of the rings that have never been seen before.

So why end a mission that has produced such spectacular results? After its twenty year journey, Cassini is starting to run low on rocket fuel. Without intervention, this could result in the mission operators losing control of the course of the spacecraft. Cassini data has revealed the potential for life on Titan and Enceladus, and if there were life there it would be important not to contaminate it with life from Earth. So to prevent even the remote possibility of Cassini some day colliding with one of these moons and contaminating it with any hardy Earth microbes that might have survived on the spacecraft, NASA has decided to end the mission by steering Cassini into Saturnís atmosphere.

On April 22nd Cassini will fly over Saturnís rings to begin its final series of orbits between the planet and the inner edge of the rings. In September this year, after 22 of these orbits, the spacecraft will dive into Saturnís upper atmosphere where it will burn up in the Grand Finale, ending its mission to the ringed planet.

During this final phase Cassini will take close up photos of Saturnís rings and clouds. This should improve our knowledge of how much material is in the rings and help us understand their origins. The spacecraftís particle detectors will sample the icy ring particles being channeled into the atmosphere by Saturnís magnetic field.

Cassini will also map the planetís gravity and magnetic fields, detailing how Saturn is arranged on the inside, hopefully providing insights into how fast the interior is rotating.

Though it will be sad to witness Cassiniís demise, we can take pride in the extraordinary wealth of knowledge gained from the mission. Its success provides hope and inspiration for future planetary missions.

Join the Springfield Stars Club on Tuesday, April 25th at 7:00pm at the Springfield Science Museum for a talk by Crystal Mengele on ďThe European Space Agency.Ē Crystal is a histotechnologist and electron microscopist at Baystate Medical Center. She is a former president of the Amherst Area Amateur Astronomy Association and a board member of the Springfield Stars Club. Refreshments will be served, and the public is welcome. The meeting is free of charge for members, with a suggested donation of $2 per non-member.

Also, on Friday, May 5th at 7:30pm, the Stars Club and the Springfield Science Museum will host ďStars over Springfield,Ē an astronomy adventure for the whole family. Stars Club president Alan Rifkin will talk on ďHow to view the upcoming Solar Eclipse.Ē A fee of $3 for adults and $2 for children under 18 will be charged