Cassini Meets The Lord of the Rings


NASA is deliberately crashing its $3.9-billion spacecraft in a fiery “Grand Finale” on Saturn. Why? (NASA)

Revisit Cassini’s legacy with our study guides on two of its discoveries.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.


Discussion Ideas


Illustration by NASA/Jet Propulsion Laboratory-Caltech
  • The world is watching as NASA prepares to crash its Cassini spacecraft into the gas giant Saturn. What is Cassini?
    • Cassini is a sophisticated robotic spacecraft orbiting Saturn and studying the Saturnian system in detail.
      • Cassini is a joint endeavor of NASA, the European Space Agency (ESA) and Agenzia Spaziale Italiana (ASI), the Italian space agency. Cassini originally carried a probe called Huygens, which parachuted to the surface of Saturn’s largest moon, Titan, in January 2005.
      • Cassini has 12 science instruments grouped to study three aspects of the Saturnian system.
        • Optical Remote Sensing: The Composite Infrared Spectrometer (CIRS), Imaging Science Subsystem (ISS), Ultraviolet Imaging Spectrograph (UVIS) and Visible and Infrared Mapping Spectrometer (VIMS) study the Saturnian system using the electromagnetic spectrum.
        • Fields, Particles, and Waves: The Cassini Plasma Spectrometer (CAPS), Cosmic Dust Analyzer (CDA), Ion and Neutral Mass Spectrometer (INMS), Magnetometer (MAG), Magnetospheric Imaging Instrument (MIMI), and Radio and Plasma Wave Science (RPWS) study the dust, plasma, and magnetic fields around Saturn.
        • Microwave Remote Sensing: Radar and the Radio Science Subsystem (RSS) map atmospheres, determine the mass of moons, collect data on ring particle size, and unveil the surface of Titan.
      • Make a model of Cassini with a 3D printer, paper-and-scissors … or dessert!


NASA/Jet Propulsion Laboratory-Caltech


  • Why is NASA crashing Cassini?
    • Vox sums it up nicely: “The space agency really has no other choice. Cassini is nearly out of fuel, and has already been stretched years beyond its intended mission duration. What’s more, keeping it going risks potentially contaminating one of Saturn’s moons … with microbes from Earth.”
      • We don’t want to pollute the solar system!


  • Could terrestrial microbes really pollute moons in the outer solar system?
    • Yes. “Based upon exposure experiments on the Space Station, it is known that some microbes and microbial spores from Earth are able to survive many years in the space environment– even with no air or water, and minimal protection from radiation. Therefore, NASA has chosen to dispose of the spacecraft in Saturn’s atmosphere in order to avoid the possibility that viable microbes from Cassini could potentially contaminate Saturn’s moons at some time in the future.”


Illustration by NASA/JPL-Caltech
  • OK, we have to save the Saturnian system from earthly pollution. What is the “Grand Finale”?
    • It’s awesome, is what it is. We love objects discovering the escape velocity of gas giants.
    • In April 2017, Cassini was placed on an impact course that unfolded over five months of daring dives—a series of 22 orbits that each pass between the planet and its rings. Called the Grand Finale, this final phase of the mission has brought unparalleled observations of the planet and its rings from closer than ever before. On September 15 [Friday], the spacecraft will make its final approach to the giant planet Saturn. But this encounter will be like no other. This time, Cassini will dive into the planet’s atmosphere, sending science data for as long as its small thrusters can keep the spacecraft’s antenna pointed at Earth. Soon after, Cassini will burn up and disintegrate like a meteor.”


  • Why a plunge instead of another method of disposal, such as sending Cassini somewhere else in the solar system, attempting a landing on one of the moons, or crashing into the rings?
    • For science! “The Grand Finale of close dives past the outer and inner edges of the rings, and ultra-close brushes with the planet and its small, inner moons, offered such enormous scientific value that this scenario was chosen for the mission’s conclusion.”


  • If Cassini’s death plunge takes it into Saturn, won’t it pollute the Saturnian atmosphere the way it might pollute the moons?


  • What are the final data scientists are hoping to glean from Cassini as it makes its fiery plunge?
    • The spacecraft will make detailed maps of Saturn’s gravity and magnetic fields, revealing how the planet is arranged internally, and possibly helping to solve the irksome mystery of just how fast Saturn is rotating.
    • The final dives will vastly improve our knowledge of how much material is in the rings, bringing us closer to understanding their origins.
    • Cassini’s particle detectors will sample icy ring particles being funneled into the atmosphere by Saturn’s magnetic field.
    • Its cameras will take amazing, ultra-close images of Saturn’s rings and clouds.
    • Stay tuned!


One of our favorite (of many!) images from Cassini is that bright blue dot in this gorgeous image—that dot is you, me, and everyone else on the planet, from a distance of 1.44 billion kilometers (898 million miles).
Photograph by NASA/JPL-Caltech/Space Science Institute



NASA: Cassini: The Grand Finale Toolkit

Nat Geo: Our Favorite Cassini Discoveries

NASA: Cassini Models and DIY

NASA: Cassini STEM lessons and activities


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