Why Did NASA Kill Cassini?

  • By Drew Gannon
  • Posted 09.20.17
  • NOVA

On September 15, 2017 NASA destroyed Cassini—on purpose. Why kill a multibillion-dollar spacecraft?

Running Time: 02:54


Why Did NASA Kill Cassini?

Published September 15, 2017

Brent Buffington: Why get rid of a two billion dollar asset that's orbiting Saturn? It's still executing amazing science, why get rid of it?“

Onscreen: In 1997 The Cassini-Huygens spacecraft launched from Cape Canaveral and headed to Saturn.

Since then it’s been busy: 2.5 million commands executed, 4.9 billion miles traveled, 453,048 pictures taken and on September 15, 2017 Cassini was destroyed.

On purpose.

But why?

Buffington: The short answer is, we're almost out of fuel. But also before we run out of fuel, we have to adhere to what's called planetary protection.

Onscreen: Planetary protection is the principle of avoiding biological contamination of celestial bodies.

Buffington: This is to make sure that we don't pollute a pristine environment that could harbor life, with our own microbes that could be on our spacecraft.

Onscreen: Cassini found a global ocean under the ice of one of Saturn’s moons, Enceladus.

Some scientists believe Enceladus contains the perfect conditions for life.

Buffington: The last thing we want to do is go back to Enceladus in 50 years and land on the surface and discover life, the biggest discovery in the history of mankind, but only to find out five years later, after more analysis, that it was in fact planted there by us because our dirty spacecraft with Earth microbes impacted Enceladus.

So we want to definitively get rid of the spacecraft, and keep all of these environments that are pristine right now, pristine.

So what are the options?

Onscreen: #1 Crash into an uninhabitable rock.

Buffington: You can hit something. So you can hit an icy satellite that's not a high value target from a habitability point of view, a big icy rock like Rhea or Iapetus or some of these moons

Onscreen: #2 Orbit Saturn indefinitely.

Buffington: You can stay in the Saturn system but go into some highly stable orbit and it stays there for hundreds and hundreds of years.

Onscreen: But the chosen solution is…

#3 Burn up in Saturn’s atmosphere.

Buffington: With one Titan flyby you can jump the entire ring system and put yourself in an orbit that actually impacts Saturn

Onscreen: On the way Cassini executes 22 close orbits of Saturn, gathering data.

Buffington: And if it goes well, papers will be written on the scientific discoveries for many many years.

But if it doesn’t go well we’ve still met our engineering objective and that’s definitively disposing of our spacecraft.

Onscreen: Cassini’s destruction helps ensure that if we ever find life here, it’ll be native and not a tourist from Earth.



Digital Editor
Drew Gannon
Brent Buffington
Camera and Sound
David Arabia
Writer, Director, and Producer
Terri Randall
Jedd Ehrmann
Sound Recordists
Tim Kitz
Lauretta Molitor
David Arabia
Daniel Taub
Vicente Franco
Jason Longo


NASA/JPL/Caltech/Space Science Institute



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