Cassini–Huygens
What is Cassini–Huygens?
Probes & telescopes· 1997-10-15 – 2017-09-15 (20-year mission complete). NASA and ESA's Saturn orbiter spent 13 years at the ringed planet. Its Huygens lander touched down on Titan in 2005, the first landing in the outer solar system, and Cassini revealed Enceladus's water plumes before diving into Saturn in 2017.
Spacecraft specs
| Launch | 1997-10-15 |
|---|---|
| Saturn arrival | 2004-07-01 |
| Huygens landing | 2005-01-14 |
| End | plunged into Saturn |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When did Cassini–Huygens launch?
- 1997-10-15.
- In one line, what is Cassini–Huygens?
- Probes & telescopes — NASA and ESA's Saturn orbiter spent 13 years at the ringed planet.
- What can I see of Cassini–Huygens here?
- You can see the figures and story on this page.
Measuring Saturn's day with its rings
Saturn was a planet whose day nobody knew. It has no solid surface, and its magnetic field lines up almost exactly with its rotation axis, so the radio signals that reveal other planets' rotation showed no clear period. Voyager gave 10 h 39 m, early Cassini 10 h 47 m — values differing by minutes, none trustworthy. Cassini solved it with the rings.
When Saturn's interior oscillates, the changing gravity etches faint spiral waves into the C ring. Reading those waves in thirteen years of Cassini ring images gave the interior's oscillation frequencies, and from them, in 2019, a rotation period of 10 h 33 m 38 s. This is "ring seismology" — seeing inside Saturn through its rings as seismic waves reveal Earth's interior — and the same method showed that Saturn's core is diffuse, with no sharp boundary.
The mission in depth
Cassini–Huygens paired NASA's Cassini orbiter with ESA's Huygens lander. Launched on 15 October 1997 aboard a Titan IV, it picked up speed with two Venus flybys plus Earth and Jupiter before entering Saturn orbit on 1 July 2004. At 5.7 tonnes it was the largest spacecraft ever sent to the outer solar system, powered by plutonium thermoelectric generators.
On 14 January 2005 Huygens descended through Titan's thick haze and landed — humanity's first touchdown in the outer solar system — returning pictures of river channels carved by methane and rounded blocks of ice. Cassini then flew through the water plumes erupting from Enceladus's south pole, detecting salt and organic molecules that confirmed an ocean beneath the ice, and mapped the ripples and moon-carved gaps in the rings in exquisite detail.
With fuel running out, Cassini performed its Grand Finale in 2017: 22 dives through the gap between Saturn and its rings, then a plunge into the atmosphere on 15 September, chosen so it could never contaminate possibly habitable Enceladus or Titan. Follow Saturn in the orbit view to see the moons whose orbits Cassini charted for thirteen years.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.