NASA will destroy a US$3.26 billion Saturn probe this summer to protect an alien water world

For nearly three decades, researchers have worked to design, build, launch, and operate an unprecedented mission to explore Saturn.

Called Cassini-Huygens — or Cassini, for short — the golden nuclear-powered spacecraft launched in October 1997, fell into orbit around the gas giant in July 2004, and has been documenting the planet and its dizzying variety of moons ever since.

But all good things must come to an end. And for NASA’s US$3.26 billion probe, that day is Friday, September 15, 2017.

Researchers explained why they’re killing off their cherished spacecraft with what they call the “Grand Finale.” The manoeuvre will use up the fleeting reserves of Cassini’s fuel, putting it on a collision course with Saturn.

“Cassini’s own discoveries were its demise,” said Earl Maize, an engineer at NASA’s Jet Propulsion Laboratory (JPL) who manages the Cassini mission.

Maize was referring to a warm, saltwater ocean that Cassini found hiding beneath the icy crust of Enceladus, a large moon of Saturn that spews water into space. NASA’s probe flew through these curtain-like jets of vapour and ice in October 2015, “tasted” the material, and indirectly discovered the subsurface ocean’s composition — and it’s one that may support alien life.

“We cannot risk an inadvertent contact with that pristine body,” Maize said. “Cassini has got to be put safely away. And since we wanted to stay at Saturn, the only choice was to destroy it in some controlled fashion.”

But Maize and a collaboration of researchers from 19 nations aren’t going to let their plucky probe go down without a fight.